On Thu, 14 May 2009, Hans de Goede wrote:

On 05/14/2009 06:00 PM, MK wrote:
Since I'm cross-posting this (as advised) I should introduce myself by
saying I am a neophyte C programmer getting into kernel programming by
trying to write a driver for an unsupported webcam.  So far I've gotten
the device to register and have enumerated the various interfaces.

On 05/11/2009 02:50:00 PM, Erik Andrén wrote:
First of all, this list is deprecated. Send mails to
linux-media@vger.kernel.org if you want to reach the kernel community.

Secondly, have you researched that there is no existing driver for
your camera? A good way to start would perhaps to search for the usb
id and linux in google to see if it generates some hits.

I've done this last bit already, and I just checked out gspca.  There
is a loit of listing for the vendor id, but not the product id, so I
imagine there is no point in trying any of the drivers (unless I hack
the source to accept the id string).

However, a rather unhelpful person at the linux driver backport group
informs me "not all USB video drivers are under
drivers/media/video/usbvideo/  In fact, the majority of them are not."
but then tells me I should take off and go find them myself "with a web
browser" (very nice).

Does anyone know where these drivers are located?

Most non yvc (see below) usb webcams are driven through the gspca usb
webcam driver framework. This is a v4l driver which consists of gspca-core
+ various subdrivers for a lot of bridges, see drivers/media/video/gspca


 The same person also
claims that the kernel now has support "for all devices that
follow the USB video class specification, and [sic] that the additional
23 device specific drivers in the tree* are just for non-conforming
devices".

This is correct recently the USB consortium (or whatever they are called)
have created a new spec called UVC, this is one standard protocol for all
webcams to follow. All *newer* webcams use this, but a lot of cams still
in the stores predate UVC (which stands for USB Video Class).

The first thing to find out to get your webcam supported is what kind of
bridge chip it is using, try looking at the windows driver .inf file,
typical bridges are the sonix series (often refenced to as sn9c10x or
sn9c20x), spca5xx series, zc3xx, vc032x, etc. If you see a reference
to anything like this in the windows driver .inf file (or inside dll's)
that would be good to know. Also it would be very helpful to have the usb
id of your camera.

Regards,

Hans

All of the above is excellent advice, especially in view of the fact that you say, "There is a lot of listing for the vendor id, but not the product id, so I imagine there is no point in trying any of the drivers (unless I hack the source to accept the id string)," apparently with reference to the cameras supported by gspca.

From there, things could go in several directions. First, it might
possibly be the case that it suffices only to add the camera's Vendor and Product ID to an existing driver. Or, it might be a completely different one. Or, it might be that everything can be solved but for the fact that the camera is using an undocumented and unsolved compression algorithm, which is the ultimate obstacle to overcome and also the most difficult. Perhaps in addition to the list from Hans, above, an output of lsusb or the content of the /proc/bus/usb/devices file (available if your kernel supports usbfs, otherwise not) would help.

Finally, since you say that the Vendor ID appears, it could possibly be the case that someone is already working on support for your particular camera. The matter would be more clear if the Vendor and Product ID numbers are known.


Theodore Kilgore

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