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

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Message-ID: <CAJKOXPe0kGFoUxOGupwD_rSshTBVFhH3184xOH=NquSGn2QxcQ@mail.gmail.com>
Date: Wed, 1 Oct 2025 07:59:07 +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 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.