In lists.linux.v4l, you wrote:
> Hello Gerd,
>
> > Another point: With 2.4.x and kiobufs we can do DMA to userspace now.
> > I've had a look at the code this weekend,
> > I have it working (quick+dirty hack) with bttv.
>
> Please notify us if you have some alpha-code available on the net,
> so we can see how you did it.
I've uploaded 0.7.34 yesterday which has it.
> Although it is a very good idea and gets rid of many problems,
> it is still very young and there is not much documentation
> and examples, especially for user-space-applications that
> use it.
In general userspace doesn't has to care. It makes no difference
to the application whenever the kernel copies stuff with
copy_to_user or lets write the hardware directly using kiobufs.
You can use kiobufs for normal read() syscalls if you want.
v4l ist just a special case because we are using the mmap hack
to avoid the extra memcopy from kernel to userland.
> > It is important that v4l1 and v4l2 drivers can coexist because
> > there are already alot of existing v4l1 drivers.
>
> Again, with bringing v4l2 in addition to v4l into the kernel,
> not every driver has be ready immediately.
Exactly thats why the new videodev.c needs to support both v4l1
and v4l2 drivers. So the old drivers can be converted step by
step.
Gerd
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