1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 The bttv driver 3 The bttv driver
4 =============== 4 ===============
5 5
6 bttv and sound mini howto 6 bttv and sound mini howto
7 ------------------------- 7 -------------------------
8 8
9 There are a lot of different bt848/849/878/879 9 There are a lot of different bt848/849/878/879 based boards available.
10 Making video work often is not a big deal, bec 10 Making video work often is not a big deal, because this is handled
11 completely by the bt8xx chip, which is common 11 completely by the bt8xx chip, which is common on all boards. But
12 sound is handled in slightly different ways on 12 sound is handled in slightly different ways on each board.
13 13
14 To handle the grabber boards correctly, there 14 To handle the grabber boards correctly, there is a array tvcards[] in
15 bttv-cards.c, which holds the information requ 15 bttv-cards.c, which holds the information required for each board.
16 Sound will work only, if the correct entry is 16 Sound will work only, if the correct entry is used (for video it often
17 makes no difference). The bttv driver prints 17 makes no difference). The bttv driver prints a line to the kernel
18 log, telling which card type is used. Like th 18 log, telling which card type is used. Like this one::
19 19
20 bttv0: model: BT848(Hauppauge old) [au 20 bttv0: model: BT848(Hauppauge old) [autodetected]
21 21
22 You should verify this is correct. If it isn' 22 You should verify this is correct. If it isn't, you have to pass the
23 correct board type as insmod argument, ``insmo 23 correct board type as insmod argument, ``insmod bttv card=2`` for
24 example. The file Documentation/admin-guide/m 24 example. The file Documentation/admin-guide/media/bttv-cardlist.rst has a list
25 of valid arguments for card. 25 of valid arguments for card.
26 26
27 If your card isn't listed there, you might che 27 If your card isn't listed there, you might check the source code for
28 new entries which are not listed yet. If ther 28 new entries which are not listed yet. If there isn't one for your
29 card, you can check if one of the existing ent 29 card, you can check if one of the existing entries does work for you
30 (just trial and error...). 30 (just trial and error...).
31 31
32 Some boards have an extra processor for sound 32 Some boards have an extra processor for sound to do stereo decoding
33 and other nice features. The msp34xx chips ar 33 and other nice features. The msp34xx chips are used by Hauppauge for
34 example. If your board has one, you might hav 34 example. If your board has one, you might have to load a helper
35 module like ``msp3400`` to make sound work. I 35 module like ``msp3400`` to make sound work. If there isn't one for the
36 chip used on your board: Bad luck. Start wri 36 chip used on your board: Bad luck. Start writing a new one. Well,
37 you might want to check the video4linux mailin 37 you might want to check the video4linux mailing list archive first...
38 38
39 Of course you need a correctly installed sound 39 Of course you need a correctly installed soundcard unless you have the
40 speakers connected directly to the grabber boa 40 speakers connected directly to the grabber board. Hint: check the
41 mixer settings too. ALSA for example has ever 41 mixer settings too. ALSA for example has everything muted by default.
42 42
43 43
44 How sound works in detail 44 How sound works in detail
45 ~~~~~~~~~~~~~~~~~~~~~~~~~ 45 ~~~~~~~~~~~~~~~~~~~~~~~~~
46 46
47 Still doesn't work? Looks like some driver ha 47 Still doesn't work? Looks like some driver hacking is required.
48 Below is a do-it-yourself description for you. 48 Below is a do-it-yourself description for you.
49 49
50 The bt8xx chips have 32 general purpose pins, 50 The bt8xx chips have 32 general purpose pins, and registers to control
51 these pins. One register is the output enable 51 these pins. One register is the output enable register
52 (``BT848_GPIO_OUT_EN``), it says which pins ar 52 (``BT848_GPIO_OUT_EN``), it says which pins are actively driven by the
53 bt848 chip. Another one is the data register 53 bt848 chip. Another one is the data register (``BT848_GPIO_DATA``), where
54 you can get/set the status if these pins. The 54 you can get/set the status if these pins. They can be used for input
55 and output. 55 and output.
56 56
57 Most grabber board vendors use these pins to c 57 Most grabber board vendors use these pins to control an external chip
58 which does the sound routing. But every board 58 which does the sound routing. But every board is a little different.
59 These pins are also used by some companies to 59 These pins are also used by some companies to drive remote control
60 receiver chips. Some boards use the i2c bus i 60 receiver chips. Some boards use the i2c bus instead of the gpio pins
61 to connect the mux chip. 61 to connect the mux chip.
62 62
63 As mentioned above, there is a array which hol 63 As mentioned above, there is a array which holds the required
64 information for each known board. You basical 64 information for each known board. You basically have to create a new
65 line for your board. The important fields are 65 line for your board. The important fields are these two::
66 66
67 struct tvcard 67 struct tvcard
68 { 68 {
69 [ ... ] 69 [ ... ]
70 u32 gpiomask; 70 u32 gpiomask;
71 u32 audiomux[6]; /* Tuner, Radio, exte 71 u32 audiomux[6]; /* Tuner, Radio, external, internal, mute, stereo */
72 }; 72 };
73 73
74 gpiomask specifies which pins are used to cont 74 gpiomask specifies which pins are used to control the audio mux chip.
75 The corresponding bits in the output enable re 75 The corresponding bits in the output enable register
76 (``BT848_GPIO_OUT_EN``) will be set as these p 76 (``BT848_GPIO_OUT_EN``) will be set as these pins must be driven by the
77 bt848 chip. 77 bt848 chip.
78 78
79 The ``audiomux[]`` array holds the data values 79 The ``audiomux[]`` array holds the data values for the different inputs
80 (i.e. which pins must be high/low for tuner/mu 80 (i.e. which pins must be high/low for tuner/mute/...). This will be
81 written to the data register (``BT848_GPIO_DAT 81 written to the data register (``BT848_GPIO_DATA``) to switch the audio
82 mux. 82 mux.
83 83
84 84
85 What you have to do is figure out the correct 85 What you have to do is figure out the correct values for gpiomask and
86 the audiomux array. If you have Windows and t 86 the audiomux array. If you have Windows and the drivers four your
87 card installed, you might to check out if you 87 card installed, you might to check out if you can read these registers
88 values used by the windows driver. A tool to 88 values used by the windows driver. A tool to do this is available
89 from http://btwincap.sourceforge.net/download. 89 from http://btwincap.sourceforge.net/download.html.
90 90
91 You might also dig around in the ``*.ini`` fil 91 You might also dig around in the ``*.ini`` files of the Windows applications.
92 You can have a look at the board to see which 92 You can have a look at the board to see which of the gpio pins are
93 connected at all and then start trial-and-erro 93 connected at all and then start trial-and-error ...
94 94
95 95
96 Starting with release 0.7.41 bttv has a number 96 Starting with release 0.7.41 bttv has a number of insmod options to
97 make the gpio debugging easier: 97 make the gpio debugging easier:
98 98
99 ================= ============== 99 ================= ==============================================
100 bttv_gpio=0/1 enable/disable 100 bttv_gpio=0/1 enable/disable gpio debug messages
101 gpiomask=n set the gpioma 101 gpiomask=n set the gpiomask value
102 audiomux=i,j,... set the values 102 audiomux=i,j,... set the values of the audiomux array
103 audioall=a set the values 103 audioall=a set the values of the audiomux array (one
104 value for all 104 value for all array elements, useful to check
105 out which effe 105 out which effect the particular value has).
106 ================= ============== 106 ================= ==============================================
107 107
108 The messages printed with ``bttv_gpio=1`` look 108 The messages printed with ``bttv_gpio=1`` look like this::
109 109
110 bttv0: gpio: en=00000027, out=00000024 110 bttv0: gpio: en=00000027, out=00000024 in=00ffffd8 [audio: off]
111 111
112 en = output _en_able register (BT84 112 en = output _en_able register (BT848_GPIO_OUT_EN)
113 out = _out_put bits of the data regi 113 out = _out_put bits of the data register (BT848_GPIO_DATA),
114 i.e. BT848_GPIO_DATA & BT848_G 114 i.e. BT848_GPIO_DATA & BT848_GPIO_OUT_EN
115 in = _in_put bits of the data regis 115 in = _in_put bits of the data register,
116 i.e. BT848_GPIO_DATA & ~BT848_ 116 i.e. BT848_GPIO_DATA & ~BT848_GPIO_OUT_EN
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