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[89.233.230.99]) by smtp.gmail.com with ESMTPSA id s127sm14126874lfe.8.2019.01.09.14.40.39 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 09 Jan 2019 14:40:39 -0800 (PST) Date: Wed, 9 Jan 2019 23:40:39 +0100 From: Niklas =?iso-8859-1?Q?S=F6derlund?= To: Steve Longerbeam Cc: linux-media@vger.kernel.org, Mauro Carvalho Chehab , "open list:MEDIA DRIVERS FOR RENESAS - VIN" , open list Subject: Re: [RFC PATCH v2] media: rcar-vin: Allow independent VIN link enablement Message-ID: <20190109224039.GD24252@bigcity.dyn.berto.se> References: <20190106212018.16519-1-slongerbeam@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190106212018.16519-1-slongerbeam@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Hi Steve, Thanks for your patch, I think it looks good. On 2019-01-06 13:20:18 -0800, Steve Longerbeam wrote: > There is a block of code in rvin_group_link_notify() that loops through > all entities in the media graph, and prevents enabling a link to a VIN > node if any entity is in use. This prevents enabling a VIN link even if > there is an in-use entity somewhere in the graph that is independent of > the link's pipeline. > > For example, the code will prevent enabling a link from the first > rcar-csi2 receiver to a VIN node even if there is an enabled link > somewhere far upstream on the second independent rcar-csi2 receiver > pipeline. > > If this code is meant to prevent modifying a link if any entity in the > graph is actively involved in streaming (because modifying the CHSEL > register fields can disrupt any/all running streams), then the entities > stream counts should be checked rather than the use counts. > > (There is already such a check in __media_entity_setup_link() that verifies > the stream_count of the link's source and sink entities are both zero, > but that is insufficient, since there should be no running streams in > the entire graph). > > Modify the media_device_for_each_entity() loop to check the entity > stream_count instead of the use_count, and elaborate on the comment. > VIN node links can now be enabled even if there are other independent > in-use entities that are not streaming. > > Fixes: c0cc5aef31 ("media: rcar-vin: add link notify for Gen3") > > Signed-off-by: Steve Longerbeam Reviewed-by: Niklas Söderlund > --- > Changes in v2: > - bring back the media_device_for_each_entity() loop but check the > stream_count not the use_count. > --- > drivers/media/platform/rcar-vin/rcar-core.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c > index f0719ce24b97..6dd6b11c1b2b 100644 > --- a/drivers/media/platform/rcar-vin/rcar-core.c > +++ b/drivers/media/platform/rcar-vin/rcar-core.c > @@ -131,9 +131,13 @@ static int rvin_group_link_notify(struct media_link *link, u32 flags, > !is_media_entity_v4l2_video_device(link->sink->entity)) > return 0; > > - /* If any entity is in use don't allow link changes. */ > + /* > + * Don't allow link changes if any entity in the graph is > + * streaming, because modifying the CHSEL register fields > + * can disrupt running streams. > + */ > media_device_for_each_entity(entity, &group->mdev) > - if (entity->use_count) > + if (entity->stream_count) > return -EBUSY; > > mutex_lock(&group->lock); > -- > 2.17.1 > -- Regards, Niklas Söderlund