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Date: Fri, 5 Jan 2024 10:34:20 +0300
From: Dan Carpenter <dan.carpenter@linaro.org>
To: Hidenori Kobayashi <hidenorik@chromium.org>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>,
	Bingbu Cao <bingbu.cao@intel.com>,
	Tianshu Qiu <tian.shu.qiu@intel.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-media@vger.kernel.org, linux-staging@lists.linux.dev,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] media: staging: ipu3-imgu: Set fields before
 media_entity_pads_init()
Message-ID: <a6f9ff72-421a-42c6-b24a-3dbf5a55e631@moroto.mountain>
References: <20231228093926.748001-1-hidenorik@chromium.org>
 <27f1c487-78cc-4e56-ba79-1434aba131fd@moroto.mountain>
 <20240105021856.wpzmwtyzxzqfznrp@google.com>
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On Fri, Jan 05, 2024 at 11:19:23AM +0900, Hidenori Kobayashi wrote:
> On Thu, Jan 04, 2024 at 01:04:27PM +0300, Dan Carpenter wrote:
> > On Thu, Dec 28, 2023 at 06:39:25PM +0900, Hidenori Kobayashi wrote:
> > > The pad's flags is checked in media_entity_pads_init(), so it has to be
> > > initialized beforehand. The ops initialization is also moved together
> > > for readability.
> > > 
> > 
> > How does this bug look like to a user?  What is the Fixes tag?  Does
> > this need to be backported to stable?
> 
> I suppose I should have included those in the commit message.
> 
> 1) To a user, the imgu driver fails to probe with the following message:
> 
> [   14.596315] ipu3-imgu 0000:00:05.0: failed initialize subdev media entity (-22)
> [   14.596322] ipu3-imgu 0000:00:05.0: failed to register subdev0 ret (-22)
> [   14.596327] ipu3-imgu 0000:00:05.0: failed to register pipes (-22)
> [   14.596331] ipu3-imgu 0000:00:05.0: failed to create V4L2 devices (-22)
> 

Yeah.  This is super useful information.

> 2) Re Fixes tag, I see that the first commit of imgu driver already
> initializes the flags after media_entity_pads_init(). The documentation
> of this API ( "Drivers must set the direction of every pad ... before
> calling media_entity_pads_init") predates the first commit. So, I guess
> 
> Fixes: a0ca1627b450 ("media: staging/intel-ipu3: Add v4l2 driver based on media framework")
> 
> 3) Re stable, I was not sure. The probe failure only appears after a
> check was added by Commit deb866f9e3a45ae058b21765feeffae6aea6a193. That
> check is not in linux-6.6.y branch. So I was not sure if this counts as
> "a real bug that bothers people" mentioned in the document.

Hm...  I don't know either.  Wait for a day and see if anyone else has
an opinion then listen to your gut and resend with whatever your gut
says?

regards,
dan carpenter