Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 116 insertions, 0 deletions

diff --git a/Documentation/driver-api/media/drivers/bttv-devel.rst b/Documentation/driver-api/media/drivers/bttv-devel.rst
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+.. SPDX-License-Identifier: GPL-2.0
+
+The bttv driver
+===============
+
+bttv and sound mini howto
+-------------------------
+
+There are a lot of different bt848/849/878/879 based boards available.
+Making video work often is not a big deal, because this is handled
+completely by the bt8xx chip, which is common on all boards.  But
+sound is handled in slightly different ways on each board.
+
+To handle the grabber boards correctly, there is a array tvcards[] in
+bttv-cards.c, which holds the information required for each board.
+Sound will work only, if the correct entry is used (for video it often
+makes no difference).  The bttv driver prints a line to the kernel
+log, telling which card type is used.  Like this one::
+
+	bttv0: model: BT848(Hauppauge old) [autodetected]
+
+You should verify this is correct.  If it isn't, you have to pass the
+correct board type as insmod argument, ``insmod bttv card=2`` for
+example.  The file :doc:`/admin-guide/media/bttv-cardlist` has a list
+of valid arguments for card.
+
+If your card isn't listed there, you might check the source code for
+new entries which are not listed yet.  If there isn't one for your
+card, you can check if one of the existing entries does work for you
+(just trial and error...).
+
+Some boards have an extra processor for sound to do stereo decoding
+and other nice features.  The msp34xx chips are used by Hauppauge for
+example.  If your board has one, you might have to load a helper
+module like ``msp3400`` to make sound work.  If there isn't one for the
+chip used on your board:  Bad luck.  Start writing a new one.  Well,
+you might want to check the video4linux mailing list archive first...
+
+Of course you need a correctly installed soundcard unless you have the
+speakers connected directly to the grabber board.  Hint: check the
+mixer settings too.  ALSA for example has everything muted by default.
+
+
+How sound works in detail
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Still doesn't work?  Looks like some driver hacking is required.
+Below is a do-it-yourself description for you.
+
+The bt8xx chips have 32 general purpose pins, and registers to control
+these pins.  One register is the output enable register
+(``BT848_GPIO_OUT_EN``), it says which pins are actively driven by the
+bt848 chip.  Another one is the data register (``BT848_GPIO_DATA``), where
+you can get/set the status if these pins.  They can be used for input
+and output.
+
+Most grabber board vendors use these pins to control an external chip
+which does the sound routing.  But every board is a little different.
+These pins are also used by some companies to drive remote control
+receiver chips.  Some boards use the i2c bus instead of the gpio pins
+to connect the mux chip.
+
+As mentioned above, there is a array which holds the required
+information for each known board.  You basically have to create a new
+line for your board.  The important fields are these two::
+
+  struct tvcard
+  {
+	[ ... ]
+	u32 gpiomask;
+	u32 audiomux[6]; /* Tuner, Radio, external, internal, mute, stereo */
+  };
+
+gpiomask specifies which pins are used to control the audio mux chip.
+The corresponding bits in the output enable register
+(``BT848_GPIO_OUT_EN``) will be set as these pins must be driven by the
+bt848 chip.
+
+The ``audiomux[]`` array holds the data values for the different inputs
+(i.e. which pins must be high/low for tuner/mute/...).  This will be
+written to the data register (``BT848_GPIO_DATA``) to switch the audio
+mux.
+
+
+What you have to do is figure out the correct values for gpiomask and
+the audiomux array.  If you have Windows and the drivers four your
+card installed, you might to check out if you can read these registers
+values used by the windows driver.  A tool to do this is available
+from http://btwincap.sourceforge.net/download.html.
+
+You might also dig around in the ``*.ini`` files of the Windows applications.
+You can have a look at the board to see which of the gpio pins are
+connected at all and then start trial-and-error ...
+
+
+Starting with release 0.7.41 bttv has a number of insmod options to
+make the gpio debugging easier:
+
+	=================	==============================================
+	bttv_gpio=0/1		enable/disable gpio debug messages
+	gpiomask=n		set the gpiomask value
+	audiomux=i,j,...	set the values of the audiomux array
+	audioall=a		set the values of the audiomux array (one
+				value for all array elements, useful to check
+				out which effect the particular value has).
+	=================	==============================================
+
+The messages printed with ``bttv_gpio=1`` look like this::
+
+	bttv0: gpio: en=00000027, out=00000024 in=00ffffd8 [audio: off]
+
+	en  =	output _en_able register (BT848_GPIO_OUT_EN)
+	out =	_out_put bits of the data register (BT848_GPIO_DATA),
+		i.e. BT848_GPIO_DATA & BT848_GPIO_OUT_EN
+	in  = 	_in_put bits of the data register,
+		i.e. BT848_GPIO_DATA & ~BT848_GPIO_OUT_EN