linux-kernel - Re: [PATCH 08/29] media: mfc: Add Exynos‑MFC driver probe support

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Message-ID: <CAJKOXPchnA2k4sghuSBxA4h=CKJEQU0=09F+AAxPxA-rBpUW_g@mail.gmail.com>
Date: Wed, 1 Oct 2025 08:06:01 +0900
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Himanshu Dewangan <h.dewangan@...sung.com>, mchehab@...nel.org, robh@...nel.org, 
	krzk+dt@...nel.org, conor+dt@...nel.org, sumit.semwal@...aro.org, 
	christian.koenig@....com, alim.akhtar@...sung.com, manjun@...sung.com, 
	nagaraju.s@...sung.com, ih0206.lee@...sung.com, jehyung.lee@...sung.com, 
	linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-samsung-soc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH 08/29] media: mfc: Add Exynos‑MFC driver probe support

On Wed, 1 Oct 2025 at 07:59, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On Wed, 1 Oct 2025 at 00:46, Marek Szyprowski <m.szyprowski@...sung.com> wrote:
> >
> > Hi Krzysztof,
> >
> > On 30.09.2025 07:54, Krzysztof Kozlowski wrote:
> > > On Tue, 30 Sept 2025 at 12:56, Himanshu Dewangan <h.dewangan@...sung.com> wrote:
> > >> From: Nagaraju Siddineni <nagaraju.s@...sung.com>
> > >>
> > >> Introduce a new Kconfig entry VIDEO_EXYNOS_MFC for the Samsung
> > >> Exynos MFC driver that supports firmware version 13 and later.
> > >> Extend the top‑level Samsung platform Kconfig to disable the legacy
> > >> S5P‑MFC driver when its firmware version is > v12 and to select the
> > >> new Exynos‑MFC driver only when VIDEO_SAMSUNG_S5P_MFC is not enabled.
> > >>
> > >> Add exynos-mfc Kconfig and Makefile for probe functionality and creation
> > >> of decoder and encoder device files by registering the driver object
> > >> exynos_mfc.o and other relevant source files.
> > >>
> > >> Provide header files mfc_core_ops.h and mfc_rm.h containing core
> > >>    operation prototypes, resource‑manager helpers,
> > >>    and core‑selection utilities.
> > >>
> > >> Add a configurable option MFC_USE_COREDUMP to enable core‑dump
> > >> support for debugging MFC errors.
> > >>
> > >> These changes bring support for newer Exynos‑based MFC hardware,
> > >> cleanly separate it from the legacy S5P‑MFC driver, and lay the
> > >> groundwork for future feature development and debugging.
> > >>
> > > No, NAK. Existing driver is well tested and already used on newest
> > > Exynos SoC, so all this new driver is exactly how you should not work
> > > in upstream. You need to integrate into existing driver.
> > >
> > > Samsung received this review multiple times already.
> >
> > Please don't be so categorical. The MFC hardware evolved quite a bit
> > from the ancient times of S5PV210 SoC, when s5p-mfc driver was designed.
> > The feature list of the new hardware hardly matches those and I really
> > don't see the reason for forcing support for so different hardware in a
> > single driver. Sometimes it is easier just to have 2 separate drivers if
> > the common part is just the acronym in the hardware block name...
> >
>
> I know it is easier for Samsung to write new driver, but this should
> answer to - why the maintainers and the community would like to
> maintain two drivers. Sure, make a case why we would like to take this
> code.
>
> The easiest argument here why we wouldn't is: new vendor downstream
> code means replicating all known issues, old coding style, everything
> which we already fixed and changed.

And 15 second look at one of the patches already confirmed this:
replicating downstream issue - undocumented DT ABI not following
current style, code relying on some other downstream drivers. 15
seconds was enough to find it.