Hi Hans, On Tuesday 02 December 2014 13:53:05 Hans Verkuil wrote: > On 12/02/14 08:45, Hans Verkuil wrote: > > On 12/02/2014 12:26 AM, Laurent Pinchart wrote: > >> On Sunday 30 November 2014 21:30:35 Prabhakar Lad wrote: > >>> On Sun, Nov 30, 2014 at 9:16 PM, Laurent Pinchart wrote: > >>>> On Sunday 30 November 2014 21:05:50 Prabhakar Lad wrote: > >>>>> On Sat, Nov 29, 2014 at 7:12 PM, Laurent Pinchart wrote: > >>>>>> Hi Prabhakar, > >>>>> > >>>>> [Snip] > >>>>> > >>>>>>>> Sure. That's a better choice than removing the config option > >>>>>>>> dependency of the fields struct v4l2_subdev. > >>>>>> > >>>>>> Decoupling CONFIG_VIDEO_V4L2_SUBDEV_API from the availability of the > >>>>>> in-kernel pad format and selection rectangles helpers is definitely a > >>>>>> good idea. I was thinking about decoupling the try format and > >>>>>> rectangles from v4l2_subdev_fh by creating a kind of configuration > >>>>>> store structure to store them, and embedding that structure in > >>>>>> v4l2_subdev_fh. The pad-level operations would then take a pointer to > >>>>>> the configuration store instead of the v4l2_subdev_fh. Bridge drivers > >>>>>> that want to implement TRY_FMT based on pad-level operations would > >>>>>> create a configuration store, use the pad-level operations, and > >>>>>> destroy the configuration store. The userspace subdev API would use > >>>>>> the configuration store from the file handle. > >>>>> > >>>>> are planning to work/post any time soon ? Or are you OK with > >>>>> suggestion from Hans ? > >>>> > >>>> I have no plan to work on that myself now, I was hoping you could > >>>> implement it ;-) > >>> > >>> OK will implement it. > >>> > >>> Can you please elaborate a more on this "The userspace subdev API would > >>> use the configuration store from the file handle." > >> > >> Basically, > >> > >> 1. Create a subdev pad configuration store structure to store the formats > >> and selection rectangles for each pad. > > > > I wouldn't call it a 'store'. Just call it fmt_config or pad_config > > something like that. Sure, the name doesn't matter too much. > >> 2. Embed an instance of that structure in v4l2_subdev_fh. > >> > >> 3. Modify the subdev pad ops to take a configuration store pointer > >> instead of a file handle pointer. > >> > >> The userspace API implementation (v4l2-subdev.c) would then pass > >> &fh->store to the pad operations instead of fh. > >> > >> Bridge drivers that need to implement TRY_FMT on top of pad ops would > >> create a temporary store (or temporary stores when multiple subsdevs are > >> involved), call the pad ops with a pointer to the temporary store to > >> propagate TRY formats, destroy the store(s) and return the resulting > >> format. > > > > That will work. I think this is a good approach and it shouldn't be too > > difficult. > > Laurent, just so I understand this correctly: does this mean that all > occurrences of 'struct v4l2_subdev_fh *fh' will be replaced by 'struct > v4l2_subdev_pad_config *cfg'? That's the plan, yes. > Is there any reason why the 'fh' should still be passed on? We might find out reasons to still pass the fh, but in that case I think they should be addressed and the fh just dropped from the pad ops arguments. > Personally I am in favor of this since the 'fh' always made it hard for > bridge drivers to use these pad ops. So if we can replace it by something > that can be used by bridge drivers as well, then that will make it easier > to move all drivers over to the pad ops. Good, looks like we have a plan for world domination :-) -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
