Re: [PATCH v3 17/33] v4l: Implement v4l2_subdev_link_validate()

Sakari Ailus
2012-02-24T11:50:36Z

Hi Laurent,

Laurent Pinchart wrote:
> Hi Sakari,
>
> Thanks for the patch.

Thanks for your comments!!

> On Monday 20 February 2012 03:56:56 Sakari Ailus wrote:
>> v4l2_subdev_link_validate() is the default op for validating a link. In V4L2
>> subdev context, it is used to call a pad op which performs the proper link
>> check without much extra work.
>>
>> Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
>> ---
>> Documentation/video4linux/v4l2-framework.txt | 12 +++++
>> drivers/media/video/v4l2-subdev.c | 69
>> ++++++++++++++++++++++++++ include/media/v4l2-subdev.h |
>> 12 +++++
>> 3 files changed, 93 insertions(+), 0 deletions(-)
>>
>> diff --git a/Documentation/video4linux/v4l2-framework.txt
>> b/Documentation/video4linux/v4l2-framework.txt index f06c563..9d341bc
>> 100644
>> --- a/Documentation/video4linux/v4l2-framework.txt
>> +++ b/Documentation/video4linux/v4l2-framework.txt
>> @@ -312,6 +312,18 @@ If the subdev driver intends to process video and
>> integrate with the media framework, it must implement format related
>> functionality using
>> v4l2_subdev_pad_ops instead of v4l2_subdev_video_ops.
>>
>> +In that case, the subdev driver may set the link_validate field to provide
>> +its own link validation function. The link validation function is called
>> for +every link in the pipeline where both of the ends of the links are
>> V4L2 +sub-devices. The driver is still responsible for validating the
>> correctness +of the format configuration between sub-devices and video
>> nodes.
>> +
>> +If link_validate op is not set, the default function
>> +v4l2_subdev_link_validate_default() is used instead. This function ensures
>> +that width, height and the media bus pixel code are equal on both source
>> and +sink of the link. Subdev drivers are also free to use this function to
>> +perform the checks mentioned above in addition to their own checks. +
>> A device (bridge) driver needs to register the v4l2_subdev with the
>> v4l2_device:
>>
>> diff --git a/drivers/media/video/v4l2-subdev.c
>> b/drivers/media/video/v4l2-subdev.c index ef27144..d2ec552 100644
>> --- a/drivers/media/video/v4l2-subdev.c
>> +++ b/drivers/media/video/v4l2-subdev.c
>> @@ -379,6 +379,75 @@ const struct v4l2_file_operations v4l2_subdev_fops = {
>> .poll = subdev_poll,
>> };
>>
>> +#ifdef CONFIG_MEDIA_CONTROLLER
>> +int v4l2_subdev_link_validate_default(struct v4l2_subdev *sd,
>> + struct media_link *link,
>> + struct v4l2_subdev_format *source_fmt,
>> + struct v4l2_subdev_format *sink_fmt)
>> +{
>> + if (source_fmt->format.width != sink_fmt->format.width
>> + || source_fmt->format.height != sink_fmt->format.height
>> + || source_fmt->format.code != sink_fmt->format.code)
>> + return -EINVAL;
>> +
>> + return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(v4l2_subdev_link_validate_default);
>> +
>> +static struct v4l2_subdev_format
>> +*v4l2_subdev_link_validate_get_format(struct media_pad *pad,
>> + struct v4l2_subdev_format *fmt)
>
> Why do you return a pointer to the passed struct v4l2_subdev_format instead of
> just an error code ?

I don't remember. ;-) I'll replace that with an integer return value for
the next version.

>> +{
>> + int rval;
>
> I would have used ret instead of rval as that's the preferred variable name in
> this file (OK, I'm cheating, there's a single instance of ret, and I wrote
> that one ;-)).

If you can get a patch through to Documentation/CodingStyle that
recognises "ret" as the variable name for return value, I'll change it.
How about that? ;-) ;-)

>> +
>> + switch (media_entity_type(pad->entity)) {
>> + case MEDIA_ENT_T_V4L2_SUBDEV:
>> + fmt->which = V4L2_SUBDEV_FORMAT_ACTIVE;
>> + fmt->pad = pad->index;
>> + rval = v4l2_subdev_call(media_entity_to_v4l2_subdev(
>> + pad->entity),
>> + pad, get_fmt, NULL, fmt);
>> + if (rval < 0)
>> + return NULL;
>> + return fmt;
>> + default:
>> + WARN(1, "Driver bug! Wrong media entity type %d, entity %s\n",
>> + media_entity_type(pad->entity), pad->entity->name);
>> + /* Fall through */
>> + case MEDIA_ENT_T_DEVNODE_V4L:
>> + return NULL;
>> + }
>> +}
>> +
>> +int v4l2_subdev_link_validate(struct media_link *link)
>> +{
>> + struct v4l2_subdev *sink;
>> + struct v4l2_subdev_format _sink_fmt, _source_fmt;
>> + struct v4l2_subdev_format *sink_fmt, *source_fmt;
>> + int rval;
>> +
>> + source_fmt = v4l2_subdev_link_validate_get_format(
>> + link->source, &_source_fmt);
>> + if (!source_fmt)
>> + return 0;
>> +
>> + sink_fmt = v4l2_subdev_link_validate_get_format(
>> + link->sink, &_sink_fmt);
>> + if (!sink_fmt)
>> + return 0;
>> +
>> + sink = media_entity_to_v4l2_subdev(link->sink->entity);
>> +
>> + rval = v4l2_subdev_call(sink, pad, link_validate, link,
>> + source_fmt, sink_fmt);
>> + if (rval < 0 && rval != -ENOIOCTLCMD)
>> + return rval;
>> + return v4l2_subdev_link_validate_default(sink, link, source_fmt,
>> + sink_fmt);
>
> I don't think you should call v4l2_subdev_link_validate_default() if the
> link_validate operation is implemented and returns that the link is valid. The
> subdev might have weaker requirements than the default.

Right; the link validation should succeed by default. I'll remove that part.

>> +}
>> +EXPORT_SYMBOL_GPL(v4l2_subdev_link_validate);
>> +#endif /* CONFIG_MEDIA_CONTROLLER */
>> +
>> void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops
>> *ops) {
>> INIT_LIST_HEAD(&sd->list);
>> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
>> index d48dae5..f115608 100644
>> --- a/include/media/v4l2-subdev.h
>> +++ b/include/media/v4l2-subdev.h
>> @@ -470,6 +470,11 @@ struct v4l2_subdev_pad_ops {
>> struct v4l2_subdev_selection *sel);
>> int (*set_selection)(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh,
>> struct v4l2_subdev_selection *sel);
>> +#ifdef CONFIG_MEDIA_CONTROLLER
>> + int (*link_validate)(struct v4l2_subdev *sd, struct media_link *link,
>> + struct v4l2_subdev_format *source_fmt,
>> + struct v4l2_subdev_format *sink_fmt);
>> +#endif /* CONFIG_MEDIA_CONTROLLER */
>> };
>>
>> struct v4l2_subdev_ops {
>> @@ -603,6 +608,13 @@ static inline void *v4l2_get_subdev_hostdata(const
>> struct v4l2_subdev *sd) return sd->host_priv;
>> }
>>
>> +#ifdef CONFIG_MEDIA_CONTROLLER
>> +int v4l2_subdev_link_validate_default(struct v4l2_subdev *sd,
>> + struct media_link *link,
>> + struct v4l2_subdev_format *source_fmt,
>> + struct v4l2_subdev_format *sink_fmt);
>> +int v4l2_subdev_link_validate(struct media_link *link);
>> +#endif /* CONFIG_MEDIA_CONTROLLER */
>> void v4l2_subdev_init(struct v4l2_subdev *sd,
>> const struct v4l2_subdev_ops *ops);

--
Sakari Ailus
sakari.ailus@iki.fi