Hello Manousaridis,
I want to develop drivers for a custom video board for a strongARM-linux
based platform. This board has an MPEG2 decoder and a graphics
processor. The incoming data stream will come from the network
interface. This board uses LSI 64105 and Teralogic 751 (there is no PCI
bus). I have found no drivers for them, so I have to develop the drivers
myself.
Video4linux is probably the appropriate framework for such drivers.
It depends. If you have some sort of "video output" inside your computer
(ie. your mpeg decoder stores the decoded frames in your system memory
or the framebuffer of your system), then you could use the capture
interface of Video4Linux-2 to get these frames to your application for
further processing (for example: a motion detection algorithm)
But if your decoded mpeg2 data is going directly to an analog
composite/s-video output (and there is no way for your processor to
access the decoded mpeg data), probably the Linux DVB API is more suitable.
While searching for API info, I found the following sites:
Why are there 2 variants of v4l2?
http://www.video4linux.net/
This is completly outdated. Don't use that.
> http://www.thedirks.org/v4l2/
Bill Dirks developed the first draft of Video4Linux-2. The version that
finally made it into the kernel differs in many ways. (This is noted on
the top page)
Is the API described in 'http://bytesex.org/v4l/spec/' the one I am
looking for?
Yes.
http://bytesex.org/v4l/
This is the latest resource for the Video4Linux-2 documentation (and
includes a Driver-Writing-Guide, btw...)
I want to target linux 2.4.18, but also be able to port the drivers to
more recent kernels (2.6), with minor modifications.
> If this is the case, can I use it in 2.4.18?
Kernels >= 2.4.20 include a new registration mechanism for Video4Linux
devices. There, it's possible to painlessly mix Video4Linux-1 and
Video4Linux-2 device drivers. (This wasn't able before, because
Video4Linux-2 use the standard fops mechanism for registration, while
the "old" Video4Linux-1 used a proprietary solution...)
> I found patches for more
> recent versions, but a kernel upgrade is not a trivial in my case,
> because of the arm-linux patches and the custom modifications for my
> platform.
It should be possible to backport the "videodev.c" module to 2.4.18
IMHO, if you really need 2.4.18.
But first think about if Video4Linux-2 is really the right choice for you.
Manousaridis Angelos
CU
Michael.
