On Mon, Nov 25, 2024 at 10:34:40PM +0200, Cosmin Tanislav wrote:
> On 11/23/24 11:32 PM, Laurent Pinchart wrote:
> > On Fri, Nov 22, 2024 at 05:33:39PM +0200, Cosmin Tanislav wrote:
> >> The error values end up being returned to userspace, it makes sense to
> >> have some useful information printed when debugging them, even if the
> >> reason for the errors are bad configs or internal driver issues.
> >>
> >> Replace dev_dbg() with dev_err() for errors.
> >
> > We use dev_dbg() on purpose for all errors that can be triggered
> > directly by applications. This includes in particular all pipeline
> > validation errors.
> >
> > The error paths in this specific patch shouldn't be in that category, as
> > all the validation should have been performed before starting subdevs
> > (assuming all drivers are correctly implemented, which is of course not
> > a given, but those issues should be fixed). I think we could therefore
> > switch to dev_err() here. However, I'm wondering what kind of issues
> > triggered this patch. What errors did you run into that would have
> > benefited from being reported more loudly, and were they caused by
> > driver bugs or userspace misconfiguring the device ?
>
> I've had this patch in my GMSL2 tree for some time now, I believe indeed
> the reasons why I've hit these error cases were the drivers being
> slightly broken, but I still think it is worthwhile to show an error
> message, to aid with debugging. Adding the entity name to the messages
> makes it even more clear where exactly the code is breaking.
>
> I can split it up into separate patches for dev_dbg() -> dev_err() and
> adding the entity name to the print statements for V2.
I'm OK either way. If other people prefer keeping dev_dbg() then
splitting the patch in two would make sense.
> >> Also, when using complex pipelines with multiple bridges between the
> >> video device and multiple source sub devices, printing just the video
> >> device name for each error does not provide enough context as to which
> >> operation failed.
> >>
> >> Add sub device entity name to the messages where possible to clarify the
> >> source of the errors.
> >
> > This can be considered as a standalone patch.
> >
> >> Signed-off-by: Cosmin Tanislav <demonsingur@xxxxxxxxx>
> >> ---
> >> drivers/media/v4l2-core/v4l2-subdev.c | 22 ++++++++++++----------
> >> 1 file changed, 12 insertions(+), 10 deletions(-)
> >>
> >> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> >> index 4f0eecd7fd66f..d51b4594d11c5 100644
> >> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> >> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> >> @@ -2303,20 +2303,21 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
> >> &found_streams, &enabled_streams);
> >>
> >> if (found_streams != streams_mask) {
> >> - dev_dbg(dev, "streams 0x%llx not found on %s:%u\n",
> >> + dev_err(dev, "streams 0x%llx not found on %s:%u\n",
> >> streams_mask & ~found_streams, sd->entity.name, pad);
> >> ret = -EINVAL;
> >> goto done;
> >> }
> >>
> >> if (enabled_streams) {
> >> - dev_dbg(dev, "streams 0x%llx already enabled on %s:%u\n",
> >> + dev_err(dev, "streams 0x%llx already enabled on %s:%u\n",
> >> enabled_streams, sd->entity.name, pad);
> >> ret = -EALREADY;
> >> goto done;
> >> }
> >>
> >> - dev_dbg(dev, "enable streams %u:%#llx\n", pad, streams_mask);
> >> + dev_dbg(dev, "enable streams %s:%u:%#llx\n",
> >> + sd->entity.name, pad, streams_mask);
> >>
> >> already_streaming = v4l2_subdev_is_streaming(sd);
> >>
> >> @@ -2333,8 +2334,8 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
> >> }
> >>
> >> if (ret) {
> >> - dev_dbg(dev, "enable streams %u:%#llx failed: %d\n", pad,
> >> - streams_mask, ret);
> >> + dev_err(dev, "enable streams %s:%u:%#llx failed: %d\n",
> >> + sd->entity.name, pad, streams_mask, ret);
> >> goto done;
> >> }
> >>
> >> @@ -2403,20 +2404,21 @@ int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
> >> &found_streams, &enabled_streams);
> >>
> >> if (found_streams != streams_mask) {
> >> - dev_dbg(dev, "streams 0x%llx not found on %s:%u\n",
> >> + dev_err(dev, "streams 0x%llx not found on %s:%u\n",
> >> streams_mask & ~found_streams, sd->entity.name, pad);
> >> ret = -EINVAL;
> >> goto done;
> >> }
> >>
> >> if (enabled_streams != streams_mask) {
> >> - dev_dbg(dev, "streams 0x%llx already disabled on %s:%u\n",
> >> + dev_err(dev, "streams 0x%llx already disabled on %s:%u\n",
> >> streams_mask & ~enabled_streams, sd->entity.name, pad);
> >> ret = -EALREADY;
> >> goto done;
> >> }
> >>
> >> - dev_dbg(dev, "disable streams %u:%#llx\n", pad, streams_mask);
> >> + dev_dbg(dev, "disable streams %s:%u:%#llx\n",
> >> + sd->entity.name, pad, streams_mask);
> >>
> >> if (!use_s_stream) {
> >> /* Call the .disable_streams() operation. */
> >> @@ -2432,8 +2434,8 @@ int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
> >> }
> >>
> >> if (ret) {
> >> - dev_dbg(dev, "disable streams %u:%#llx failed: %d\n", pad,
> >> - streams_mask, ret);
> >> + dev_err(dev, "disable streams %s:%u:%#llx failed: %d\n",
> >> + sd->entity.name, pad, streams_mask, ret);
> >> goto done;
> >> }
> >>
--
Regards,
Laurent Pinchart
