On Tue, Sep 19, 2023 at 06:21:23PM +0300, Laurent Pinchart wrote:
> On Tue, Sep 19, 2023 at 02:49:29PM +0000, Sakari Ailus wrote:
> > Hi Laurent,
> >
> > On Tue, Sep 19, 2023 at 04:32:48PM +0300, Laurent Pinchart wrote:
> > > Hi Sakari,
> > >
> > > Thank you for the patch.
> > >
> > > On Tue, Sep 19, 2023 at 03:17:27PM +0300, Sakari Ailus wrote:
> > > > Print debug level information on returned frame descriptors.
> > > >
> > > > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> > > > ---
> > > > drivers/media/v4l2-core/v4l2-subdev.c | 32 ++++++++++++++++++++++++++-
> > > > 1 file changed, 31 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> > > > index 7b087be3ff4f..504ca625b2bd 100644
> > > > --- a/drivers/media/v4l2-core/v4l2-subdev.c
> > > > +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> > > > @@ -15,6 +15,7 @@
> > > > #include <linux/module.h>
> > > > #include <linux/overflow.h>
> > > > #include <linux/slab.h>
> > > > +#include <linux/string.h>
> > > > #include <linux/types.h>
> > > > #include <linux/version.h>
> > > > #include <linux/videodev2.h>
> > > > @@ -309,9 +310,38 @@ static int call_set_selection(struct v4l2_subdev *sd,
> > > > static int call_get_frame_desc(struct v4l2_subdev *sd, unsigned int pad,
> > > > struct v4l2_mbus_frame_desc *fd)
> > > > {
> > > > + unsigned int i;
> > > > + int ret;
> > > > +
> > > > memset(fd, 0, sizeof(*fd));
> > > >
> > > > - return sd->ops->pad->get_frame_desc(sd, pad, fd);
> > > > + ret = sd->ops->pad->get_frame_desc(sd, pad, fd);
> > > > + if (ret)
> > > > + return ret;
> > > > +
> > > > + dev_dbg(sd->dev, "Frame descriptor on pad %u, type %s\n", pad,
> > > > + fd->type == V4L2_MBUS_FRAME_DESC_TYPE_PARALLEL ? "parallel" :
> > > > + fd->type == V4L2_MBUS_FRAME_DESC_TYPE_CSI2 ? "CSI-2" :
> > > > + "unknown");
> > > > +
> > > > + for (i = 0; i < fd->num_entries; i++) {
> > > > + struct v4l2_mbus_frame_desc_entry *entry = &fd->entry[i];
> > > > + char buf[20] = "";
> > >
> > > Should this be sized for the worst case ? The vc and dt should not be
> > > large, but a buffer overflow on the stack in debug code if a subdev
> > > returns an incorrect value would be bad.
> >
> > 17 should be enough but it's not useful to use a size not divisible by 4 in
> > practice here.
>
> 18 with the terminating 0. But indeed, it's large enough as vc and dt
I can count only 17 --- there's no newline.
I guess it's most probably either of these then. X-)
> are u8. I'm just a bit worried we're opening the door to hard to debug
> problems if we later change the vc and dt types.
I can add a WARN_ON() to cover this.
>
> > > > +
> > > > + if (fd->type == V4L2_MBUS_FRAME_DESC_TYPE_CSI2)
> > > > + snprintf(buf, sizeof(buf), ", vc %u, dt 0x%2.2x",
> > >
> > > 0x%02x would be one character shorter ;-) Same below.
> >
> > It would be, but I prefer the above notation as it's more generic.
>
> Out of curiosity, how so ?
It works with data that would span more than 9 characters when printed.
>
> > > > + entry->bus.csi2.vc, entry->bus.csi2.dt);
> > > > +
> > > > + dev_dbg(sd->dev,
> > > > + "\tstream %u, code 0x%4.4x, lenght %u, flags%s%s%s\n",
> > >
> > > s/lenght/length/
> >
> > Thanks, I'll fix this.
> >
> > > > + entry->stream, entry->pixelcode, entry->length,
> > > > + entry->flags & V4L2_MBUS_FRAME_DESC_FL_LEN_MAX ?
> > > > + " LEN_MAX" : "",
> > > > + entry->flags & V4L2_MBUS_FRAME_DESC_FL_BLOB ?
> > > > + " BLOB" : "", buf);
> > >
> > > If no flags are set, you will get something like
> > >
> > > stream 0, code 0x1234, length ..., flags, vc 0, dt 0x2a
> > >
> > > Maybe printing the hex value for the flags would be simpler and clearer
> > > ?
> >
> > How about adding the numerical value in addition to the strings?
> >
> > The use of these flags is rare though. I could just remove the strings,
> > too.
>
> Up to you.
On second thought, I'll make it an integer only. If we'll get more commonly
used flags, we can rethink about strings.
--
Regards,
Sakari Ailus
