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From: Sakari Ailus <sakari.ailus@linux.intel.com>
To: Jacopo Mondi <jacopo@jmondi.org>
Cc: "Niklas Söderlund" <niklas.soderlund+renesas@ragnatech.se>,
	"Laurent Pinchart" <laurent.pinchart@ideasonboard.com>,
	"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 13:29:18 +0200
Message-ID: <20190222112917.l7sgmdb56jmbnos2@paasikivi.fi.intel.com> (raw)
In-Reply-To: <20190222111747.tlj2xdjhnjwrlqxx@uno.localdomain>

Hi Jacopo,

On Fri, Feb 22, 2019 at 12:17:47PM +0100, Jacopo Mondi wrote:
> Hi Sakari,
>     thanks for your suggestions.
> 
> On Fri, Feb 22, 2019 at 01:04:29PM +0200, Sakari Ailus wrote:
> > Hi Jacopo,
> 
> [snip]
> 
> > > 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.
> >
> 
> Please note that in this case there is only one pad that can handle
> multiplexed stream. The size of the routing table is the
> multiplication of the total number of pads by the product of all
> streams per pad. In this case (4 * (1 * 1 * 1 * 4))

Oh, good point, that's the case for G_ROUTING. I thought of S_ROUTING only.
:-)

> 
> > >
> > > With only one route per virtual channel active at a time.
> 
> [snip]
> 
> > >
> > > 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.
> >
> 
> Good!
> 
> > 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.
> >
> 
> I kind of like that! thanks!
> 
> > 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.
> >
> 
> Thanks, noted. I have been lazy and copied memset from other places in
> the ioctl handling code. I should check on your suggestions because I
> remember one of the many 0-initialization statement was a GCC specific one,
> don't remember which...

{} is GCC specific whereas { 0 } is not. But there have been long-standing
GCC bugs related to the use of { 0 } which is quite unfortunate --- they've
produced warnings or errors from code that is valid C...

-- 
Regards,

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
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 [this message]
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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