Re: [RFCv1 PATCH 0/4] add G/S_EDID support for video nodes

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Hans,

On Thursday 06 March 2014 08:35:07 Hans Verkuil wrote:
> On 03/06/2014 02:45 AM, Laurent Pinchart wrote:
> > On Tuesday 04 March 2014 12:30:55 Hans Verkuil wrote:
> >> Currently the VIDIOC_SUBDEV_G/S_EDID and struct v4l2_subdev_edid are
> >> subdev APIs. However, that's in reality quite annoying since for simple
> >> video pipelines there is no need to create v4l-subdev device nodes for
> >> anything else except for setting or getting EDIDs.
> >> 
> >> What happens in practice is that v4l2 bridge drivers add explicit support
> >> for VIDIOC_SUBDEV_G/S_EDID themselves, just to avoid having to create
> >> subdev device nodes just for this.
> >> 
> >> So this patch series makes the ioctls available as regular ioctls as
> >> well. In that case the pad field should be set to 0 and the bridge driver
> >> will fill in the right pad value internally depending on the current
> >> input or output and pass it along to the actual subdev driver.
> > 
> > Would it make sense to allow usage of the pad field on video nodes as well
> > ?
> No, really not. The video node driver has full control over which
> inputs/outputs map to which pads. None of that is (or should be) visible
> from userspace.

What about using the pad field as an input number in that case ? That would 
allow getting and setting EDID for the different inputs without requiring to 
change the active input, just like we can do with the subdev API.

> What should probably change is that rather than requiring userspace to set
> pad to 0, I just say that it is ignored. The bridge driver will fill in the
> pad before handing it over to the relevant subdev. Requiring apps to set it
> to 0 (which is a valid pad number anyway, so that doesn't really help with
> possible future use of the field) will require the driver to set it to 0 as
> well after having called the subdev. Which is annoying and will be
> forgotten anyway.
> 
> I also need to mention in the docbook that if it is called for a pad, an
> input or an output that does not support EDIDs these ioctls will return
> -EINVAL.
> 
> I'll post a REVIEWv1 series soon.
> 
> Regards,
> 
> 	Hans
> 
> > Apart from that and minor issues with patch 2/4 this series looks good to
> > me.

-- 
Regards,

Laurent Pinchart