From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- Documentation/fb/api.rst | 307 ++++++++++++++ Documentation/fb/arkfb.rst | 68 +++ Documentation/fb/aty128fb.rst | 75 ++++ Documentation/fb/cirrusfb.rst | 94 +++++ Documentation/fb/cmap_xfbdev.rst | 56 +++ Documentation/fb/deferred_io.rst | 79 ++++ Documentation/fb/efifb.rst | 71 ++++ Documentation/fb/ep93xx-fb.rst | 140 +++++++ Documentation/fb/fbcon.rst | 348 ++++++++++++++++ Documentation/fb/framebuffer.rst | 353 ++++++++++++++++ Documentation/fb/gxfb.rst | 54 +++ Documentation/fb/index.rst | 50 +++ Documentation/fb/intel810.rst | 287 +++++++++++++ Documentation/fb/intelfb.rst | 155 +++++++ Documentation/fb/internals.rst | 86 ++++ Documentation/fb/lxfb.rst | 55 +++ Documentation/fb/matroxfb.rst | 441 ++++++++++++++++++++ Documentation/fb/metronomefb.rst | 38 ++ Documentation/fb/modedb.rst | 172 ++++++++ Documentation/fb/pvr2fb.rst | 66 +++ Documentation/fb/pxafb.rst | 173 ++++++++ Documentation/fb/s3fb.rst | 82 ++++ Documentation/fb/sa1100fb.rst | 40 ++ Documentation/fb/sh7760fb.rst | 130 ++++++ Documentation/fb/sisfb.rst | 160 +++++++ Documentation/fb/sm501.rst | 15 + Documentation/fb/sm712fb.rst | 35 ++ Documentation/fb/sstfb.rst | 204 +++++++++ Documentation/fb/tgafb.rst | 71 ++++ Documentation/fb/tridentfb.rst | 78 ++++ Documentation/fb/udlfb.rst | 169 ++++++++ Documentation/fb/uvesafb.rst | 188 +++++++++ Documentation/fb/vesafb.rst | 190 +++++++++ Documentation/fb/viafb.modes | 870 +++++++++++++++++++++++++++++++++++++++ Documentation/fb/viafb.rst | 297 +++++++++++++ Documentation/fb/vt8623fb.rst | 64 +++ 36 files changed, 5761 insertions(+) create mode 100644 Documentation/fb/api.rst create mode 100644 Documentation/fb/arkfb.rst create mode 100644 Documentation/fb/aty128fb.rst create mode 100644 Documentation/fb/cirrusfb.rst create mode 100644 Documentation/fb/cmap_xfbdev.rst create mode 100644 Documentation/fb/deferred_io.rst create mode 100644 Documentation/fb/efifb.rst create mode 100644 Documentation/fb/ep93xx-fb.rst create mode 100644 Documentation/fb/fbcon.rst create mode 100644 Documentation/fb/framebuffer.rst create mode 100644 Documentation/fb/gxfb.rst create mode 100644 Documentation/fb/index.rst create mode 100644 Documentation/fb/intel810.rst create mode 100644 Documentation/fb/intelfb.rst create mode 100644 Documentation/fb/internals.rst create mode 100644 Documentation/fb/lxfb.rst create mode 100644 Documentation/fb/matroxfb.rst create mode 100644 Documentation/fb/metronomefb.rst create mode 100644 Documentation/fb/modedb.rst create mode 100644 Documentation/fb/pvr2fb.rst create mode 100644 Documentation/fb/pxafb.rst create mode 100644 Documentation/fb/s3fb.rst create mode 100644 Documentation/fb/sa1100fb.rst create mode 100644 Documentation/fb/sh7760fb.rst create mode 100644 Documentation/fb/sisfb.rst create mode 100644 Documentation/fb/sm501.rst create mode 100644 Documentation/fb/sm712fb.rst create mode 100644 Documentation/fb/sstfb.rst create mode 100644 Documentation/fb/tgafb.rst create mode 100644 Documentation/fb/tridentfb.rst create mode 100644 Documentation/fb/udlfb.rst create mode 100644 Documentation/fb/uvesafb.rst create mode 100644 Documentation/fb/vesafb.rst create mode 100644 Documentation/fb/viafb.modes create mode 100644 Documentation/fb/viafb.rst create mode 100644 Documentation/fb/vt8623fb.rst (limited to 'Documentation/fb') diff --git a/Documentation/fb/api.rst b/Documentation/fb/api.rst new file mode 100644 index 000000000..4f00e7196 --- /dev/null +++ b/Documentation/fb/api.rst @@ -0,0 +1,307 @@ +=========================== +The Frame Buffer Device API +=========================== + +Last revised: June 21, 2011 + + +0. Introduction +--------------- + +This document describes the frame buffer API used by applications to interact +with frame buffer devices. In-kernel APIs between device drivers and the frame +buffer core are not described. + +Due to a lack of documentation in the original frame buffer API, drivers +behaviours differ in subtle (and not so subtle) ways. This document describes +the recommended API implementation, but applications should be prepared to +deal with different behaviours. + + +1. Capabilities +--------------- + +Device and driver capabilities are reported in the fixed screen information +capabilities field:: + + struct fb_fix_screeninfo { + ... + __u16 capabilities; /* see FB_CAP_* */ + ... + }; + +Application should use those capabilities to find out what features they can +expect from the device and driver. + +- FB_CAP_FOURCC + +The driver supports the four character code (FOURCC) based format setting API. +When supported, formats are configured using a FOURCC instead of manually +specifying color components layout. + + +2. Types and visuals +-------------------- + +Pixels are stored in memory in hardware-dependent formats. Applications need +to be aware of the pixel storage format in order to write image data to the +frame buffer memory in the format expected by the hardware. + +Formats are described by frame buffer types and visuals. Some visuals require +additional information, which are stored in the variable screen information +bits_per_pixel, grayscale, red, green, blue and transp fields. + +Visuals describe how color information is encoded and assembled to create +macropixels. Types describe how macropixels are stored in memory. The following +types and visuals are supported. + +- FB_TYPE_PACKED_PIXELS + +Macropixels are stored contiguously in a single plane. If the number of bits +per macropixel is not a multiple of 8, whether macropixels are padded to the +next multiple of 8 bits or packed together into bytes depends on the visual. + +Padding at end of lines may be present and is then reported through the fixed +screen information line_length field. + +- FB_TYPE_PLANES + +Macropixels are split across multiple planes. The number of planes is equal to +the number of bits per macropixel, with plane i'th storing i'th bit from all +macropixels. + +Planes are located contiguously in memory. + +- FB_TYPE_INTERLEAVED_PLANES + +Macropixels are split across multiple planes. The number of planes is equal to +the number of bits per macropixel, with plane i'th storing i'th bit from all +macropixels. + +Planes are interleaved in memory. The interleave factor, defined as the +distance in bytes between the beginning of two consecutive interleaved blocks +belonging to different planes, is stored in the fixed screen information +type_aux field. + +- FB_TYPE_FOURCC + +Macropixels are stored in memory as described by the format FOURCC identifier +stored in the variable screen information grayscale field. + +- FB_VISUAL_MONO01 + +Pixels are black or white and stored on a number of bits (typically one) +specified by the variable screen information bpp field. + +Black pixels are represented by all bits set to 1 and white pixels by all bits +set to 0. When the number of bits per pixel is smaller than 8, several pixels +are packed together in a byte. + +FB_VISUAL_MONO01 is currently used with FB_TYPE_PACKED_PIXELS only. + +- FB_VISUAL_MONO10 + +Pixels are black or white and stored on a number of bits (typically one) +specified by the variable screen information bpp field. + +Black pixels are represented by all bits set to 0 and white pixels by all bits +set to 1. When the number of bits per pixel is smaller than 8, several pixels +are packed together in a byte. + +FB_VISUAL_MONO01 is currently used with FB_TYPE_PACKED_PIXELS only. + +- FB_VISUAL_TRUECOLOR + +Pixels are broken into red, green and blue components, and each component +indexes a read-only lookup table for the corresponding value. Lookup tables +are device-dependent, and provide linear or non-linear ramps. + +Each component is stored in a macropixel according to the variable screen +information red, green, blue and transp fields. + +- FB_VISUAL_PSEUDOCOLOR and FB_VISUAL_STATIC_PSEUDOCOLOR + +Pixel values are encoded as indices into a colormap that stores red, green and +blue components. The colormap is read-only for FB_VISUAL_STATIC_PSEUDOCOLOR +and read-write for FB_VISUAL_PSEUDOCOLOR. + +Each pixel value is stored in the number of bits reported by the variable +screen information bits_per_pixel field. + +- FB_VISUAL_DIRECTCOLOR + +Pixels are broken into red, green and blue components, and each component +indexes a programmable lookup table for the corresponding value. + +Each component is stored in a macropixel according to the variable screen +information red, green, blue and transp fields. + +- FB_VISUAL_FOURCC + +Pixels are encoded and interpreted as described by the format FOURCC +identifier stored in the variable screen information grayscale field. + + +3. Screen information +--------------------- + +Screen information are queried by applications using the FBIOGET_FSCREENINFO +and FBIOGET_VSCREENINFO ioctls. Those ioctls take a pointer to a +fb_fix_screeninfo and fb_var_screeninfo structure respectively. + +struct fb_fix_screeninfo stores device independent unchangeable information +about the frame buffer device and the current format. Those information can't +be directly modified by applications, but can be changed by the driver when an +application modifies the format:: + + struct fb_fix_screeninfo { + char id[16]; /* identification string eg "TT Builtin" */ + unsigned long smem_start; /* Start of frame buffer mem */ + /* (physical address) */ + __u32 smem_len; /* Length of frame buffer mem */ + __u32 type; /* see FB_TYPE_* */ + __u32 type_aux; /* Interleave for interleaved Planes */ + __u32 visual; /* see FB_VISUAL_* */ + __u16 xpanstep; /* zero if no hardware panning */ + __u16 ypanstep; /* zero if no hardware panning */ + __u16 ywrapstep; /* zero if no hardware ywrap */ + __u32 line_length; /* length of a line in bytes */ + unsigned long mmio_start; /* Start of Memory Mapped I/O */ + /* (physical address) */ + __u32 mmio_len; /* Length of Memory Mapped I/O */ + __u32 accel; /* Indicate to driver which */ + /* specific chip/card we have */ + __u16 capabilities; /* see FB_CAP_* */ + __u16 reserved[2]; /* Reserved for future compatibility */ + }; + +struct fb_var_screeninfo stores device independent changeable information +about a frame buffer device, its current format and video mode, as well as +other miscellaneous parameters:: + + struct fb_var_screeninfo { + __u32 xres; /* visible resolution */ + __u32 yres; + __u32 xres_virtual; /* virtual resolution */ + __u32 yres_virtual; + __u32 xoffset; /* offset from virtual to visible */ + __u32 yoffset; /* resolution */ + + __u32 bits_per_pixel; /* guess what */ + __u32 grayscale; /* 0 = color, 1 = grayscale, */ + /* >1 = FOURCC */ + struct fb_bitfield red; /* bitfield in fb mem if true color, */ + struct fb_bitfield green; /* else only length is significant */ + struct fb_bitfield blue; + struct fb_bitfield transp; /* transparency */ + + __u32 nonstd; /* != 0 Non standard pixel format */ + + __u32 activate; /* see FB_ACTIVATE_* */ + + __u32 height; /* height of picture in mm */ + __u32 width; /* width of picture in mm */ + + __u32 accel_flags; /* (OBSOLETE) see fb_info.flags */ + + /* Timing: All values in pixclocks, except pixclock (of course) */ + __u32 pixclock; /* pixel clock in ps (pico seconds) */ + __u32 left_margin; /* time from sync to picture */ + __u32 right_margin; /* time from picture to sync */ + __u32 upper_margin; /* time from sync to picture */ + __u32 lower_margin; + __u32 hsync_len; /* length of horizontal sync */ + __u32 vsync_len; /* length of vertical sync */ + __u32 sync; /* see FB_SYNC_* */ + __u32 vmode; /* see FB_VMODE_* */ + __u32 rotate; /* angle we rotate counter clockwise */ + __u32 colorspace; /* colorspace for FOURCC-based modes */ + __u32 reserved[4]; /* Reserved for future compatibility */ + }; + +To modify variable information, applications call the FBIOPUT_VSCREENINFO +ioctl with a pointer to a fb_var_screeninfo structure. If the call is +successful, the driver will update the fixed screen information accordingly. + +Instead of filling the complete fb_var_screeninfo structure manually, +applications should call the FBIOGET_VSCREENINFO ioctl and modify only the +fields they care about. + + +4. Format configuration +----------------------- + +Frame buffer devices offer two ways to configure the frame buffer format: the +legacy API and the FOURCC-based API. + + +The legacy API has been the only frame buffer format configuration API for a +long time and is thus widely used by application. It is the recommended API +for applications when using RGB and grayscale formats, as well as legacy +non-standard formats. + +To select a format, applications set the fb_var_screeninfo bits_per_pixel field +to the desired frame buffer depth. Values up to 8 will usually map to +monochrome, grayscale or pseudocolor visuals, although this is not required. + +- For grayscale formats, applications set the grayscale field to one. The red, + blue, green and transp fields must be set to 0 by applications and ignored by + drivers. Drivers must fill the red, blue and green offsets to 0 and lengths + to the bits_per_pixel value. + +- For pseudocolor formats, applications set the grayscale field to zero. The + red, blue, green and transp fields must be set to 0 by applications and + ignored by drivers. Drivers must fill the red, blue and green offsets to 0 + and lengths to the bits_per_pixel value. + +- For truecolor and directcolor formats, applications set the grayscale field + to zero, and the red, blue, green and transp fields to describe the layout of + color components in memory:: + + struct fb_bitfield { + __u32 offset; /* beginning of bitfield */ + __u32 length; /* length of bitfield */ + __u32 msb_right; /* != 0 : Most significant bit is */ + /* right */ + }; + + Pixel values are bits_per_pixel wide and are split in non-overlapping red, + green, blue and alpha (transparency) components. Location and size of each + component in the pixel value are described by the fb_bitfield offset and + length fields. Offset are computed from the right. + + Pixels are always stored in an integer number of bytes. If the number of + bits per pixel is not a multiple of 8, pixel values are padded to the next + multiple of 8 bits. + +Upon successful format configuration, drivers update the fb_fix_screeninfo +type, visual and line_length fields depending on the selected format. + + +The FOURCC-based API replaces format descriptions by four character codes +(FOURCC). FOURCCs are abstract identifiers that uniquely define a format +without explicitly describing it. This is the only API that supports YUV +formats. Drivers are also encouraged to implement the FOURCC-based API for RGB +and grayscale formats. + +Drivers that support the FOURCC-based API report this capability by setting +the FB_CAP_FOURCC bit in the fb_fix_screeninfo capabilities field. + +FOURCC definitions are located in the linux/videodev2.h header. However, and +despite starting with the V4L2_PIX_FMT_prefix, they are not restricted to V4L2 +and don't require usage of the V4L2 subsystem. FOURCC documentation is +available in Documentation/userspace-api/media/v4l/pixfmt.rst. + +To select a format, applications set the grayscale field to the desired FOURCC. +For YUV formats, they should also select the appropriate colorspace by setting +the colorspace field to one of the colorspaces listed in linux/videodev2.h and +documented in Documentation/userspace-api/media/v4l/colorspaces.rst. + +The red, green, blue and transp fields are not used with the FOURCC-based API. +For forward compatibility reasons applications must zero those fields, and +drivers must ignore them. Values other than 0 may get a meaning in future +extensions. + +Upon successful format configuration, drivers update the fb_fix_screeninfo +type, visual and line_length fields depending on the selected format. The type +and visual fields are set to FB_TYPE_FOURCC and FB_VISUAL_FOURCC respectively. diff --git a/Documentation/fb/arkfb.rst b/Documentation/fb/arkfb.rst new file mode 100644 index 000000000..aeca8773d --- /dev/null +++ b/Documentation/fb/arkfb.rst @@ -0,0 +1,68 @@ +======================================== +arkfb - fbdev driver for ARK Logic chips +======================================== + + +Supported Hardware +================== + + ARK 2000PV chip + ICS 5342 ramdac + + - only BIOS initialized VGA devices supported + - probably not working on big endian + + +Supported Features +================== + + * 4 bpp pseudocolor modes (with 18bit palette, two variants) + * 8 bpp pseudocolor mode (with 18bit palette) + * 16 bpp truecolor modes (RGB 555 and RGB 565) + * 24 bpp truecolor mode (RGB 888) + * 32 bpp truecolor mode (RGB 888) + * text mode (activated by bpp = 0) + * doublescan mode variant (not available in text mode) + * panning in both directions + * suspend/resume support + +Text mode is supported even in higher resolutions, but there is limitation to +lower pixclocks (i got maximum about 70 MHz, it is dependent on specific +hardware). This limitation is not enforced by driver. Text mode supports 8bit +wide fonts only (hardware limitation) and 16bit tall fonts (driver +limitation). Unfortunately character attributes (like color) in text mode are +broken for unknown reason, so its usefulness is limited. + +There are two 4 bpp modes. First mode (selected if nonstd == 0) is mode with +packed pixels, high nibble first. Second mode (selected if nonstd == 1) is mode +with interleaved planes (1 byte interleave), MSB first. Both modes support +8bit wide fonts only (driver limitation). + +Suspend/resume works on systems that initialize video card during resume and +if device is active (for example used by fbcon). + + +Missing Features +================ +(alias TODO list) + + * secondary (not initialized by BIOS) device support + * big endian support + * DPMS support + * MMIO support + * interlaced mode variant + * support for fontwidths != 8 in 4 bpp modes + * support for fontheight != 16 in text mode + * hardware cursor + * vsync synchronization + * feature connector support + * acceleration support (8514-like 2D) + + +Known bugs +========== + + * character attributes (and cursor) in text mode are broken + +-- +Ondrej Zajicek diff --git a/Documentation/fb/aty128fb.rst b/Documentation/fb/aty128fb.rst new file mode 100644 index 000000000..3f107718f --- /dev/null +++ b/Documentation/fb/aty128fb.rst @@ -0,0 +1,75 @@ +================= +What is aty128fb? +================= + +.. [This file is cloned from VesaFB/matroxfb] + +This is a driver for a graphic framebuffer for ATI Rage128 based devices +on Intel and PPC boxes. + +Advantages: + + * It provides a nice large console (128 cols + 48 lines with 1024x768) + without using tiny, unreadable fonts. + * You can run XF68_FBDev on top of /dev/fb0 + * Most important: boot logo :-) + +Disadvantages: + + * graphic mode is slower than text mode... but you should not notice + if you use same resolution as you used in textmode. + * still experimental. + + +How to use it? +============== + +Switching modes is done using the video=aty128fb:... modedb +boot parameter or using `fbset` program. + +See Documentation/fb/modedb.rst for more information on modedb +resolutions. + +You should compile in both vgacon (to boot if you remove your Rage128 from +box) and aty128fb (for graphics mode). You should not compile-in vesafb +unless you have primary display on non-Rage128 VBE2.0 device (see +Documentation/fb/vesafb.rst for details). + + +X11 +=== + +XF68_FBDev should generally work fine, but it is non-accelerated. As of +this document, 8 and 32bpp works fine. There have been palette issues +when switching from X to console and back to X. You will have to restart +X to fix this. + + +Configuration +============= + +You can pass kernel command line options to vesafb with +`video=aty128fb:option1,option2:value2,option3` (multiple options should +be separated by comma, values are separated from options by `:`). +Accepted options: + +========= ======================================================= +noaccel do not use acceleration engine. It is default. +accel use acceleration engine. Not finished. +vmode:x chooses PowerMacintosh video mode . Deprecated. +cmode:x chooses PowerMacintosh colour mode . Deprecated. + selects startup videomode. See modedb.txt for detailed + explanation. Default is 640x480x8bpp. +========= ======================================================= + + +Limitations +=========== + +There are known and unknown bugs, features and misfeatures. +Currently there are following known bugs: + + - This driver is still experimental and is not finished. Too many + bugs/errata to list here. + +Brad Douglas diff --git a/Documentation/fb/cirrusfb.rst b/Documentation/fb/cirrusfb.rst new file mode 100644 index 000000000..8c3e6c6cb --- /dev/null +++ b/Documentation/fb/cirrusfb.rst @@ -0,0 +1,94 @@ +============================================ +Framebuffer driver for Cirrus Logic chipsets +============================================ + +Copyright 1999 Jeff Garzik + + +.. just a little something to get people going; contributors welcome! + + +Chip families supported: + - SD64 + - Piccolo + - Picasso + - Spectrum + - Alpine (GD-543x/4x) + - Picasso4 (GD-5446) + - GD-5480 + - Laguna (GD-546x) + +Bus's supported: + - PCI + - Zorro + +Architectures supported: + - i386 + - Alpha + - PPC (Motorola Powerstack) + - m68k (Amiga) + + + +Default video modes +------------------- +At the moment, there are two kernel command line arguments supported: + +- mode:640x480 +- mode:800x600 +- mode:1024x768 + +Full support for startup video modes (modedb) will be integrated soon. + +Version 1.9.9.1 +--------------- +* Fix memory detection for 512kB case +* 800x600 mode +* Fixed timings +* Hint for AXP: Use -accel false -vyres -1 when changing resolution + + +Version 1.9.4.4 +--------------- +* Preliminary Laguna support +* Overhaul color register routines. +* Associated with the above, console colors are now obtained from a LUT + called 'palette' instead of from the VGA registers. This code was + modelled after that in atyfb and matroxfb. +* Code cleanup, add comments. +* Overhaul SR07 handling. +* Bug fixes. + + +Version 1.9.4.3 +--------------- +* Correctly set default startup video mode. +* Do not override ram size setting. Define + CLGEN_USE_HARDCODED_RAM_SETTINGS if you _do_ want to override the RAM + setting. +* Compile fixes related to new 2.3.x IORESOURCE_IO[PORT] symbol changes. +* Use new 2.3.x resource allocation. +* Some code cleanup. + + +Version 1.9.4.2 +--------------- +* Casting fixes. +* Assertions no longer cause an oops on purpose. +* Bug fixes. + + +Version 1.9.4.1 +--------------- +* Add compatibility support. Now requires a 2.1.x, 2.2.x or 2.3.x kernel. + + +Version 1.9.4 +------------- +* Several enhancements, smaller memory footprint, a few bugfixes. +* Requires kernel 2.3.14-pre1 or later. + + +Version 1.9.3 +------------- +* Bundled with kernel 2.3.14-pre1 or later. diff --git a/Documentation/fb/cmap_xfbdev.rst b/Documentation/fb/cmap_xfbdev.rst new file mode 100644 index 000000000..5db5e9787 --- /dev/null +++ b/Documentation/fb/cmap_xfbdev.rst @@ -0,0 +1,56 @@ +========================== +Understanding fbdev's cmap +========================== + +These notes explain how X's dix layer uses fbdev's cmap structures. + +- example of relevant structures in fbdev as used for a 3-bit grayscale cmap:: + + struct fb_var_screeninfo { + .bits_per_pixel = 8, + .grayscale = 1, + .red = { 4, 3, 0 }, + .green = { 0, 0, 0 }, + .blue = { 0, 0, 0 }, + } + struct fb_fix_screeninfo { + .visual = FB_VISUAL_STATIC_PSEUDOCOLOR, + } + for (i = 0; i < 8; i++) + info->cmap.red[i] = (((2*i)+1)*(0xFFFF))/16; + memcpy(info->cmap.green, info->cmap.red, sizeof(u16)*8); + memcpy(info->cmap.blue, info->cmap.red, sizeof(u16)*8); + +- X11 apps do something like the following when trying to use grayscale:: + + for (i=0; i < 8; i++) { + char colorspec[64]; + memset(colorspec,0,64); + sprintf(colorspec, "rgb:%x/%x/%x", i*36,i*36,i*36); + if (!XParseColor(outputDisplay, testColormap, colorspec, &wantedColor)) + printf("Can't get color %s\n",colorspec); + XAllocColor(outputDisplay, testColormap, &wantedColor); + grays[i] = wantedColor; + } + +There's also named equivalents like gray1..x provided you have an rgb.txt. + +Somewhere in X's callchain, this results in a call to X code that handles the +colormap. For example, Xfbdev hits the following: + +xc-011010/programs/Xserver/dix/colormap.c:: + + FindBestPixel(pentFirst, size, prgb, channel) + + dr = (long) pent->co.local.red - prgb->red; + dg = (long) pent->co.local.green - prgb->green; + db = (long) pent->co.local.blue - prgb->blue; + sq = dr * dr; + UnsignedToBigNum (sq, &sum); + BigNumAdd (&sum, &temp, &sum); + +co.local.red are entries that were brought in through FBIOGETCMAP which come +directly from the info->cmap.red that was listed above. The prgb is the rgb +that the app wants to match to. The above code is doing what looks like a least +squares matching function. That's why the cmap entries can't be set to the left +hand side boundaries of a color range. diff --git a/Documentation/fb/deferred_io.rst b/Documentation/fb/deferred_io.rst new file mode 100644 index 000000000..7300cff25 --- /dev/null +++ b/Documentation/fb/deferred_io.rst @@ -0,0 +1,79 @@ +=========== +Deferred IO +=========== + +Deferred IO is a way to delay and repurpose IO. It uses host memory as a +buffer and the MMU pagefault as a pretrigger for when to perform the device +IO. The following example may be a useful explanation of how one such setup +works: + +- userspace app like Xfbdev mmaps framebuffer +- deferred IO and driver sets up fault and page_mkwrite handlers +- userspace app tries to write to mmaped vaddress +- we get pagefault and reach fault handler +- fault handler finds and returns physical page +- we get page_mkwrite where we add this page to a list +- schedule a workqueue task to be run after a delay +- app continues writing to that page with no additional cost. this is + the key benefit. +- the workqueue task comes in and mkcleans the pages on the list, then + completes the work associated with updating the framebuffer. this is + the real work talking to the device. +- app tries to write to the address (that has now been mkcleaned) +- get pagefault and the above sequence occurs again + +As can be seen from above, one benefit is roughly to allow bursty framebuffer +writes to occur at minimum cost. Then after some time when hopefully things +have gone quiet, we go and really update the framebuffer which would be +a relatively more expensive operation. + +For some types of nonvolatile high latency displays, the desired image is +the final image rather than the intermediate stages which is why it's okay +to not update for each write that is occurring. + +It may be the case that this is useful in other scenarios as well. Paul Mundt +has mentioned a case where it is beneficial to use the page count to decide +whether to coalesce and issue SG DMA or to do memory bursts. + +Another one may be if one has a device framebuffer that is in an usual format, +say diagonally shifting RGB, this may then be a mechanism for you to allow +apps to pretend to have a normal framebuffer but reswizzle for the device +framebuffer at vsync time based on the touched pagelist. + +How to use it: (for applications) +--------------------------------- +No changes needed. mmap the framebuffer like normal and just use it. + +How to use it: (for fbdev drivers) +---------------------------------- +The following example may be helpful. + +1. Setup your structure. Eg:: + + static struct fb_deferred_io hecubafb_defio = { + .delay = HZ, + .deferred_io = hecubafb_dpy_deferred_io, + }; + +The delay is the minimum delay between when the page_mkwrite trigger occurs +and when the deferred_io callback is called. The deferred_io callback is +explained below. + +2. Setup your deferred IO callback. Eg:: + + static void hecubafb_dpy_deferred_io(struct fb_info *info, + struct list_head *pagelist) + +The deferred_io callback is where you would perform all your IO to the display +device. You receive the pagelist which is the list of pages that were written +to during the delay. You must not modify this list. This callback is called +from a workqueue. + +3. Call init:: + + info->fbdefio = &hecubafb_defio; + fb_deferred_io_init(info); + +4. Call cleanup:: + + fb_deferred_io_cleanup(info); diff --git a/Documentation/fb/efifb.rst b/Documentation/fb/efifb.rst new file mode 100644 index 000000000..6badff647 --- /dev/null +++ b/Documentation/fb/efifb.rst @@ -0,0 +1,71 @@ +============== +What is efifb? +============== + +This is a generic EFI platform driver for systems with UEFI firmware. The +system must be booted via the EFI stub for this to be usable. efifb supports +both firmware with Graphics Output Protocol (GOP) displays as well as older +systems with only Universal Graphics Adapter (UGA) displays. + +Supported Hardware +================== + +- iMac 17"/20" +- Macbook +- Macbook Pro 15"/17" +- MacMini +- ARM/ARM64/X86 systems with UEFI firmware + +How to use it? +============== + +For UGA displays, efifb does not have any kind of autodetection of your +machine. + +You have to add the following kernel parameters in your elilo.conf:: + + Macbook : + video=efifb:macbook + MacMini : + video=efifb:mini + Macbook Pro 15", iMac 17" : + video=efifb:i17 + Macbook Pro 17", iMac 20" : + video=efifb:i20 + +For GOP displays, efifb can autodetect the display's resolution and framebuffer +address, so these should work out of the box without any special parameters. + +Accepted options: + +======= =========================================================== +nowc Don't map the framebuffer write combined. This can be used + to workaround side-effects and slowdowns on other CPU cores + when large amounts of console data are written. +======= =========================================================== + +Options for GOP displays: + +mode=n + The EFI stub will set the mode of the display to mode number n if + possible. + +x[-(rgb|bgr|)] + The EFI stub will search for a display mode that matches the specified + horizontal and vertical resolution, and optionally bit depth, and set + the mode of the display to it if one is found. The bit depth can either + "rgb" or "bgr" to match specifically those pixel formats, or a number + for a mode with matching bits per pixel. + +auto + The EFI stub will choose the mode with the highest resolution (product + of horizontal and vertical resolution). If there are multiple modes + with the highest resolution, it will choose one with the highest color + depth. + +list + The EFI stub will list out all the display modes that are available. A + specific mode can then be chosen using one of the above options for the + next boot. + +Edgar Hucek diff --git a/Documentation/fb/ep93xx-fb.rst b/Documentation/fb/ep93xx-fb.rst new file mode 100644 index 000000000..1dd67f468 --- /dev/null +++ b/Documentation/fb/ep93xx-fb.rst @@ -0,0 +1,140 @@ +================================ +Driver for EP93xx LCD controller +================================ + +The EP93xx LCD controller can drive both standard desktop monitors and +embedded LCD displays. If you have a standard desktop monitor then you +can use the standard Linux video mode database. In your board file:: + + static struct ep93xxfb_mach_info some_board_fb_info = { + .num_modes = EP93XXFB_USE_MODEDB, + .bpp = 16, + }; + +If you have an embedded LCD display then you need to define a video +mode for it as follows:: + + static struct fb_videomode some_board_video_modes[] = { + { + .name = "some_lcd_name", + /* Pixel clock, porches, etc */ + }, + }; + +Note that the pixel clock value is in pico-seconds. You can use the +KHZ2PICOS macro to convert the pixel clock value. Most other values +are in pixel clocks. See Documentation/fb/framebuffer.rst for further +details. + +The ep93xxfb_mach_info structure for your board should look like the +following:: + + static struct ep93xxfb_mach_info some_board_fb_info = { + .num_modes = ARRAY_SIZE(some_board_video_modes), + .modes = some_board_video_modes, + .default_mode = &some_board_video_modes[0], + .bpp = 16, + }; + +The framebuffer device can be registered by adding the following to +your board initialisation function:: + + ep93xx_register_fb(&some_board_fb_info); + +===================== +Video Attribute Flags +===================== + +The ep93xxfb_mach_info structure has a flags field which can be used +to configure the controller. The video attributes flags are fully +documented in section 7 of the EP93xx users' guide. The following +flags are available: + +=============================== ========================================== +EP93XXFB_PCLK_FALLING Clock data on the falling edge of the + pixel clock. The default is to clock + data on the rising edge. + +EP93XXFB_SYNC_BLANK_HIGH Blank signal is active high. By + default the blank signal is active low. + +EP93XXFB_SYNC_HORIZ_HIGH Horizontal sync is active high. By + default the horizontal sync is active low. + +EP93XXFB_SYNC_VERT_HIGH Vertical sync is active high. By + default the vertical sync is active high. +=============================== ========================================== + +The physical address of the framebuffer can be controlled using the +following flags: + +=============================== ====================================== +EP93XXFB_USE_SDCSN0 Use SDCSn[0] for the framebuffer. This + is the default setting. + +EP93XXFB_USE_SDCSN1 Use SDCSn[1] for the framebuffer. + +EP93XXFB_USE_SDCSN2 Use SDCSn[2] for the framebuffer. + +EP93XXFB_USE_SDCSN3 Use SDCSn[3] for the framebuffer. +=============================== ====================================== + +================== +Platform callbacks +================== + +The EP93xx framebuffer driver supports three optional platform +callbacks: setup, teardown and blank. The setup and teardown functions +are called when the framebuffer driver is installed and removed +respectively. The blank function is called whenever the display is +blanked or unblanked. + +The setup and teardown devices pass the platform_device structure as +an argument. The fb_info and ep93xxfb_mach_info structures can be +obtained as follows:: + + static int some_board_fb_setup(struct platform_device *pdev) + { + struct ep93xxfb_mach_info *mach_info = pdev->dev.platform_data; + struct fb_info *fb_info = platform_get_drvdata(pdev); + + /* Board specific framebuffer setup */ + } + +====================== +Setting the video mode +====================== + +The video mode is set using the following syntax:: + + video=XRESxYRES[-BPP][@REFRESH] + +If the EP93xx video driver is built-in then the video mode is set on +the Linux kernel command line, for example:: + + video=ep93xx-fb:800x600-16@60 + +If the EP93xx video driver is built as a module then the video mode is +set when the module is installed:: + + modprobe ep93xx-fb video=320x240 + +============== +Screenpage bug +============== + +At least on the EP9315 there is a silicon bug which causes bit 27 of +the VIDSCRNPAGE (framebuffer physical offset) to be tied low. There is +an unofficial errata for this bug at:: + + https://marc.info/?l=linux-arm-kernel&m=110061245502000&w=2 + +By default the EP93xx framebuffer driver checks if the allocated physical +address has bit 27 set. If it does, then the memory is freed and an +error is returned. The check can be disabled by adding the following +option when loading the driver:: + + ep93xx-fb.check_screenpage_bug=0 + +In some cases it may be possible to reconfigure your SDRAM layout to +avoid this bug. See section 13 of the EP93xx users' guide for details. diff --git a/Documentation/fb/fbcon.rst b/Documentation/fb/fbcon.rst new file mode 100644 index 000000000..212f7003c --- /dev/null +++ b/Documentation/fb/fbcon.rst @@ -0,0 +1,348 @@ +======================= +The Framebuffer Console +======================= + +The framebuffer console (fbcon), as its name implies, is a text +console running on top of the framebuffer device. It has the functionality of +any standard text console driver, such as the VGA console, with the added +features that can be attributed to the graphical nature of the framebuffer. + +In the x86 architecture, the framebuffer console is optional, and +some even treat it as a toy. For other architectures, it is the only available +display device, text or graphical. + +What are the features of fbcon? The framebuffer console supports +high resolutions, varying font types, display rotation, primitive multihead, +etc. Theoretically, multi-colored fonts, blending, aliasing, and any feature +made available by the underlying graphics card are also possible. + +A. Configuration +================ + +The framebuffer console can be enabled by using your favorite kernel +configuration tool. It is under Device Drivers->Graphics Support-> +Console display driver support->Framebuffer Console Support. +Select 'y' to compile support statically or 'm' for module support. The +module will be fbcon. + +In order for fbcon to activate, at least one framebuffer driver is +required, so choose from any of the numerous drivers available. For x86 +systems, they almost universally have VGA cards, so vga16fb and vesafb will +always be available. However, using a chipset-specific driver will give you +more speed and features, such as the ability to change the video mode +dynamically. + +To display the penguin logo, choose any logo available in Graphics +support->Bootup logo. + +Also, you will need to select at least one compiled-in font, but if +you don't do anything, the kernel configuration tool will select one for you, +usually an 8x16 font. + +GOTCHA: A common bug report is enabling the framebuffer without enabling the +framebuffer console. Depending on the driver, you may get a blanked or +garbled display, but the system still boots to completion. If you are +fortunate to have a driver that does not alter the graphics chip, then you +will still get a VGA console. + +B. Loading +========== + +Possible scenarios: + +1. Driver and fbcon are compiled statically + + Usually, fbcon will automatically take over your console. The notable + exception is vesafb. It needs to be explicitly activated with the + vga= boot option parameter. + +2. Driver is compiled statically, fbcon is compiled as a module + + Depending on the driver, you either get a standard console, or a + garbled display, as mentioned above. To get a framebuffer console, + do a 'modprobe fbcon'. + +3. Driver is compiled as a module, fbcon is compiled statically + + You get your standard console. Once the driver is loaded with + 'modprobe xxxfb', fbcon automatically takes over the console with + the possible exception of using the fbcon=map:n option. See below. + +4. Driver and fbcon are compiled as a module. + + You can load them in any order. Once both are loaded, fbcon will take + over the console. + +C. Boot options + + The framebuffer console has several, largely unknown, boot options + that can change its behavior. + +1. fbcon=font: + + Select the initial font to use. The value 'name' can be any of the + compiled-in fonts: 10x18, 6x10, 6x8, 7x14, Acorn8x8, MINI4x6, + PEARL8x8, ProFont6x11, SUN12x22, SUN8x16, TER16x32, VGA8x16, VGA8x8. + + Note, not all drivers can handle font with widths not divisible by 8, + such as vga16fb. + + +2. fbcon=map:<0123> + + This is an interesting option. It tells which driver gets mapped to + which console. The value '0123' is a sequence that gets repeated until + the total length is 64 which is the number of consoles available. In + the above example, it is expanded to 012301230123... and the mapping + will be:: + + tty | 1 2 3 4 5 6 7 8 9 ... + fb | 0 1 2 3 0 1 2 3 0 ... + + ('cat /proc/fb' should tell you what the fb numbers are) + + One side effect that may be useful is using a map value that exceeds + the number of loaded fb drivers. For example, if only one driver is + available, fb0, adding fbcon=map:1 tells fbcon not to take over the + console. + + Later on, when you want to map the console the to the framebuffer + device, you can use the con2fbmap utility. + +3. fbcon=vc:- + + This option tells fbcon to take over only a range of consoles as + specified by the values 'n1' and 'n2'. The rest of the consoles + outside the given range will still be controlled by the standard + console driver. + + NOTE: For x86 machines, the standard console is the VGA console which + is typically located on the same video card. Thus, the consoles that + are controlled by the VGA console will be garbled. + +4. fbcon=rotate: + + This option changes the orientation angle of the console display. The + value 'n' accepts the following: + + - 0 - normal orientation (0 degree) + - 1 - clockwise orientation (90 degrees) + - 2 - upside down orientation (180 degrees) + - 3 - counterclockwise orientation (270 degrees) + + The angle can be changed anytime afterwards by 'echoing' the same + numbers to any one of the 2 attributes found in + /sys/class/graphics/fbcon: + + - rotate - rotate the display of the active console + - rotate_all - rotate the display of all consoles + + Console rotation will only become available if Framebuffer Console + Rotation support is compiled in your kernel. + + NOTE: This is purely console rotation. Any other applications that + use the framebuffer will remain at their 'normal' orientation. + Actually, the underlying fb driver is totally ignorant of console + rotation. + +5. fbcon=margin: + + This option specifies the color of the margins. The margins are the + leftover area at the right and the bottom of the screen that are not + used by text. By default, this area will be black. The 'color' value + is an integer number that depends on the framebuffer driver being used. + +6. fbcon=nodefer + + If the kernel is compiled with deferred fbcon takeover support, normally + the framebuffer contents, left in place by the firmware/bootloader, will + be preserved until there actually is some text is output to the console. + This option causes fbcon to bind immediately to the fbdev device. + +7. fbcon=logo-pos: + + The only possible 'location' is 'center' (without quotes), and when + given, the bootup logo is moved from the default top-left corner + location to the center of the framebuffer. If more than one logo is + displayed due to multiple CPUs, the collected line of logos is moved + as a whole. + +8. fbcon=logo-count: + + The value 'n' overrides the number of bootup logos. 0 disables the + logo, and -1 gives the default which is the number of online CPUs. + +C. Attaching, Detaching and Unloading + +Before going on to how to attach, detach and unload the framebuffer console, an +illustration of the dependencies may help. + +The console layer, as with most subsystems, needs a driver that interfaces with +the hardware. Thus, in a VGA console:: + + console ---> VGA driver ---> hardware. + +Assuming the VGA driver can be unloaded, one must first unbind the VGA driver +from the console layer before unloading the driver. The VGA driver cannot be +unloaded if it is still bound to the console layer. (See +Documentation/driver-api/console.rst for more information). + +This is more complicated in the case of the framebuffer console (fbcon), +because fbcon is an intermediate layer between the console and the drivers:: + + console ---> fbcon ---> fbdev drivers ---> hardware + +The fbdev drivers cannot be unloaded if bound to fbcon, and fbcon cannot +be unloaded if it's bound to the console layer. + +So to unload the fbdev drivers, one must first unbind fbcon from the console, +then unbind the fbdev drivers from fbcon. Fortunately, unbinding fbcon from +the console layer will automatically unbind framebuffer drivers from +fbcon. Thus, there is no need to explicitly unbind the fbdev drivers from +fbcon. + +So, how do we unbind fbcon from the console? Part of the answer is in +Documentation/driver-api/console.rst. To summarize: + +Echo a value to the bind file that represents the framebuffer console +driver. So assuming vtcon1 represents fbcon, then:: + + echo 1 > /sys/class/vtconsole/vtcon1/bind - attach framebuffer console to + console layer + echo 0 > /sys/class/vtconsole/vtcon1/bind - detach framebuffer console from + console layer + +If fbcon is detached from the console layer, your boot console driver (which is +usually VGA text mode) will take over. A few drivers (rivafb and i810fb) will +restore VGA text mode for you. With the rest, before detaching fbcon, you +must take a few additional steps to make sure that your VGA text mode is +restored properly. The following is one of the several methods that you can do: + +1. Download or install vbetool. This utility is included with most + distributions nowadays, and is usually part of the suspend/resume tool. + +2. In your kernel configuration, ensure that CONFIG_FRAMEBUFFER_CONSOLE is set + to 'y' or 'm'. Enable one or more of your favorite framebuffer drivers. + +3. Boot into text mode and as root run:: + + vbetool vbestate save > + + The above command saves the register contents of your graphics + hardware to . You need to do this step only once as + the state file can be reused. + +4. If fbcon is compiled as a module, load fbcon by doing:: + + modprobe fbcon + +5. Now to detach fbcon:: + + vbetool vbestate restore < && \ + echo 0 > /sys/class/vtconsole/vtcon1/bind + +6. That's it, you're back to VGA mode. And if you compiled fbcon as a module, + you can unload it by 'rmmod fbcon'. + +7. To reattach fbcon:: + + echo 1 > /sys/class/vtconsole/vtcon1/bind + +8. Once fbcon is unbound, all drivers registered to the system will also +become unbound. This means that fbcon and individual framebuffer drivers +can be unloaded or reloaded at will. Reloading the drivers or fbcon will +automatically bind the console, fbcon and the drivers together. Unloading +all the drivers without unloading fbcon will make it impossible for the +console to bind fbcon. + +Notes for vesafb users: +======================= + +Unfortunately, if your bootline includes a vga=xxx parameter that sets the +hardware in graphics mode, such as when loading vesafb, vgacon will not load. +Instead, vgacon will replace the default boot console with dummycon, and you +won't get any display after detaching fbcon. Your machine is still alive, so +you can reattach vesafb. However, to reattach vesafb, you need to do one of +the following: + +Variation 1: + + a. Before detaching fbcon, do:: + + vbetool vbemode save > # do once for each vesafb mode, + # the file can be reused + + b. Detach fbcon as in step 5. + + c. Attach fbcon:: + + vbetool vbestate restore < && \ + echo 1 > /sys/class/vtconsole/vtcon1/bind + +Variation 2: + + a. Before detaching fbcon, do:: + + echo > /sys/class/tty/console/bind + + vbetool vbemode get + + b. Take note of the mode number + + b. Detach fbcon as in step 5. + + c. Attach fbcon:: + + vbetool vbemode set && \ + echo 1 > /sys/class/vtconsole/vtcon1/bind + +Samples: +======== + +Here are 2 sample bash scripts that you can use to bind or unbind the +framebuffer console driver if you are on an X86 box:: + + #!/bin/bash + # Unbind fbcon + + # Change this to where your actual vgastate file is located + # Or Use VGASTATE=$1 to indicate the state file at runtime + VGASTATE=/tmp/vgastate + + # path to vbetool + VBETOOL=/usr/local/bin + + + for (( i = 0; i < 16; i++)) + do + if test -x /sys/class/vtconsole/vtcon$i; then + if [ `cat /sys/class/vtconsole/vtcon$i/name | grep -c "frame buffer"` \ + = 1 ]; then + if test -x $VBETOOL/vbetool; then + echo Unbinding vtcon$i + $VBETOOL/vbetool vbestate restore < $VGASTATE + echo 0 > /sys/class/vtconsole/vtcon$i/bind + fi + fi + fi + done + +--------------------------------------------------------------------------- + +:: + + #!/bin/bash + # Bind fbcon + + for (( i = 0; i < 16; i++)) + do + if test -x /sys/class/vtconsole/vtcon$i; then + if [ `cat /sys/class/vtconsole/vtcon$i/name | grep -c "frame buffer"` \ + = 1 ]; then + echo Unbinding vtcon$i + echo 1 > /sys/class/vtconsole/vtcon$i/bind + fi + fi + done + +Antonino Daplas diff --git a/Documentation/fb/framebuffer.rst b/Documentation/fb/framebuffer.rst new file mode 100644 index 000000000..7fe087310 --- /dev/null +++ b/Documentation/fb/framebuffer.rst @@ -0,0 +1,353 @@ +======================= +The Frame Buffer Device +======================= + +Last revised: May 10, 2001 + + +0. Introduction +--------------- + +The frame buffer device provides an abstraction for the graphics hardware. It +represents the frame buffer of some video hardware and allows application +software to access the graphics hardware through a well-defined interface, so +the software doesn't need to know anything about the low-level (hardware +register) stuff. + +The device is accessed through special device nodes, usually located in the +/dev directory, i.e. /dev/fb*. + + +1. User's View of /dev/fb* +-------------------------- + +From the user's point of view, the frame buffer device looks just like any +other device in /dev. It's a character device using major 29; the minor +specifies the frame buffer number. + +By convention, the following device nodes are used (numbers indicate the device +minor numbers):: + + 0 = /dev/fb0 First frame buffer + 1 = /dev/fb1 Second frame buffer + ... + 31 = /dev/fb31 32nd frame buffer + +For backwards compatibility, you may want to create the following symbolic +links:: + + /dev/fb0current -> fb0 + /dev/fb1current -> fb1 + +and so on... + +The frame buffer devices are also `normal` memory devices, this means, you can +read and write their contents. You can, for example, make a screen snapshot by:: + + cp /dev/fb0 myfile + +There also can be more than one frame buffer at a time, e.g. if you have a +graphics card in addition to the built-in hardware. The corresponding frame +buffer devices (/dev/fb0 and /dev/fb1 etc.) work independently. + +Application software that uses the frame buffer device (e.g. the X server) will +use /dev/fb0 by default (older software uses /dev/fb0current). You can specify +an alternative frame buffer device by setting the environment variable +$FRAMEBUFFER to the path name of a frame buffer device, e.g. (for sh/bash +users):: + + export FRAMEBUFFER=/dev/fb1 + +or (for csh users):: + + setenv FRAMEBUFFER /dev/fb1 + +After this the X server will use the second frame buffer. + + +2. Programmer's View of /dev/fb* +-------------------------------- + +As you already know, a frame buffer device is a memory device like /dev/mem and +it has the same features. You can read it, write it, seek to some location in +it and mmap() it (the main usage). The difference is just that the memory that +appears in the special file is not the whole memory, but the frame buffer of +some video hardware. + +/dev/fb* also allows several ioctls on it, by which lots of information about +the hardware can be queried and set. The color map handling works via ioctls, +too. Look into for more information on what ioctls exist and on +which data structures they work. Here's just a brief overview: + + - You can request unchangeable information about the hardware, like name, + organization of the screen memory (planes, packed pixels, ...) and address + and length of the screen memory. + + - You can request and change variable information about the hardware, like + visible and virtual geometry, depth, color map format, timing, and so on. + If you try to change that information, the driver maybe will round up some + values to meet the hardware's capabilities (or return EINVAL if that isn't + possible). + + - You can get and set parts of the color map. Communication is done with 16 + bits per color part (red, green, blue, transparency) to support all + existing hardware. The driver does all the computations needed to apply + it to the hardware (round it down to less bits, maybe throw away + transparency). + +All this hardware abstraction makes the implementation of application programs +easier and more portable. E.g. the X server works completely on /dev/fb* and +thus doesn't need to know, for example, how the color registers of the concrete +hardware are organized. XF68_FBDev is a general X server for bitmapped, +unaccelerated video hardware. The only thing that has to be built into +application programs is the screen organization (bitplanes or chunky pixels +etc.), because it works on the frame buffer image data directly. + +For the future it is planned that frame buffer drivers for graphics cards and +the like can be implemented as kernel modules that are loaded at runtime. Such +a driver just has to call register_framebuffer() and supply some functions. +Writing and distributing such drivers independently from the kernel will save +much trouble... + + +3. Frame Buffer Resolution Maintenance +-------------------------------------- + +Frame buffer resolutions are maintained using the utility `fbset`. It can +change the video mode properties of a frame buffer device. Its main usage is +to change the current video mode, e.g. during boot up in one of your `/etc/rc.*` +or `/etc/init.d/*` files. + +Fbset uses a video mode database stored in a configuration file, so you can +easily add your own modes and refer to them with a simple identifier. + + +4. The X Server +--------------- + +The X server (XF68_FBDev) is the most notable application program for the frame +buffer device. Starting with XFree86 release 3.2, the X server is part of +XFree86 and has 2 modes: + + - If the `Display` subsection for the `fbdev` driver in the /etc/XF86Config + file contains a:: + + Modes "default" + + line, the X server will use the scheme discussed above, i.e. it will start + up in the resolution determined by /dev/fb0 (or $FRAMEBUFFER, if set). You + still have to specify the color depth (using the Depth keyword) and virtual + resolution (using the Virtual keyword) though. This is the default for the + configuration file supplied with XFree86. It's the most simple + configuration, but it has some limitations. + + - Therefore it's also possible to specify resolutions in the /etc/XF86Config + file. This allows for on-the-fly resolution switching while retaining the + same virtual desktop size. The frame buffer device that's used is still + /dev/fb0current (or $FRAMEBUFFER), but the available resolutions are + defined by /etc/XF86Config now. The disadvantage is that you have to + specify the timings in a different format (but `fbset -x` may help). + +To tune a video mode, you can use fbset or xvidtune. Note that xvidtune doesn't +work 100% with XF68_FBDev: the reported clock values are always incorrect. + + +5. Video Mode Timings +--------------------- + +A monitor draws an image on the screen by using an electron beam (3 electron +beams for color models, 1 electron beam for monochrome monitors). The front of +the screen is covered by a pattern of colored phosphors (pixels). If a phosphor +is hit by an electron, it emits a photon and thus becomes visible. + +The electron beam draws horizontal lines (scanlines) from left to right, and +from the top to the bottom of the screen. By modifying the intensity of the +electron beam, pixels with various colors and intensities can be shown. + +After each scanline the electron beam has to move back to the left side of the +screen and to the next line: this is called the horizontal retrace. After the +whole screen (frame) was painted, the beam moves back to the upper left corner: +this is called the vertical retrace. During both the horizontal and vertical +retrace, the electron beam is turned off (blanked). + +The speed at which the electron beam paints the pixels is determined by the +dotclock in the graphics board. For a dotclock of e.g. 28.37516 MHz (millions +of cycles per second), each pixel is 35242 ps (picoseconds) long:: + + 1/(28.37516E6 Hz) = 35.242E-9 s + +If the screen resolution is 640x480, it will take:: + + 640*35.242E-9 s = 22.555E-6 s + +to paint the 640 (xres) pixels on one scanline. But the horizontal retrace +also takes time (e.g. 272 `pixels`), so a full scanline takes:: + + (640+272)*35.242E-9 s = 32.141E-6 s + +We'll say that the horizontal scanrate is about 31 kHz:: + + 1/(32.141E-6 s) = 31.113E3 Hz + +A full screen counts 480 (yres) lines, but we have to consider the vertical +retrace too (e.g. 49 `lines`). So a full screen will take:: + + (480+49)*32.141E-6 s = 17.002E-3 s + +The vertical scanrate is about 59 Hz:: + + 1/(17.002E-3 s) = 58.815 Hz + +This means the screen data is refreshed about 59 times per second. To have a +stable picture without visible flicker, VESA recommends a vertical scanrate of +at least 72 Hz. But the perceived flicker is very human dependent: some people +can use 50 Hz without any trouble, while I'll notice if it's less than 80 Hz. + +Since the monitor doesn't know when a new scanline starts, the graphics board +will supply a synchronization pulse (horizontal sync or hsync) for each +scanline. Similarly it supplies a synchronization pulse (vertical sync or +vsync) for each new frame. The position of the image on the screen is +influenced by the moments at which the synchronization pulses occur. + +The following picture summarizes all timings. The horizontal retrace time is +the sum of the left margin, the right margin and the hsync length, while the +vertical retrace time is the sum of the upper margin, the lower margin and the +vsync length:: + + +----------+---------------------------------------------+----------+-------+ + | | ↑ | | | + | | |upper_margin | | | + | | ↓ | | | + +----------###############################################----------+-------+ + | # ↑ # | | + | # | # | | + | # | # | | + | # | # | | + | left # | # right | hsync | + | margin # | xres # margin | len | + |<-------->#<---------------+--------------------------->#<-------->|<----->| + | # | # | | + | # | # | | + | # | # | | + | # |yres # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # | # | | + | # ↓ # | | + +----------###############################################----------+-------+ + | | ↑ | | | + | | |lower_margin | | | + | | ↓ | | | + +----------+---------------------------------------------+----------+-------+ + | | ↑ | | | + | | |vsync_len | | | + | | ↓ | | | + +----------+---------------------------------------------+----------+-------+ + +The frame buffer device expects all horizontal timings in number of dotclocks +(in picoseconds, 1E-12 s), and vertical timings in number of scanlines. + + +6. Converting XFree86 timing values info frame buffer device timings +-------------------------------------------------------------------- + +An XFree86 mode line consists of the following fields:: + + "800x600" 50 800 856 976 1040 600 637 643 666 + < name > DCF HR SH1 SH2 HFL VR SV1 SV2 VFL + +The frame buffer device uses the following fields: + + - pixclock: pixel clock in ps (pico seconds) + - left_margin: time from sync to picture + - right_margin: time from picture to sync + - upper_margin: time from sync to picture + - lower_margin: time from picture to sync + - hsync_len: length of horizontal sync + - vsync_len: length of vertical sync + +1) Pixelclock: + + xfree: in MHz + + fb: in picoseconds (ps) + + pixclock = 1000000 / DCF + +2) horizontal timings: + + left_margin = HFL - SH2 + + right_margin = SH1 - HR + + hsync_len = SH2 - SH1 + +3) vertical timings: + + upper_margin = VFL - SV2 + + lower_margin = SV1 - VR + + vsync_len = SV2 - SV1 + +Good examples for VESA timings can be found in the XFree86 source tree, +under "xc/programs/Xserver/hw/xfree86/doc/modeDB.txt". + + +7. References +------------- + +For more specific information about the frame buffer device and its +applications, please refer to the Linux-fbdev website: + + http://linux-fbdev.sourceforge.net/ + +and to the following documentation: + + - The manual pages for fbset: fbset(8), fb.modes(5) + - The manual pages for XFree86: XF68_FBDev(1), XF86Config(4/5) + - The mighty kernel sources: + + - linux/drivers/video/ + - linux/include/linux/fb.h + - linux/include/video/ + + + +8. Mailing list +--------------- + +There is a frame buffer device related mailing list at kernel.org: +linux-fbdev@vger.kernel.org. + +Point your web browser to http://sourceforge.net/projects/linux-fbdev/ for +subscription information and archive browsing. + + +9. Downloading +-------------- + +All necessary files can be found at + + ftp://ftp.uni-erlangen.de/pub/Linux/LOCAL/680x0/ + +and on its mirrors. + +The latest version of fbset can be found at + + http://www.linux-fbdev.org/ + + +10. Credits +----------- + +This readme was written by Geert Uytterhoeven, partly based on the original +`X-framebuffer.README` by Roman Hodek and Martin Schaller. Section 6 was +provided by Frank Neumann. + +The frame buffer device abstraction was designed by Martin Schaller. diff --git a/Documentation/fb/gxfb.rst b/Documentation/fb/gxfb.rst new file mode 100644 index 000000000..5738709bc --- /dev/null +++ b/Documentation/fb/gxfb.rst @@ -0,0 +1,54 @@ +============= +What is gxfb? +============= + +.. [This file is cloned from VesaFB/aty128fb] + +This is a graphics framebuffer driver for AMD Geode GX2 based processors. + +Advantages: + + * No need to use AMD's VSA code (or other VESA emulation layer) in the + BIOS. + * It provides a nice large console (128 cols + 48 lines with 1024x768) + without using tiny, unreadable fonts. + * You can run XF68_FBDev on top of /dev/fb0 + * Most important: boot logo :-) + +Disadvantages: + + * graphic mode is slower than text mode... + + +How to use it? +============== + +Switching modes is done using gxfb.mode_option=... boot +parameter or using `fbset` program. + +See Documentation/fb/modedb.rst for more information on modedb +resolutions. + + +X11 +=== + +XF68_FBDev should generally work fine, but it is non-accelerated. + + +Configuration +============= + +You can pass kernel command line options to gxfb with gxfb.