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[155.4.209.203]) by smtp.gmail.com with ESMTPSA id b10sm32549lfi.20.2020.06.17.08.28.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Jun 2020 08:28:58 -0700 (PDT) Date: Wed, 17 Jun 2020 17:28:57 +0200 From: Niklas =?iso-8859-1?Q?S=F6derlund?= To: Michael Rodin Cc: Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org, michael@rodin.online, efriedrich@de.adit-jv.com, erosca@de.adit-jv.com, Steve Longerbeam Subject: Re: [PATCH] media: rcar-vin: Move media_device_register to async completion Message-ID: <20200617152857.GA2936315@oden.dyn.berto.se> References: <1592328696-84533-1-git-send-email-mrodin@de.adit-jv.com> <20200617105646.GB2850317@oden.dyn.berto.se> <20200617151537.GB88066@vmlxhi-121.adit-jv.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200617151537.GB88066@vmlxhi-121.adit-jv.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Michael, On 2020-06-17 17:15:37 +0200, Michael Rodin wrote: > Hi Niklas and Steve, > > On Wed, Jun 17, 2020 at 12:56:46PM +0200, Niklas Söderlund wrote: > > Hi Michael and Steve, > > > > On 2020-06-16 19:31:36 +0200, Michael Rodin wrote: > > > From: Steve Longerbeam > > > > > > The media_device is registered during driver probe, before async > > > completion, so it is possible for .link_notify to be called before > > > all devices are bound. > > > > > > Fix this by moving media_device_register() to rvin_group_notify_complete(). > > > This ensures that all devices are now bound (the rcar-csi2 subdevices and > > > and video capture devices) before .link_notify can be called. > > > > I'm curious to what situation created the need for this change. I'm > > currently trying to take the VIN driver in the opposite direction [1] > > with the end goal of registering video devices at probe time and then > > allow the media graph to populate as devices becomes available. > > It looks like almost all platform drivers call media_device_register() in > the completion callback. From my understaning it is necessary to ensure > that all subdevices are bound and all links are created before the user > can enable any link (which would trigger link_notify callback execution) > and set formats. If I am not mistaken, Steve could observe an "OOPS" or > at least it is theoretically possible. If an OOPS have been observed I would be interested to see it. That way we can fix the OOPS and keep the media graph registration where it is today. > > Actually I found that this patch alone is not enough even if it is correct, > because we also have to register the media device in rvin_parallel_notify_complete() > in case if there is only a parallel video input device attached. > > > My reason for this is that we could have a functional pipeline inside > > the graph even if it's not complete. This came out of the GMSL work done > > a while pack where I had a faulty camera that would prevent the other 7 > > in the system to function. > > I agree that if a probe of a faulty subdevice fails, this should not affect > functionality of the other attached subdevices. The "complete" callback of > the async notifier is probably not executed in this case, so I guess, we > would have to register the media device in the "bound" callback after the first > subdevice has been probed? Otherwise there is not much sense to have video > capture devices, which are not connected to any source. Calling it in the bound callback is mostly the same as it is today, as link_notify could then be called when not all entities are in the graph. In fact even if we where tp move the media device registration to the t complete callback we have this problem if any of the subdevices are unbound. Then we are back to the state with a registerd media device where not all entities are present. I think the solution here is to address the issue (if any) in the link_notify callback when the graph is not fully populated. > > (Delayed) population of the media graph after media device registration > sounds also like a requirement for device tree overlay support, which would > also be a nice feature. > > > 1. [PATCH 0/5] media-device: Report if graph is complete > > > > > > > > Signed-off-by: Steve Longerbeam > > > Signed-off-by: Michael Rodin > > > --- > > > drivers/media/platform/rcar-vin/rcar-core.c | 14 ++++++-------- > > > 1 file changed, 6 insertions(+), 8 deletions(-) > > > > > > diff --git a/drivers/media/platform/rcar-vin/rcar-core.c b/drivers/media/platform/rcar-vin/rcar-core.c > > > index 7440c89..e70f83b 100644 > > > --- a/drivers/media/platform/rcar-vin/rcar-core.c > > > +++ b/drivers/media/platform/rcar-vin/rcar-core.c > > > @@ -253,7 +253,6 @@ static int rvin_group_init(struct rvin_group *group, struct rvin_dev *vin) > > > struct media_device *mdev = &group->mdev; > > > const struct of_device_id *match; > > > struct device_node *np; > > > - int ret; > > > > > > mutex_init(&group->lock); > > > > > > @@ -266,7 +265,6 @@ static int rvin_group_init(struct rvin_group *group, struct rvin_dev *vin) > > > vin_dbg(vin, "found %u enabled VIN's in DT", group->count); > > > > > > mdev->dev = vin->dev; > > > - mdev->ops = &rvin_media_ops; > > > > > > match = of_match_node(vin->dev->driver->of_match_table, > > > vin->dev->of_node); > > > @@ -278,11 +276,7 @@ static int rvin_group_init(struct rvin_group *group, struct rvin_dev *vin) > > > > > > media_device_init(mdev); > > > > > > - ret = media_device_register(&group->mdev); > > > - if (ret) > > > - rvin_group_cleanup(group); > > > - > > > - return ret; > > > + return 0; > > > } > > > > > > static void rvin_group_release(struct kref *kref) > > > @@ -688,6 +682,8 @@ static int rvin_group_notify_complete(struct v4l2_async_notifier *notifier) > > > return ret; > > > } > > > > > > + vin->group->mdev.ops = &rvin_media_ops; > > > + > > > /* Register all video nodes for the group. */ > > > for (i = 0; i < RCAR_VIN_NUM; i++) { > > > if (vin->group->vin[i] && > > > @@ -736,8 +732,10 @@ static int rvin_group_notify_complete(struct v4l2_async_notifier *notifier) > > > } > > > } > > > mutex_unlock(&vin->group->lock); > > > + if (ret) > > > + return ret; > > > > > > - return ret; > > > + return media_device_register(&vin->group->mdev); > > > } > > > > > > static void rvin_group_notify_unbind(struct v4l2_async_notifier *notifier, > > > -- > > > 2.7.4 > > > > > > > -- > > Regards, > > Niklas Söderlund > > -- > Best Regards, > Michael -- Regards, Niklas Söderlund