Re: Anchor Chips V4L2 driver

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 06/03/2011 02:15 PM, Mauro Carvalho Chehab wrote:
> Em 03-06-2011 02:40, John McMaster escreveu:
>> I'd like to write a driver for an Anchor Chips (seems to be bought by
>> Cypress) USB camera Linux driver sold as an AmScope MD1800.  It seems
>> like this implies I need to write a V4L2 driver.  The camera does not
>> seem its currently supported (checked on Fedora 13 / 2.6.34.8) and I did
>> not find any information on it in mailing list archives.  Does anyone
>> know or can help me identify if a similar camera might already be
>> supported?
>
> I've no idea. Better to wait for a couple days for developers to manifest
> about that, if they're already working on it.
>
>> lsusb gives the following output:
>>
>> Bus 001 Device 111: ID 0547:4d88 Anchor Chips, Inc.
>>
>> I've started reading the "Video for Linux Two API Specification" which
>> seems like a good starting point and will move onto using source code as
>> appropriate.  Any help would be appreciated.  Thanks!
>
> You'll find other useful information at linuxtv.org wiki page. The better
> is to write it as a sub-driver for gspca. The gspca core have already all
> that it is needed for cameras. So, you'll need to focus only at the device-specific
> stuff.

I can second that you should definitely use gspca for usb webcam(ish) device
drivers. As for how to go about this, first of all grep through the windows drivers
for strings which may hint on the actual bridge chip used, chances are good
there is an already supported bridge inside the camera.

If not then make usb dumps, and start reverse engineering ...

Usually it is enough to replay the windows init sequence to get the device
to stream over either an bulk or iso endpoint, and then it is time to
figure out what that stream contains (jpeg, raw bayer, some custom format ???)

Regards,

Hans