Hi Sakari,
On Wed, Apr 22, 2020 at 02:42:32AM +0300, Laurent Pinchart wrote:
> Hi Sakari,
>
> On Wed, Apr 22, 2020 at 12:49:58AM +0300, Sakari Ailus wrote:
> > On Sat, Apr 18, 2020 at 12:32:15PM +0200, Jacopo Mondi wrote:
> > > From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> > >
> > > While normal video/radio/vbi/swradio nodes have a proper QUERYCAP ioctl
> > > that apps can call to determine that it is indeed a V4L2 device, there
> > > is currently no equivalent for v4l-subdev nodes. Adding this ioctl will
> > > solve that, and it will allow utilities like v4l2-compliance to be used
> > > with these devices as well.
> > >
> > > SUBDEV_QUERYCAP currently returns the version and subdev_caps of the
> > > subdevice. Define as the initial set of subdev_caps the read-only or
> > > read/write flags, to signal to userspace which set of IOCTLs are
> > > available on the subdevice.
> > >
> > > Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> > > Signed-off-by: Jacopo Mondi <jacopo@xxxxxxxxxx>
> > > ---
> > > drivers/media/v4l2-core/v4l2-subdev.c | 12 ++++++++++++
> > > include/uapi/linux/v4l2-subdev.h | 15 +++++++++++++++
> > > 2 files changed, 27 insertions(+)
> > >
> > > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> > > index 1dc263c2ca0a..ca0aa54429c5 100644
> > > --- a/drivers/media/v4l2-core/v4l2-subdev.c
> > > +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> > > @@ -15,6 +15,7 @@
> > > #include <linux/types.h>
> > > #include <linux/videodev2.h>
> > > #include <linux/export.h>
> > > +#include <linux/version.h>
> > >
> > > #include <media/v4l2-ctrls.h>
> > > #include <media/v4l2-device.h>
> > > @@ -336,6 +337,17 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> > > int rval;
> > >
> > > switch (cmd) {
> > > + case VIDIOC_SUBDEV_QUERYCAP: {
> > > + struct v4l2_subdev_capability *cap = arg;
> > > +
> > > + memset(cap, 0, sizeof(*cap));
> > > + cap->version = LINUX_VERSION_CODE;
> > > + cap->subdev_caps |= ro_subdev ? V4L2_SUBDEV_CAP_RO_SUBDEV
> > > + : V4L2_SUBDEV_CAP_RW_SUBDEV;
> > > +
> > > + return 0;
> > > + }
> > > +
> > > case VIDIOC_QUERYCTRL:
> > > /*
> > > * TODO: this really should be folded into v4l2_queryctrl (this
> > > diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
> > > index 03970ce30741..0886f88be193 100644
> > > --- a/include/uapi/linux/v4l2-subdev.h
> > > +++ b/include/uapi/linux/v4l2-subdev.h
> > > @@ -155,9 +155,24 @@ struct v4l2_subdev_selection {
> > > __u32 reserved[8];
> > > };
> > >
> > > +/**
> > > + * struct v4l2_subdev_capability - subdev capabilities
> > > + * @device_caps: the subdev capabilities, see V4L2_SUBDEV_CAP_*.
> > > + */
> > > +struct v4l2_subdev_capability {
> > > + __u32 version;
> > > + __u32 subdev_caps;
> >
> > No reserved fields? Is the intent to extend this later on based on the size
> > of the IOCTL argument?
>
> That would be my preferred option.
>
That would be my preferred opinion as well, we would have versioning
and would not be tied to the available reserved fields.
