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media: admin-guide: improve cardlist.rst documentation
The cardlist section is important for some boards, because they may require extra modprobe parameters. Improve the docs to mention that. Thanks-to: Hans Verkuil <hverkuil-cisco@xs4all.nl> # for providing me some PCI IDs Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
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Mauro Carvalho Chehab
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.. SPDX-License-Identifier: GPL-2.0
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==========
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Cards List
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==========
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The media subsystem provide support for lots of PCI and USB drivers, plus
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platform-specific drivers. It also contains several ancillary I²C drivers.
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The platform-specific drivers are usually present on embedded systems,
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or are supported by the main board. Usually, setting them is done via
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OpenFirmware or ACPI.
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The PCI and USB drivers, however, are independent of the system's board,
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and may be added/removed by the user.
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This section contains a list of supported PCI and USB boards.
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Please notice that this list is not exaustive.
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USB drivers
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===========
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The USB boards are identified by an identification called USB ID.
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The ``lsusb`` command allows identifying the USB IDs::
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$ lsusb
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...
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Bus 001 Device 015: ID 046d:082d Logitech, Inc. HD Pro Webcam C920
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Bus 001 Device 074: ID 2040:b131 Hauppauge
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Bus 001 Device 075: ID 2013:024f PCTV Systems nanoStick T2 290e
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...
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Newer camera devices use a standard way to expose themselves as such,
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via USB Video Class. Those cameras are automatically supported by the
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``uvc-driver``.
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Older cameras and TV USB devices uses USB Vendor Classes: each vendor
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defines its own way to access the device. This section contains
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card lists for such vendor-class devices.
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While this is not as common as on PCI, sometimes the same USB ID is used
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by different products. So, several media drivers allow passing a ``card=``
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parameter, in order to setup a card number that would match the correct
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settings for an specific product type.
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.. toctree::
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:maxdepth: 1
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au0828-cardlist
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cx231xx-cardlist
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em28xx-cardlist
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tm6000-cardlist
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usbvision-cardlist
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gspca-cardlist
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PCI drivers
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===========
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The PCI boards are identified by an identification called PCI ID. The PCI ID
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is actually composed by two parts:
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- Vendor ID and device ID;
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- Subsystem ID and Subsystem device ID;
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The ``lspci -nn`` command allows identifying the vendor/device PCI IDs::
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$ lspci -nn
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...
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00:0b.0 Multimedia controller [0480]: Brooktree Corporation Bt878 Audio Capture [109e:0878] (rev 11)
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01:00.0 Multimedia video controller [0400]: Conexant Systems, Inc. CX23887/8 PCIe Broadcast Audio and Video Decoder with 3D Comb [14f1:8880] (rev 0f)
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01:01.0 Multimedia controller [0480]: Philips Semiconductors SAA7131/SAA7133/SAA7135 Video Broadcast Decoder [1131:7133] (rev d1)
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02:01.0 Multimedia video controller [0400]: Internext Compression Inc iTVC15 (CX23415) Video Decoder [4444:0803] (rev 01)
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02:02.0 Multimedia video controller [0400]: Conexant Systems, Inc. CX23418 Single-Chip MPEG-2 Encoder with Integrated Analog Video/Broadcast Audio Decoder [14f1:5b7a]
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02:03.0 Multimedia video controller [0400]: Brooktree Corporation Bt878 Video Capture [109e:036e] (rev 11)
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...
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The subsystem IDs can be obtained using ``lspci -vn``
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.. code-block:: none
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:emphasize-lines: 4
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$ lspci -vn
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...
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01:01.0 0480: 1131:7133 (rev d1)
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Subsystem: 1461:f01d
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Flags: bus master, medium devsel, latency 32, IRQ 209
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Memory at e2002000 (32-bit, non-prefetchable) [size=2K]
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Capabilities: [40] Power Management version 2
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...
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Unfortunately, sometimes the same PCI ID is used by different products.
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So, several media drivers allow passing a ``card=`` parameter, in order
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to setup a card number that would match the correct settings for an
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specific board.
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.. toctree::
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:maxdepth: 1
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bttv-cardlist
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cx18-cardlist
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cx231xx-cardlist
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cx23885-cardlist
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cx88-cardlist
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em28xx-cardlist
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ivtv-cardlist
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saa7134-cardlist
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saa7164-cardlist
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tm6000-cardlist
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I²C drivers
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===========
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The I²C (Inter-Integrated Circuit) bus is a three-wires bus used internally
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at the media cards for communication between different chips. While the bus
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is not visible to the Linux Kernel, drivers need to send and receive
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commands via the bus. The Linux Kernel driver abstraction has support to
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implement different drivers for each component inside an I²C bus, as if
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the bus were visible to the main system board.
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One of the problems with I²C devices is that sometimes the same device may
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work with different I²C hardware. This is common, for example, on devices
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that comes with a tuner for North America market, and another one for
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Europe. Some drivers have a ``tuner=`` modprobe parameter to allow using a
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different tuner number in order to address such issue.
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.. toctree::
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:maxdepth: 1
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tuner-cardlist
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usbvision-cardlist
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gspca-cardlist
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