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From: Sakari Ailus <sakari.ailus@linux.intel.com>
To: Jacopo Mondi <jacopo@jmondi.org>
Cc: "Laurent Pinchart" <laurent.pinchart@ideasonboard.com>,
	"Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>,
	"Benoit Parrot" <bparrot@ti.com>,
	linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
	"Michal Simek" <michal.simek@xilinx.com>
Subject: Re: [PATCH v2 16/30] v4l: subdev: Add [GS]_ROUTING subdev ioctls and operations
Date: Fri, 22 Feb 2019 01:49:36 +0200
Message-ID: <20190221234936.pbbymgzmqrv7ypje@kekkonen.localdomain> (raw)
In-Reply-To: <20190221145920.7w7mynzhdwln4drb@uno.localdomain>

Hi Jacopo,

On Thu, Feb 21, 2019 at 03:59:20PM +0100, Jacopo Mondi wrote:
> Hi Sakari, Laurent, Niklas,
>    (another) quick question, but a different one :)
> 
> On Wed, Jan 16, 2019 at 01:51:45AM +0200, Laurent Pinchart wrote:
> > Hi Niklas,
> >
> > Thank you for the patch.
> >
> > On Fri, Nov 02, 2018 at 12:31:30AM +0100, Niklas Söderlund wrote:
> > > From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > >
> > > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > Signed-off-by: Michal Simek <michal.simek@xilinx.com>
> > >
> > > - 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@linux.intel.com>
> > > Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> > > ---
> > >  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 +++++++++++++++++++++++++++
> >
> > Missing documentation :-(
> >
> > >  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)
> >
> > This seems like a hack. Shouldn't VIDIOC_SUBDEV_G_ROUTING set
> > always_copy instead ?
> >
> > >  		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;
> > > +
> > > +		for (i = 0; i < route->num_routes; ++i) {
> 
> How have you envisioned the number of routes to be negotiated with
> applications? I'm writing the documentation for this ioctl, and I
> would like to insert this part as well.
> 
> Would a model like the one implemented in G_TOPOLOGY work in your
> opinion? In my understanding, at the moment applications do not have a
> way to reserve a known number of routes entries, but would likely
> reserve 'enough(tm)' (ie 256) and pass them to the G_ROUTING ioctl that the
> first time will likely adjust the number of num_routes and return -ENOSPC.
> 
> Wouldn't it work to make the IOCTL behave in a way that it
> expects the first call to be performed with (num_routes == 0) and no routes
> entries reserved, and just adjust 'num_routes' in that case?
> So that applications should call G_ROUTING a first time with
> num_routes = 0, get back the number of routes entries, reserve memory
> for them, and then call G_ROUTING again to have the entries populated
> by the driver. Do you have different ideas or was this the intended
> behavior already?

I think whenever the number of routes isn't enough to return them all, the
IOCTL should return -ENOSPC, and set the actual number of routes there. Not
just zero. The user could e.g. try with a static allocation of some, and
allocate memory if the static allocation turns not to be enough.

Btw. the idea behind S_ROUTING behaviour was to allow multiple users to
work on a single sub-device without having to know about each other. That's
why there are flags to tell which routes are enabled and which are not.

I'll be better available tomorrow, let's discuss e.g. on #v4l then.

-- 
Sakari Ailus
sakari.ailus@linux.intel.com

  reply index

Thread overview: 90+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-01 23:31 [PATCH v2 00/30] v4l: add support for multiplexed streams Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 01/30] media: entity: Use pad as a starting point for graph walk Niklas Söderlund
2019-01-15 21:43   ` Laurent Pinchart
2018-11-01 23:31 ` [PATCH v2 02/30] media: entity: Use pads instead of entities in the media graph walk stack Niklas Söderlund
2019-01-15 22:03   ` Laurent Pinchart
2019-01-15 22:13     ` Sakari Ailus
2019-01-15 22:07   ` Laurent Pinchart
2018-11-01 23:31 ` [PATCH v2 03/30] media: entity: Walk the graph based on pads Niklas Söderlund
2019-01-15 22:21   ` Laurent Pinchart
     [not found]     ` <20190115223406.mxgzl36cp54gb7nv@kekkonen.localdomain>
2019-01-15 23:28       ` Laurent Pinchart
2019-01-22 14:50         ` Sakari Ailus
2019-02-14 15:15   ` Jacopo Mondi
2018-11-01 23:31 ` [PATCH v2 04/30] v4l: mc: Start walk from a specific pad in use count calculation Niklas Söderlund
2019-01-15 22:24   ` Laurent Pinchart
2019-01-15 22:36     ` Sakari Ailus
2018-11-01 23:31 ` [PATCH v2 05/30] media: entity: Move the pipeline from entity to pads Niklas Söderlund
2019-01-15 22:38   ` Laurent Pinchart
2019-01-15 22:48     ` Sakari Ailus
2019-02-14 15:53   ` Jacopo Mondi
2018-11-01 23:31 ` [PATCH v2 06/30] media: entity: Use pad as the starting point for a pipeline Niklas Söderlund
2019-01-15 22:54   ` Laurent Pinchart
2019-01-22 15:31     ` Sakari Ailus
2019-01-22 15:37       ` Laurent Pinchart
2019-01-22 16:16         ` Sakari Ailus
2018-11-01 23:31 ` [PATCH v2 07/30] media: entity: Add has_route entity operation Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 08/30] media: entity: Add media_has_route() function Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 09/30] media: entity: Swap pads if route is checked from source to sink Niklas Söderlund
2019-01-15 22:57   ` Laurent Pinchart
2019-01-22 15:15     ` Sakari Ailus
2019-01-22 15:20       ` Laurent Pinchart
2019-02-18  9:21         ` Jacopo Mondi
2019-02-22 12:18           ` Laurent Pinchart
2019-03-04 12:35             ` Jacopo Mondi
2019-03-05 20:04               ` Laurent Pinchart
2019-03-06  8:29                 ` Jacopo Mondi
2018-11-01 23:31 ` [PATCH v2 10/30] media: entity: Use routing information during graph traversal Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 11/30] media: entity: Skip link validation for pads to which there is no route to Niklas Söderlund
2019-01-15 23:13   ` Laurent Pinchart
2018-11-01 23:31 ` [PATCH v2 12/30] media: entity: Add an iterator helper for connected pads Niklas Söderlund
2019-01-15 23:24   ` Laurent Pinchart
2019-01-22 15:36     ` Sakari Ailus
2019-01-22 15:38       ` Laurent Pinchart
2019-01-22 16:21         ` Sakari Ailus
2018-11-01 23:31 ` [PATCH v2 13/30] media: entity: Add only connected pads to the pipeline Niklas Söderlund
2019-01-15 23:33   ` Laurent Pinchart
2018-11-01 23:31 ` [PATCH v2 14/30] media: entity: Add debug information in graph walk route check Niklas Söderlund
2019-01-15 23:35   ` Laurent Pinchart
2019-01-22 15:38     ` Sakari Ailus
2018-11-01 23:31 ` [PATCH v2 15/30] media: entity: Look for indirect routes Niklas Söderlund
2019-01-15 23:41   ` Laurent Pinchart
2019-01-22 15:56     ` Sakari Ailus
2018-11-01 23:31 ` [PATCH v2 16/30] v4l: subdev: Add [GS]_ROUTING subdev ioctls and operations Niklas Söderlund
2019-01-15 23:51   ` Laurent Pinchart
2019-01-22 16:14     ` Sakari Ailus
2019-01-22 17:00       ` Laurent Pinchart
2019-02-21 14:59     ` Jacopo Mondi
2019-02-21 23:49       ` Sakari Ailus [this message]
2019-02-22  8:46         ` Jacopo Mondi
2019-02-21 14:39   ` Jacopo Mondi
2019-02-21 22:31     ` Sakari Ailus
2019-02-22  8:40       ` Jacopo Mondi
2019-02-22 11:04         ` Sakari Ailus
2019-02-22 11:17           ` Jacopo Mondi
2019-02-22 11:29             ` Sakari Ailus
2019-02-22 13:37               ` Ian Arkver
2019-02-22 13:50               ` Geert Uytterhoeven
2018-11-01 23:31 ` [PATCH v2 17/30] v4l: subdev: compat: Implement handling for VIDIOC_SUBDEV_[GS]_ROUTING Niklas Söderlund
2019-01-08 10:04   ` Geert Uytterhoeven
2019-01-15 23:53   ` Laurent Pinchart
2019-01-22 15:57     ` Sakari Ailus
2019-02-18 11:21     ` Jacopo Mondi
2019-02-21 23:50       ` Sakari Ailus
2018-11-01 23:31 ` [PATCH v2 18/30] v4l: subdev: Take routing information into account in link validation Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 19/30] v4l: subdev: Improve link format validation debug messages Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 20/30] v4l: mc: Add an S_ROUTING helper function for power state changes Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 21/30] v4l: Add bus type to frame descriptors Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 22/30] v4l: Add CSI-2 bus configuration " Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 23/30] v4l: Add stream to frame descriptor Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 24/30] adv748x: csi2: add translation from pixelcode to CSI-2 datatype Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 25/30] adv748x: csi2: only allow formats on sink pads Niklas Söderlund
2019-02-21 14:18   ` Jacopo Mondi
2018-11-01 23:31 ` [PATCH v2 26/30] adv748x: csi2: describe the multiplexed stream Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 27/30] adv748x: csi2: add internal routing configuration Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 28/30] adv748x: afe: add routing support Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 29/30] rcar-csi2: use frame description information to configure CSI-2 bus Niklas Söderlund
2018-11-01 23:31 ` [PATCH v2 30/30] rcar-csi2: expose the subdevice internal routing Niklas Söderlund
2018-11-14 13:10   ` Nikita Yushchenko
2018-11-14 19:45     ` Niklas Söderlund
2018-12-03 22:16 ` [PATCH v2 00/30] v4l: add support for multiplexed streams Sakari Ailus
2018-12-05 22:09   ` Niklas Söderlund

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