Re: [PATCH RFC 2/2] staging: vc04_services: Document VCHIQ character device

Laurent Pinchart
2025-05-21T11:28:23Z

On Wed, May 21, 2025 at 01:20:54PM +0200, Greg KH wrote:
> On Sat, May 10, 2025 at 12:11:52AM +0200, Stefan Wahren wrote:
> > From: Phil Elwell <phil@raspberrypi.com>
> >
> > Document the IOCTLs for the VCHIQ character device, which provide
> > a userspace interface to access the VideoCore VPU of the
> > Raspberry Pi. Several ARM side libraries make use of it like EGL,
> > MMAL and OpenMAX.
> >
> > Link: https://github.com/raspberrypi/linux/pull/6801
> > Signed-off-by: Phil Elwell <phil@raspberrypi.com>
> > [wahrenst@gmx.net: Rewrite commit log]
> > Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
> > ---
> > .../vc04_services/Documentation/vchiq-cdev | 87 +++++++++++++++++++
> > 1 file changed, 87 insertions(+)
> > create mode 100644 drivers/staging/vc04_services/Documentation/vchiq-cdev
> >
> > diff --git a/drivers/staging/vc04_services/Documentation/vchiq-cdev b/drivers/staging/vc04_services/Documentation/vchiq-cdev
> > new file mode 100644
> > index 000000000000..99ab2567643e
> > --- /dev/null
> > +++ b/drivers/staging/vc04_services/Documentation/vchiq-cdev
> > @@ -0,0 +1,87 @@
> > +What: /dev/vchiq
> > +Date: October 2016
> > +KernelVersion: 4.9
> > +Contact: kernel-list@raspberrypi.com
> > +Description:
> > + The ioctl interface for the VCHIQ character device.
> > + Following actions are supported:
> > +
> > + * VCHIQ_IOC_CONNECT:
> > + Establish/confirm the link to the VPU peer.
>
> I understand the need, but this does not document the parameters to the
> ioctls, so it's not all that useful. How about just a normal
> documentation file with this all written out?

That would be my preference too, somewhere in
Documentation/userspace-api/.

--
Regards,

Laurent Pinchart