On Mon, Dec 18, 2017 at 05:27:04PM -0200, Mauro Carvalho Chehab wrote:
> Em Mon, 9 Oct 2017 23:23:56 +0300
> Sakari Ailus <sakari.ailus@xxxxxx> escreveu:
>
> > Hi Mauro,
> >
> > On Mon, Oct 09, 2017 at 07:19:21AM -0300, Mauro Carvalho Chehab wrote:
> > > The __V4L2_SUBDEV_MK_GET_TRY() macro is used to define
> > > 3 functions that have the same arguments. The code of those
> > > functions is simple enough to just declare them, de-obfuscating
> > > the code.
> > >
> > > While here, replace BUG_ON() by WARN_ON() as there's no reason
> > > why to panic the Kernel if this fails.
> >
> > BUG_ON() might actually be a better idea as this will lead to memory
> > corruption. I presume it's not been hit often.
>
> Well, let's then change the code to:
>
> if (WARN_ON(pad >= sd->entity.num_pads))
> return -EINVAL;
>
> This way, it won't try to use an invalid value. As those are default
> handlers for ioctls, userspace should be able to handle it.
Another approach would be to return the entry for a valid pad. Few if any
drivers perform error handling on the value returned for the simple reason
that they know how many pads their own entities have.
>
> >
> > That said, I, too, favour WARN_ON() in this case. In case pad exceeds the
> > number of pads, then zero could be used, for instance. The only real
> > problem comes if there were no pads to begin with. The callers of these
> > functions also don't expect to receive NULL. Another option would be to
> > define a static, dummy variable for the purpose that would be at least safe
> > to access. Or we could just use the dummy entry whenever the pad isn't
> > valid.
> >
> > This will make the functions more complex and I might just keep the
> > original macro. Even grep works on it nowadays.
> >
> > >
> > > Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
> > > ---
> > > include/media/v4l2-subdev.h | 37 +++++++++++++++++++++++++------------
> > > 1 file changed, 25 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> > > index 1f34045f07ce..35c4476c56ee 100644
> > > --- a/include/media/v4l2-subdev.h
> > > +++ b/include/media/v4l2-subdev.h
> > > @@ -897,19 +897,32 @@ struct v4l2_subdev_fh {
> > > container_of(fh, struct v4l2_subdev_fh, vfh)
> > >
> > > #if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
> > > -#define __V4L2_SUBDEV_MK_GET_TRY(rtype, fun_name, field_name) \
> > > - static inline struct rtype * \
> > > - fun_name(struct v4l2_subdev *sd, \
> > > - struct v4l2_subdev_pad_config *cfg, \
> > > - unsigned int pad) \
> > > - { \
> > > - BUG_ON(pad >= sd->entity.num_pads); \
> > > - return &cfg[pad].field_name; \
> > > - }
> > > +static inline struct v4l2_mbus_framefmt
> > > +*v4l2_subdev_get_try_format(struct v4l2_subdev *sd,
> > > + struct v4l2_subdev_pad_config *cfg,
> > > + unsigned int pad)
> > > +{
> > > + WARN_ON(pad >= sd->entity.num_pads);
> > > + return &cfg[pad].try_fmt;
> > > +}
> > >
> > > -__V4L2_SUBDEV_MK_GET_TRY(v4l2_mbus_framefmt, v4l2_subdev_get_try_format, try_fmt)
> > > -__V4L2_SUBDEV_MK_GET_TRY(v4l2_rect, v4l2_subdev_get_try_crop, try_crop)
> > > -__V4L2_SUBDEV_MK_GET_TRY(v4l2_rect, v4l2_subdev_get_try_compose, try_compose)
> > > +static inline struct v4l2_rect
> > > +*v4l2_subdev_get_try_crop(struct v4l2_subdev *sd,
> > > + struct v4l2_subdev_pad_config *cfg,
> > > + unsigned int pad)
> > > +{
> > > + WARN_ON(pad >= sd->entity.num_pads);
> > > + return &cfg[pad].try_crop;
> > > +}
> > > +
> > > +static inline struct v4l2_rect
> > > +*v4l2_subdev_get_try_compose(struct v4l2_subdev *sd,
> > > + struct v4l2_subdev_pad_config *cfg,
> > > + unsigned int pad)
> > > +{
> > > + WARN_ON(pad >= sd->entity.num_pads);
> > > + return &cfg[pad].try_compose;
> > > +}
> > > #endif
> > >
> > > extern const struct v4l2_file_operations v4l2_subdev_fops;
> >
>
>
>
> Thanks,
> Mauro
--
Sakari Ailus
e-mail: sakari.ailus@xxxxxx
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