From: Hans Verkuil <firstname.lastname@example.org>
To: Mauro Carvalho Chehab <email@example.com>
Cc: Javier Martinez Canillas <firstname.lastname@example.org>,
Tian Shu Qiu <email@example.com>,
Sakari Ailus <firstname.lastname@example.org>,
Mauro Carvalho Chehab <email@example.com>,
Jian Xu Zheng <firstname.lastname@example.org>,
Yong Zhi <email@example.com>, Bingbu Cao <firstname.lastname@example.org>,
Subject: Re: [PATCH 0/2] media: intel-ipu3: allow the media graph to be used even if a subdev fails
Date: Thu, 27 Sep 2018 12:22:37 +0200 [thread overview]
Message-ID: <email@example.com> (raw)
On 09/27/2018 12:13 PM, Mauro Carvalho Chehab wrote:
> Em Thu, 27 Sep 2018 11:52:35 +0200
> Hans Verkuil <firstname.lastname@example.org> escreveu:
>> Hi Javier,
>> On 09/04/2018 01:30 PM, Javier Martinez Canillas wrote:
>>> This series allows the ipu3-cio2 driver to properly expose a subset of the
>>> media graph even if some drivers for the pending subdevices fail to probe.
>>> Currently the driver exposes a non-functional graph since the pad links are
>>> created and the subdev dev nodes are registered in the v4l2 async .complete
>>> callback. Instead, these operations should be done in the .bound callback.
>>> Patch #1 just adds a v4l2_device_register_subdev_node() function to allow
>>> registering a single device node for a subdev of a v4l2 device.
>>> Patch #2 moves the logic of the ipu3-cio2 .complete callback to the .bound
>>> callback. The .complete callback is just removed since is empy after that.
>> Sorry, I missed this series until you pointed to it on irc just now :-)
>> I have discussed this topic before with Sakari and Laurent. My main problem
>> with this is how an application can discover that not everything is online?
>> And which parts are offline?
> Via the media controller? It should be possible for an application to see
> if a videonode is missing using it.
>> Perhaps a car with 10 cameras can function with 9, but not with 8. How would
>> userspace know?
> I guess this is not the only case where someone submitted a patch for
> a driver that would keep working if some device node registration fails.
> It could be just déjà vu, but I have a vague sensation that I merged something
> similar to it in the past on another driver, but I can't remember any details.
>> I completely agree that we need to support these advanced scenarios (including
>> what happens when a camera suddenly fails), but it is the userspace aspects
>> for which I would like to see an RFC first before you can do these things.
> Dynamic runtime fails should likely rise some signal. Perhaps a sort of
> media controller event?
See this old discussion: https://patchwork.kernel.org/patch/9849317/
My point is that someone needs to think about this and make a proposal.
There may well be a simple approach, but it needs to be specced first.
>>> Best regards,
>>> Javier Martinez Canillas (2):
>>> [media] v4l: allow to register dev nodes for individual v4l2 subdevs
>>> media: intel-ipu3: create pad links and register subdev nodes at bound
>>> drivers/media/pci/intel/ipu3/ipu3-cio2.c | 66 ++++++-----------
>>> drivers/media/v4l2-core/v4l2-device.c | 90 ++++++++++++++----------
>>> include/media/v4l2-device.h | 10 +++
>>> 3 files changed, 85 insertions(+), 81 deletions(-)
next prev parent reply other threads:[~2018-09-27 10:22 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-04 11:30 [PATCH 0/2] media: intel-ipu3: allow the media graph to be used even if a subdev fails Javier Martinez Canillas
2018-09-04 11:30 ` [PATCH 1/2] [media] v4l: allow to register dev nodes for individual v4l2 subdevs Javier Martinez Canillas
2018-09-17 16:46 ` Sakari Ailus
2018-09-17 17:13 ` Javier Martinez Canillas
2018-09-04 11:30 ` [PATCH 2/2] media: intel-ipu3: create pad links and register subdev nodes at bound time Javier Martinez Canillas
2018-09-17 16:21 ` [PATCH 0/2] media: intel-ipu3: allow the media graph to be used even if a subdev fails Javier Martinez Canillas
2018-09-27 9:52 ` Hans Verkuil
2018-09-27 10:13 ` Mauro Carvalho Chehab
2018-09-27 10:22 ` Hans Verkuil [this message]
2018-11-14 8:28 ` Tomasz Figa
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