On Wed, Oct 7, 2020 at 8:21 AM Christoph Hellwig [off-list ref] wrote:

On Tue, Oct 06, 2020 at 10:56:04PM +0200, Tomasz Figa wrote:

quoted

quoted

Yes.  And make sure the API isn't implemented when VIVT caches are
used, but that isn't really different from the current interface.

Okay, thanks. Let's see if we can make necessary changes to the videobuf2.

+Sergey Senozhatsky for awareness too.

I can defer the changes a bit to see if you'd really much prefer
the former interface.  I think for now the most important thing is
that it works properly for the potential users, and the prime one is
videobuf2 for now.  drm also seems like a big potential users, but I
had a really hard time getting the developers to engage in API
development.

My initial feeling is that it should work, but we'll give you a
definitive answer once we prototype it. :)

We might actually give it a try in the USB HCD subsystem as well, to
implement usb_alloc_noncoherent(), as an optimization for drivers
which have to perform multiple random accesses to the URB buffers. I
think you might recall discussing this by the way of the pwc and
uvcvideo camera drivers.

Best regards,
Tomasz