Hi Hans,
On Fri, Feb 09, 2018 at 12:56:37PM +0100, Hans Verkuil wrote:
> On 02/09/18 12:46, Sakari Ailus wrote:
> > Hi Hans,
> >
> > On Thu, Feb 08, 2018 at 09:36:44AM +0100, Hans Verkuil wrote:
> >> If the subdev did not define any controls, then return -ENOTTY if
> >> userspace attempts to call these ioctls.
> >>
> >> The control framework functions will return -EINVAL, not -ENOTTY if
> >> vfh->ctrl_handler is NULL.
> >>
> >> Several of these framework functions are also called directly from
> >> drivers, so I don't want to change the error code there.
> >>
> >> Found with vimc and v4l2-compliance.
> >>
> >> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> >
> > Thanks for the patch.
> >
> > If the handler is NULL, can there be support for the IOCTL at all? I.e.
> > should the missing handler as such result in returning -ENOTTY from these
> > functions instead of -EINVAL?
>
> I didn't dare change the control framework. Some of these v4l2_... functions
> are called by drivers and I didn't want to analyze them all. If these
> functions were only called by v4l2-ioctl.c and v4l2-subdev.c, then I'd have
> changed it in v4l2-ctrls.c, but that's not the case.
>
> It would be a useful project to replace all calls from drivers to these
> functions (they really shouldn't be used by drivers), but that is out-of-scope
> of this patch.
Is your concern that the caller could check the return value and do
something based on particular error code it gets?
Based on a quick glance there are a few tens of places these functions are
used in drivers. Some seems legitimate; the caller having another device
where a control needs to be accessed, for instance.
And if handler is NULL, -ENOTTY appears to be a more suitable return value
in a lot of the cases (and in many others it makes no difference).
I wouldn't say this is something that should hold back addressing this in
the control framework instead.
I can submit a patch if you'd prefer that instead.
>
> Regards,
>
> Hans
>
> >
> >> ---
> >> drivers/media/v4l2-core/v4l2-subdev.c | 16 ++++++++++++++++
> >> 1 file changed, 16 insertions(+)
> >>
> >> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> >> index 43fefa73e0a3..be7a19272614 100644
> >> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> >> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> >> @@ -187,27 +187,43 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> >>
> >> switch (cmd) {
> >> case VIDIOC_QUERYCTRL:
> >> + if (!vfh->ctrl_handler)
> >> + return -ENOTTY;
> >> return v4l2_queryctrl(vfh->ctrl_handler, arg);
> >>
> >> case VIDIOC_QUERY_EXT_CTRL:
> >> + if (!vfh->ctrl_handler)
> >> + return -ENOTTY;
> >> return v4l2_query_ext_ctrl(vfh->ctrl_handler, arg);
> >>
> >> case VIDIOC_QUERYMENU:
> >> + if (!vfh->ctrl_handler)
> >> + return -ENOTTY;
> >> return v4l2_querymenu(vfh->ctrl_handler, arg);
> >>
> >> case VIDIOC_G_CTRL:
> >> + if (!vfh->ctrl_handler)
> >> + return -ENOTTY;
> >> return v4l2_g_ctrl(vfh->ctrl_handler, arg);
> >>
> >> case VIDIOC_S_CTRL:
> >> + if (!vfh->ctrl_handler)
> >> + return -ENOTTY;
> >> return v4l2_s_ctrl(vfh, vfh->ctrl_handler, arg);
> >>
> >> case VIDIOC_G_EXT_CTRLS:
> >> + if (!vfh->ctrl_handler)
> >> + return -ENOTTY;
> >> return v4l2_g_ext_ctrls(vfh->ctrl_handler, arg);
> >>
> >> case VIDIOC_S_EXT_CTRLS:
> >> + if (!vfh->ctrl_handler)
> >> + return -ENOTTY;
> >> return v4l2_s_ext_ctrls(vfh, vfh->ctrl_handler, arg);
> >>
> >> case VIDIOC_TRY_EXT_CTRLS:
> >> + if (!vfh->ctrl_handler)
> >> + return -ENOTTY;
> >> return v4l2_try_ext_ctrls(vfh->ctrl_handler, arg);
> >>
> >> case VIDIOC_DQEVENT:
> >
>
--
Sakari Ailus
e-mail: sakari.ailus@xxxxxx
