Re: [PATCH v2 13/13] ARM: s3c24xx: camif: include header with prototypes and unify declaration

From: Krzysztof Kozlowski <krzk@kernel.org>
To: Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Tomasz Figa <tomasz.figa@gmail.com>,
	Will Deacon <will@kernel.org>,
	linux-clk <linux-clk@vger.kernel.org>,
	LINUXWATCHDOG <linux-watchdog@vger.kernel.org>,
	"moderated list:ARM/SAMSUNG EXYNOS ARM ARCHITECTURES"
	<linux-samsung-soc@vger.kernel.org>,
	Sylwester Nawrocki <snawrocki@kernel.org>,
	Cedric Roux <sed@free.fr>, Russell King <linux@armlinux.org.uk>,
	linux-stm32@st-md-mailman.stormreply.com,
	Lihua Yao <ylhuajnu@outlook.com>,
	Chanwoo Choi <cw00.choi@samsung.com>,
	Kukjin Kim <kgene@kernel.org>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Guenter Roeck <linux@roeck-us.net>,
	Sergio Prado <sergio.prado@e-labworks.com>,
	Alexandre Torgue <alexandre.torgue@st.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Wim Van Sebroeck <wim@linux-watchdog.org>,
	Simtec Linux Team <linux@simtec.co.uk>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Stephen Boyd <sboyd@kernel.org>,
	patches@opensource.cirrus.com,
	Kyungmin Park <kyungmin.park@samsung.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>
Subject: Re: [PATCH v2 13/13] ARM: s3c24xx: camif: include header with prototypes and unify declaration
Date: Wed, 12 Aug 2020 15:31:09 +0200	[thread overview]
Message-ID: <20200812133109.GA15697@pi3> (raw)
In-Reply-To: <6ccf14a9-802f-25b8-494d-e957cafd073d@samsung.com>

On Wed, Aug 12, 2020 at 03:11:41PM +0200, Sylwester Nawrocki wrote:
> On 12.08.2020 13:28, Arnd Bergmann wrote:
> > On Wed, Aug 12, 2020 at 12:46 PM Sylwester Nawrocki
> > <s.nawrocki@samsung.com> wrote:
> >> On 12.08.2020 11:14, Arnd Bergmann wrote:
> >>>
> >>> It seems there have never been any callers and the entire file
> >>> can just be removed, with the rest of that platform_data header
> >>> file moved to drivers/media/platform/s3c-camif/.
> >>
> >> Yes, it seems that patch never made it to mainline:
> >> https://protect2.fireeye.com/v1/url?k=abe5f73a-f6293cfe-abe47c75-0cc47a314e9a-7fafe832d055d852&q=1&e=2596ffb6-c4cb-492a-8c6f-a0e261567842&u=https%3A%2F%2Fgit.linuxtv.org%2Fsnawrocki%2Fmedia.git%2Fcommit%2F%3Fh%3Dtesting%2Fs3c-camif%26id%3D355cbf835aff2aabf78390931cbbaa608af77967
> > 
> > I suppose it would still apply if anyone was interested, but I see your
> > point.
> > 
> >> I doubt there are still users of camera on the s3c2440 boards
> >> with current mainline kernels, if any at all, there are much
> >> better HW alternatives right now.
> > 
> > I see two board files (and no DT) instantiate the camif device:
> > NexVision Nexcoder 2440 and the FriendlyARM mini2440.
> > 
> > Can you say whether the camif on those would actually work
> > at all without your patch? If not, we know that there are no
> > users of that driver and could either drop it completely or move
> > it to staging for a release or two.
> 
> Without additional patches the camif will not work, the driver 
> needs an instance of struct s3c_camif_plat_data which specifies
> what image sensor is attached.
> 
> I think we can drop the driver, together with the s3c_camif_device
> platform device definitions. It can always be added again if anyone
> ever needs it or converts the platform to DT.

Since the header was in /include/media I assumed there might be some
user-space tools using it. But if it is not the case, I'll drop the code
then.

> IMO all non-DT code in arch/arm/mach-s3c24xx is a candidate for
> removal, it just adds to the maintenance effort and I seriously
> doubt there are now any users of it.

That is quite tricky... I really do not know whether there are any real
world users of S3C24xx and S3C64xx platforms. Evalkits are mostly not
available for buying so I do not expect new designs. However still
existing ones might be somewhere... Few years ago, back in Samsung, I
mentioned removing them. That time I think Marek or you Sylwester, said
that there are industrial applications using S3C24xx. I believe, why
not. The trouble is - how to find such users? How to get in touch for
testing or at least for bug reports if something is broken?

Or even more important - is it worth to spend effort and time on this?
If there is no single production system using recent Linux kernel, the
answer should be negative...

Best regards,
Krzysztof

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