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From: Sakari Ailus <sakari.ailus@linux.intel.com>
To: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	linux-media@vger.kernel.org,
	Jacopo Mondi <jacopo+renesas@jmondi.org>,
	niklas.soderlund+renesas@ragnatech.se,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Hans Verkuil <hverkuil-cisco@xs4all.nl>
Subject: Re: [PATCH v5 12/24] media: entity: Add an iterator helper for connected pads
Date: Thu, 29 Apr 2021 15:07:19 +0300
Message-ID: <20210429120719.GX3@paasikivi.fi.intel.com> (raw)
In-Reply-To: <a23d4695-5629-034a-c9a0-804533518b9e@ideasonboard.com>

On Thu, Apr 29, 2021 at 03:04:38PM +0300, Tomi Valkeinen wrote:
> On 29/04/2021 14:56, Sakari Ailus wrote:
> > Hi Laurent,
> > 
> > On Thu, Apr 29, 2021 at 04:33:48AM +0300, Laurent Pinchart wrote:
> > > Hi Sakari,
> > > 
> > > On Tue, Apr 20, 2021 at 02:48:25PM +0300, Sakari Ailus wrote:
> > > > On Sun, Apr 18, 2021 at 09:20:03PM +0300, Laurent Pinchart wrote:
> > > > > On Thu, Apr 15, 2021 at 04:04:38PM +0300, Tomi Valkeinen wrote:
> > > > > > From: Sakari Ailus <sakari.ailus@linux.intel.com>
> > > > > > 
> > > > > > Add a helper macro for iterating over pads that are connected through
> > > > > > enabled routes. This can be used to find all the connected pads within an
> > > > > > entity, for instance starting from the pad which has been obtained during
> > > > > > the graph walk.
> > > > > > 
> > > > > > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > > > > > Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
> > > > > > 
> > > > > > - Make __media_entity_next_routed_pad() return NULL and adjust the
> > > > > >    iterator to handle that
> > > > > > Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> > > > > > ---
> > > > > >   include/media/media-entity.h | 27 +++++++++++++++++++++++++++
> > > > > >   1 file changed, 27 insertions(+)
> > > > > > 
> > > > > > diff --git a/include/media/media-entity.h b/include/media/media-entity.h
> > > > > > index 73de1c335e4e..edd6f60ed6b4 100644
> > > > > > --- a/include/media/media-entity.h
> > > > > > +++ b/include/media/media-entity.h
> > > > > > @@ -916,6 +916,33 @@ __must_check int media_graph_walk_init(
> > > > > >   bool media_entity_has_route(struct media_entity *entity, unsigned int pad0,
> > > > > >   			    unsigned int pad1);
> > > > > > +static inline struct media_pad *__media_entity_next_routed_pad(
> > > > > > +	struct media_pad *start, struct media_pad *iter)
> > > > > > +{
> > > > > > +	struct media_entity *entity = start->entity;
> > > > > > +
> > > > > > +	for (; iter < &entity->pads[entity->num_pads]; iter++)
> > > > > > +		if (media_entity_has_route(entity, start->index, iter->index))
> > > > > > +			return iter;
> > > > > 
> > > > > I'd use curly braces.
> > > > > 
> > > > > > +
> > > > > > +	return NULL;
> > > > > > +}
> > > > > 
> > > > > Does this need to be inlined ?
> > > > 
> > > > I guess it doesn't have to. It's used inside loops and it's rather small so
> > > > I think it should be fine that way.
> > > 
> > > It may not be that small. I'd rather let the compiler decide whether to
> > > inline it or not.
> > 
> > Works for me.
> > 
> > > 
> > > > > > +
> > > > > > +/**
> > > > > > + * media_entity_for_each_routed_pad - Iterate over entity pads connected by routes
> > > > > 
> > > > > "routed" sounds a bit weird. Would media_entity_for_each_connected_pad()
> > > > > be a better name ?
> > > > 
> > > > "Connected" is often used in context of links. We're dealing with routes
> > > > here, so I thought "routed" is appropriate to avoid confusion.
> > > 
> > > I understand the confusion, maybe we can find a better term that would
> > > be different than "connected". "routed" really sounds weird in this
> > > context.
> > 
> > I'm fine with connected.
> > 
> > > 
> > > > > > + *
> > > > > > + * @start: The stating pad
> > > > > 
> > > > > s/stating/starting/
> > > > > 
> > > > > > + * @iter: The iterator pad
> > > > > > + *
> > > > > > + * Iterate over all pads connected through routes from a given pad
> > > > > 
> > > > > "from the @start pad"
> > > > > 
> > > > > > + * within an entity. The iteration will include the starting pad itself.
> > > > > 
> > > > > s/starting/@start/
> > > > > 
> > > > > I wonder if it wouldn't be more logical to not include the start pad.
> > > > > That wouldn't match the current usage patterns, which would need to be
> > > > > adapted accordingly, but I'm worried that including the start pad will
> > > > > lead to annoying bugs in the future. Maybe I worry too much.
> > > > 
> > > > The aim here is to find all pads that are routed to another pad within the
> > > > same entity. If you remove the start pad, it becomes a task harder than
> > > > difficult.
> > > 
> > > Intuitively, "all pads that are routed to another pad" doesn't include
> > > the "another pad". I'm not opposed to including the start pad as that's
> > > what the current usage patterns need, but we should then rename the
> > > macro accordingly as its current name is counter-intuitive.
> > 
> > I'm certainly not opposed to that. But it shouldn't be too much longer than
> > what's already there.
> > 
> > > 
> > > > > And now that I reread the patch, I also wonder if "start" is a good
> > > > > name, as it implies we start the enumeration from a given pad, while we
> > > > > enumerate all pads connected to a given pad. I'm not sure what a better
> > > > > name would be though, maybe just pad ?
> > > > 
> > > > There are two pads here. Therefore explicitly calling them something else
> > > > makes sense IMO.
> > > 
> > > Makes sense, but "start" isn't a good name as we're not starting
> > > anything.
> > 
> > "start" is not a verb here. It's where the iteration *starts*.
> 
> Hmm, no, the 'start' is a filter here, isn't it? The macro iterates over all
> pads which have a route to 'start'.

The iteration starts from "start", but it does not return all pads, only
the connected ones.

But feel free to use another name if you have a better one.

-- 
Sakari Ailus

  reply index

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-15 13:04 [PATCH v5 00/24] v4l: subdev internal routing Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 01/24] media: entity: Use pad as a starting point for graph walk Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 02/24] media: entity: Use pads instead of entities in the media graph walk stack Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 03/24] media: entity: Walk the graph based on pads Tomi Valkeinen
2021-04-18 17:47   ` Laurent Pinchart
2021-04-20 11:30     ` Sakari Ailus
2021-04-15 13:04 ` [PATCH v5 04/24] v4l: mc: Start walk from a specific pad in use count calculation Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 05/24] media: entity: Add iterator helper for entity pads Tomi Valkeinen
2021-04-18 17:52   ` Laurent Pinchart
2021-04-22 12:04     ` Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 06/24] media: entity: Move the pipeline from entity to pads Tomi Valkeinen
2021-04-18 18:00   ` Laurent Pinchart
2021-04-20 11:38     ` Sakari Ailus
2021-04-15 13:04 ` [PATCH v5 07/24] media: entity: Use pad as the starting point for a pipeline Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 08/24] media: entity: Add has_route entity operation Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 09/24] media: entity: Add media_entity_has_route() function Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 10/24] media: entity: Use routing information during graph traversal Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 11/24] media: entity: Skip link validation for pads to which there is no route to Tomi Valkeinen
2021-04-18 18:06   ` Laurent Pinchart
2021-04-20 11:41     ` Sakari Ailus
2021-04-23 12:37       ` Tomi Valkeinen
2021-04-29 12:06         ` Sakari Ailus
2021-04-29 14:10           ` Laurent Pinchart
2021-04-15 13:04 ` [PATCH v5 12/24] media: entity: Add an iterator helper for connected pads Tomi Valkeinen
2021-04-18 18:20   ` Laurent Pinchart
2021-04-20 11:48     ` Sakari Ailus
2021-04-29  1:33       ` Laurent Pinchart
2021-04-29 11:56         ` Sakari Ailus
2021-04-29 12:04           ` Tomi Valkeinen
2021-04-29 12:07             ` Sakari Ailus [this message]
2021-04-29 12:14               ` Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 13/24] media: entity: Add only connected pads to the pipeline Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 14/24] media: entity: Add debug information in graph walk route check Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 15/24] v4l: Add bus type to frame descriptors Tomi Valkeinen
2021-04-18 19:23   ` Laurent Pinchart
2021-04-20 11:50     ` Sakari Ailus
2021-04-22 12:30       ` Tomi Valkeinen
2021-04-29 11:58         ` Sakari Ailus
2021-04-29 14:09           ` Laurent Pinchart
2021-04-15 13:04 ` [PATCH v5 16/24] v4l: Add CSI-2 bus configuration " Tomi Valkeinen
2021-04-18 19:24   ` Laurent Pinchart
2021-04-20 16:32     ` Sakari Ailus
2021-04-15 13:04 ` [PATCH v5 17/24] v4l: Add stream to frame descriptor Tomi Valkeinen
2021-04-18 19:27   ` Laurent Pinchart
2021-04-22 12:47     ` Tomi Valkeinen
2021-04-22 16:18       ` Laurent Pinchart
2021-04-15 13:04 ` [PATCH v5 18/24] v4l: subdev: Add [GS]_ROUTING subdev ioctls and operations Tomi Valkeinen
2021-04-18 18:32   ` Laurent Pinchart
2021-04-22 11:16     ` Tomi Valkeinen
2021-04-22 16:20       ` Laurent Pinchart
2021-04-22 16:58         ` Tomi Valkeinen
2021-04-20 16:35   ` Sakari Ailus
2021-04-15 13:04 ` [PATCH v5 19/24] media: Documentation: Add GS_ROUTING documentation Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 20/24] v4l: mc: Add an S_ROUTING helper function for power state changes Tomi Valkeinen
2021-04-18 18:55   ` Laurent Pinchart
2021-04-20 16:41     ` Sakari Ailus
2021-04-15 13:04 ` [PATCH v5 21/24] v4l: subdev: routing kernel helper functions Tomi Valkeinen
2021-04-18 19:18   ` Laurent Pinchart
2021-04-15 13:04 ` [PATCH v5 22/24] v4l: subdev: add v4l2_subdev_get_format_dir() Tomi Valkeinen
2021-04-18 19:04   ` Laurent Pinchart
2021-04-21 13:04     ` Tomi Valkeinen
2021-04-29  1:43       ` Laurent Pinchart
2021-05-04  6:49         ` Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 23/24] v4l: subdev: Take routing information into account in link validation Tomi Valkeinen
2021-04-15 13:04 ` [PATCH v5 24/24] v4l: subdev: increase V4L2_FRAME_DESC_ENTRY_MAX to 8 Tomi Valkeinen
2021-04-18 19:06   ` Laurent Pinchart
2021-04-16  8:38 ` [PATCH v5 00/24] v4l: subdev internal routing Niklas Söderlund
2021-04-16  8:47   ` Tomi Valkeinen
2021-04-16  8:56     ` Niklas Söderlund
2021-04-18 17:32 ` Laurent Pinchart
2021-04-21 12:57   ` Tomi Valkeinen
2021-04-29  1:27     ` Laurent Pinchart

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