Hi Jacopo,
On Fri, Feb 22, 2019 at 09:40:19AM +0100, Jacopo Mondi wrote:
> Hi Sakari,
>
> On Fri, Feb 22, 2019 at 12:31:32AM +0200, Sakari Ailus wrote:
> > Hi Jacopo,
> >
> > On Thu, Feb 21, 2019 at 03:39:40PM +0100, Jacopo Mondi wrote:
> > > Hi Sakari,
> > > one quick question
> > >
> > > On Fri, Nov 02, 2018 at 12:31:30AM +0100, Niklas Söderlund wrote:
> > > > From: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > > >
> > > > Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > > > Signed-off-by: Michal Simek <michal.simek@xxxxxxxxxx>
> > > >
> > > > - Add sink and source streams for multiplexed links
> > > > - Copy the argument back in case of an error. This is needed to let the
> > > > caller know the number of routes.
> > > >
> > > > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> > > > Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
> > > > ---
> > > > drivers/media/v4l2-core/v4l2-ioctl.c | 20 +++++++++++++-
> > > > drivers/media/v4l2-core/v4l2-subdev.c | 28 +++++++++++++++++++
> > > > include/media/v4l2-subdev.h | 7 +++++
> > > > include/uapi/linux/v4l2-subdev.h | 40 +++++++++++++++++++++++++++
> > > > 4 files changed, 94 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> > > > index 7de041bae84fb2f2..40406acb51ec0906 100644
> > > > --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> > > > +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> > > > @@ -19,6 +19,7 @@
> > > > #include <linux/kernel.h>
> > > > #include <linux/version.h>
> > > >
> > > > +#include <linux/v4l2-subdev.h>
> > > > #include <linux/videodev2.h>
> > > >
> > > > #include <media/v4l2-common.h>
> > > > @@ -2924,6 +2925,23 @@ static int check_array_args(unsigned int cmd, void *parg, size_t *array_size,
> > > > }
> > > > break;
> > > > }
> > > > +
> > > > + case VIDIOC_SUBDEV_G_ROUTING:
> > > > + case VIDIOC_SUBDEV_S_ROUTING: {
> > > > + struct v4l2_subdev_routing *route = parg;
> > > > +
> > > > + if (route->num_routes > 0) {
> > > > + if (route->num_routes > 256)
> > > > + return -EINVAL;
> > > > +
> > > > + *user_ptr = (void __user *)route->routes;
> > > > + *kernel_ptr = (void *)&route->routes;
> > > > + *array_size = sizeof(struct v4l2_subdev_route)
> > > > + * route->num_routes;
> > > > + ret = 1;
> > > > + }
> > > > + break;
> > > > + }
> > > > }
> > > >
> > > > return ret;
> > > > @@ -3033,7 +3051,7 @@ video_usercopy(struct file *file, unsigned int cmd, unsigned long arg,
> > > > * Some ioctls can return an error, but still have valid
> > > > * results that must be returned.
> > > > */
> > > > - if (err < 0 && !always_copy)
> > > > + if (err < 0 && !always_copy && cmd != VIDIOC_SUBDEV_G_ROUTING)
> > > > goto out;
> > > >
> > > > out_array_args:
> > > > diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> > > > index 792f41dffe2329b9..1d3b37cf548fa533 100644
> > > > --- a/drivers/media/v4l2-core/v4l2-subdev.c
> > > > +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> > > > @@ -516,7 +516,35 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
> > > >
> > > > case VIDIOC_SUBDEV_QUERYSTD:
> > > > return v4l2_subdev_call(sd, video, querystd, arg);
> > > > +
> > > > + case VIDIOC_SUBDEV_G_ROUTING:
> > > > + return v4l2_subdev_call(sd, pad, get_routing, arg);
> > > > +
> > > > + case VIDIOC_SUBDEV_S_ROUTING: {
> > > > + struct v4l2_subdev_routing *route = arg;
> > > > + unsigned int i;
> > > > +
> > > > + if (route->num_routes > sd->entity.num_pads)
> > > > + return -EINVAL;
> > >
> > > Can't the number of routes exceeds the total number of pad?
> > >
> > > To make an example, a subdevice with 2 sink pads, and 1 multiplexed
> > > source pad, with 2 streams would expose the following routing table,
> > > right?
> > >
> > > pad #0 = sink, 1 stream
> > > pad #1 = sink, 1 stream
> > > pad #2 = source, 2 streams
> > >
> > > Routing table:
> > > 0/0 -> 2/0
> > > 0/0 -> 2/1
> > > 1/0 -> 2/0
> > > 1/0 -> 2/1
> > >
> > > In general, the number of accepted routes should depend on the number
> > > of streams, not pads, and that's better handled by drivers, am I
> > > wrong?
> >
> > Good point. Is the above configuration meaningful? I.e. you have a mux
> > device that does some processing as well by combining the streams?
> >
> > It's far-fetched but at the moment the API does not really bend for that.
> > It still might in the future.
>
> Well, how would you expect a routing table for a device that
> supports multiplexing using Virtual Channels to look like?
>
> As far as I got it, even with a single sink and a single source, it
> would be:
>
> [SINK/SINK_STREAM -> SOURCE/SOURCE_STREAM]
> 0/0 -> 1/0
> 0/0 -> 1/1
> 0/0 -> 1/2
> 0/0 -> 1/3
>
> On the previous example, I thought about GMSL-like devices, that can
> output the video streams received from different remotes in a
> separate virtual channel, at the same time.
>
> A possible routing table in that case would be like:
>
> Pads 0, 1, 2, 3 = SINKS
> Pad 4 = SOURCE with 4 streams (1 for each VC)
>
> 0/0 -> 4/0
> 0/0 -> 4/1
> 0/0 -> 4/2
> 0/0 -> 4/3
> 1/0 -> 4/0
> 1/0 -> 4/1
> 1/0 -> 4/2
> 1/0 -> 4/3
> 2/0 -> 4/0
> 2/0 -> 4/1
> 2/0 -> 4/2
> 2/0 -> 4/3
> 3/0 -> 4/0
> 3/0 -> 4/1
> 3/0 -> 4/2
> 3/0 -> 4/3
If more than one pad can handle multiplexed streams, then you may end up in
a situation like that. Indeed.
>
> With only one route per virtual channel active at a time.
>
> Does this match your idea?
>
> >
> > I guess we could just remove the check, and let drivers handle it.
> >
>
> Yup, I agree!
>
> > >
> > > Thanks
> > > j
> > >
> > > > +
> > > > + for (i = 0; i < route->num_routes; ++i) {
> > > > + unsigned int sink = route->routes[i].sink_pad;
> > > > + unsigned int source = route->routes[i].source_pad;
> > > > + struct media_pad *pads = sd->entity.pads;
> > > > +
> > > > + if (sink >= sd->entity.num_pads ||
> > > > + source >= sd->entity.num_pads)
> > > > + return -EINVAL;
> > > > +
> > > > + if (!(pads[sink].flags & MEDIA_PAD_FL_SINK) ||
> > > > + !(pads[source].flags & MEDIA_PAD_FL_SOURCE))
> > > > + return -EINVAL;
> > > > + }
> > > > +
> > > > + return v4l2_subdev_call(sd, pad, set_routing, route);
> > > > + }
> > > > #endif
> > > > +
> > > > default:
> > > > return v4l2_subdev_call(sd, core, ioctl, cmd, arg);
> > > > }
> > > > diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> > > > index 9102d6ca566e01f2..5acaeeb9b3cacefa 100644
> > > > --- a/include/media/v4l2-subdev.h
> > > > +++ b/include/media/v4l2-subdev.h
> > > > @@ -679,6 +679,9 @@ struct v4l2_subdev_pad_config {
> > > > *
> > > > * @set_frame_desc: set the low level media bus frame parameters, @fd array
> > > > * may be adjusted by the subdev driver to device capabilities.
> > > > + *
> > > > + * @get_routing: callback for VIDIOC_SUBDEV_G_ROUTING IOCTL handler.
> > > > + * @set_routing: callback for VIDIOC_SUBDEV_S_ROUTING IOCTL handler.
> > > > */
> > > > struct v4l2_subdev_pad_ops {
> > > > int (*init_cfg)(struct v4l2_subdev *sd,
> > > > @@ -719,6 +722,10 @@ struct v4l2_subdev_pad_ops {
> > > > struct v4l2_mbus_frame_desc *fd);
> > > > int (*set_frame_desc)(struct v4l2_subdev *sd, unsigned int pad,
> > > > struct v4l2_mbus_frame_desc *fd);
> > > > + int (*get_routing)(struct v4l2_subdev *sd,
> > > > + struct v4l2_subdev_routing *route);
> > > > + int (*set_routing)(struct v4l2_subdev *sd,
> > > > + struct v4l2_subdev_routing *route);
> > > > };
> > > >
> > > > /**
> > > > diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
> > > > index 03970ce3074193e6..af069bfb10ca23a5 100644
> > > > --- a/include/uapi/linux/v4l2-subdev.h
> > > > +++ b/include/uapi/linux/v4l2-subdev.h
> > > > @@ -155,6 +155,44 @@ struct v4l2_subdev_selection {
> > > > __u32 reserved[8];
> > > > };
> > > >
> > > > +#define V4L2_SUBDEV_ROUTE_FL_ACTIVE (1 << 0)
> > > > +#define V4L2_SUBDEV_ROUTE_FL_IMMUTABLE (1 << 1)
> > > > +
> > > > +/**
> > > > + * struct v4l2_subdev_route - A signal route inside a subdev
> > > > + * @sink_pad: the sink pad
> > > > + * @sink_stream: the sink stream
> > > > + * @source_pad: the source pad
> > > > + * @source_stream: the source stream
> > > > + * @flags: route flags:
> > > > + *
> > > > + * V4L2_SUBDEV_ROUTE_FL_ACTIVE: Is the stream in use or not? An
> > > > + * active stream will start when streaming is enabled on a video
> > > > + * node. Set by the user.
> > > > + *
> > > > + * V4L2_SUBDEV_ROUTE_FL_IMMUTABLE: Is the stream immutable, i.e.
> > > > + * can it be activated and inactivated? Set by the driver.
> > > > + */
> > > > +struct v4l2_subdev_route {
> > > > + __u32 sink_pad;
> > > > + __u32 sink_stream;
> > > > + __u32 source_pad;
> > > > + __u32 source_stream;
> > > > + __u32 flags;
> > > > + __u32 reserved[5];
> > > > +};
> > > > +
> > > > +/**
> > > > + * struct v4l2_subdev_routing - Routing information
> > > > + * @routes: the routes array
> > > > + * @num_routes: the total number of routes in the routes array
> > > > + */
> > > > +struct v4l2_subdev_routing {
> > > > + struct v4l2_subdev_route *routes;
> >
> > This should be just __u64, to avoid writing compat code. The patch was
> > written before we started doing that. :-) Please see e.g. the media device
> > topology IOCTL.
> >
>
> Thanks, I had a look at the MEDIA_ ioctls yesterday, G_TOPOLOGY in
> particular, which uses several pointers to arrays.
>
> Unfortunately, I didn't come up with anything better than using a
> translation structure, from the IOCTL layer to the subdevice
> operations layer:
> https://paste.debian.net/hidden/b192969d/
> (sharing a link for early comments, I can send v3 and you can comment
> there directly if you prefer to :)
Hmm. That is a downside indeed. It's still a lesser problem than the compat
code in general --- which has been a source for bugs as well as nasty
security problems over time.
I think we need a naming scheme for such structs. How about just
calling that struct e.g. v4l2_subdev_krouting instead? It's simple, easy to
understand and it includes a suggestion which one is the kernel-only
variant.
You can btw. zero the struct memory by assigning { 0 } to it in
declaration. memset() in general is much more trouble. In this case you
could even do the assignments in delaration as well.
There is a check that requires that one pad is a source and another is a
sink; I think we could remove that check as well.
--
Regards,
Sakari Ailus
sakari.ailus@xxxxxxxxxxxxxxx
