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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/fb/internals.rst | |
parent | Initial commit. (diff) | |
download | linux-upstream/5.10.209.tar.xz linux-upstream/5.10.209.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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-rw-r--r-- | Documentation/fb/internals.rst | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/Documentation/fb/internals.rst b/Documentation/fb/internals.rst new file mode 100644 index 000000000..696b50aa7 --- /dev/null +++ b/Documentation/fb/internals.rst @@ -0,0 +1,86 @@ +============================= +Frame Buffer device internals +============================= + +This is a first start for some documentation about frame buffer device +internals. + +Authors: + +- Geert Uytterhoeven <geert@linux-m68k.org>, 21 July 1998 +- James Simmons <jsimmons@user.sf.net>, Nov 26 2002 + +-------------------------------------------------------------------------------- + +Structures used by the frame buffer device API +============================================== + +The following structures play a role in the game of frame buffer devices. They +are defined in <linux/fb.h>. + +1. Outside the kernel (user space) + + - struct fb_fix_screeninfo + + Device independent unchangeable information about a frame buffer device and + a specific video mode. This can be obtained using the FBIOGET_FSCREENINFO + ioctl. + + - struct fb_var_screeninfo + + Device independent changeable information about a frame buffer device and a + specific video mode. This can be obtained using the FBIOGET_VSCREENINFO + ioctl, and updated with the FBIOPUT_VSCREENINFO ioctl. If you want to pan + the screen only, you can use the FBIOPAN_DISPLAY ioctl. + + - struct fb_cmap + + Device independent colormap information. You can get and set the colormap + using the FBIOGETCMAP and FBIOPUTCMAP ioctls. + + +2. Inside the kernel + + - struct fb_info + + Generic information, API and low level information about a specific frame + buffer device instance (slot number, board address, ...). + + - struct `par` + + Device dependent information that uniquely defines the video mode for this + particular piece of hardware. + + +Visuals used by the frame buffer device API +=========================================== + + +Monochrome (FB_VISUAL_MONO01 and FB_VISUAL_MONO10) +-------------------------------------------------- +Each pixel is either black or white. + + +Pseudo color (FB_VISUAL_PSEUDOCOLOR and FB_VISUAL_STATIC_PSEUDOCOLOR) +--------------------------------------------------------------------- +The whole pixel value is fed through a programmable lookup table that has one +color (including red, green, and blue intensities) for each possible pixel +value, and that color is displayed. + + +True color (FB_VISUAL_TRUECOLOR) +-------------------------------- +The pixel value is broken up into red, green, and blue fields. + + +Direct color (FB_VISUAL_DIRECTCOLOR) +------------------------------------ +The pixel value is broken up into red, green, and blue fields, each of which +are looked up in separate red, green, and blue lookup tables. + + +Grayscale displays +------------------ +Grayscale and static grayscale are special variants of pseudo color and static +pseudo color, where the red, green and blue components are always equal to +each other. |