Re: [MAINTAINER SUMMIT] User-space requirements for accelerator drivers

Laurent Pinchart
2021-09-11T00:14:22Z

Hi Dave,

On Fri, Sep 10, 2021 at 04:48:37PM -0700, Dave Hansen wrote:
> On 9/10/21 4:45 PM, Josh Triplett wrote:
> > On Sat, Sep 11, 2021 at 12:52:14AM +0200, Mauro Carvalho Chehab wrote:
> >> On media, enforcing userspace to always be open source would
> >> have been very bad, as it would prevent several videoconferencing
> >> software to exist on Linux.
> >
> > I don't think we should enforce that all userspace users of an interface
> > be Open Source. I do think we should enforce that *some* userspace user
> > of an interface be Open Source before we add the interface.
>
> Right, if there's *no* open userspace, we can't meaningfully test or
> debug the thing.
>
> Maybe we don't need a whole userspace stack for every last interface,
> but if folks can't even offer up a selftest, it's not a good sign.

It really depends on the type of driver and device. For GPUs or camera
ISPs, for instance, a selftest is pointless, a full stack is required to
be able to meaningfully test the driver and use the device as those
expose a very large custom API to userspace (usually in the form of
command buffers that contain device-specific instructions or register
values).

--
Regards,

Laurent Pinchart