linux-kernel - Re: [PATCH 0/2] allow the sysfb support to be used in non-x86 arches

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Message-ID: <CAMj1kXGrDm5yN5eRZJ0YAjCde=0Xw7hobC9Oz5CNovo0sWuM+g@mail.gmail.com>
Date:   Mon, 24 May 2021 12:24:32 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Daniel Vetter <daniel@...ll.ch>,
        Peter Robinson <pbrobinson@...il.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Hans de Goede <hdegoede@...hat.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Russell King <linux@...linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-efi@...r.kernel.org,
        linux-riscv@...ts.infradead.org, x86@...nel.org
Subject: Re: [PATCH 0/2] allow the sysfb support to be used in non-x86 arches

Hello Javier,

On Fri, 21 May 2021 at 21:29, Javier Martinez Canillas
<javierm@...hat.com> wrote:
>
> The x86 architecture platform has a Generic System Framebuffers (sysfb)
> support, that register a system frambuffer platform devices. It either
> registers a "simple-framebuffer" for the simple{fb,drm} drivers or legacy
> VGA/EFI FB devices for the vgafb/efifb drivers.
>
> Besides this, the EFI initialization code used by other architectures such
> as aarch64 and riscv, has similar logic but only register an EFI FB device.
>
> The sysfb is generic enough to be reused by other architectures and can be
> moved out of the arch/x86 directory to drivers/firmware, allowing the EFI
> logic used by non-x86 architectures to be folded into sysfb as well.
>
> Patch #1 in this series do the former while patch #2 the latter. This has
> been tested on x86_64 and aarch64 machines using the efifb, simplefb and
> simpledrm drivers. But more testing will be highly appreciated, to make
> sure that no regressions are being introduced by these changes.
>
> Since this touches both arch/{x86,arm,arm64,riscv} and drivers/firmware, I
> don't know how it should be merged. But I didn't find a way to split these.
>

We could merge this via the EFI tree without too much risk of
conflicts, I think.

However, I'd like to see a better explanation of why this is an improvement.
The diffstat does not show a huge net win, and it does not enable
anything we didn't already have before, right?


>
> Javier Martinez Canillas (2):
>   drivers/firmware: move x86 Generic System Framebuffers support
>   drivers/firmware: consolidate EFI framebuffer setup for all arches
>
>  arch/arm/Kconfig                              |  1 +
>  arch/arm/include/asm/efi.h                    |  5 +-
>  arch/arm64/Kconfig                            |  1 +
>  arch/arm64/include/asm/efi.h                  |  5 +-
>  arch/riscv/Kconfig                            |  1 +
>  arch/riscv/include/asm/efi.h                  |  5 +-
>  arch/x86/Kconfig                              | 27 +-----
>  arch/x86/kernel/Makefile                      |  3 -
>  drivers/firmware/Kconfig                      | 30 +++++++
>  drivers/firmware/Makefile                     |  2 +
>  drivers/firmware/efi/Makefile                 |  2 +
>  drivers/firmware/efi/efi-init.c               | 90 -------------------
>  .../firmware/efi}/sysfb_efi.c                 | 79 +++++++++++++++-
>  {arch/x86/kernel => drivers/firmware}/sysfb.c | 42 +++++----
>  .../firmware}/sysfb_simplefb.c                | 31 ++++---
>  .../x86/include/asm => include/linux}/sysfb.h | 34 +++----
>  16 files changed, 182 insertions(+), 176 deletions(-)
>  rename {arch/x86/kernel => drivers/firmware/efi}/sysfb_efi.c (84%)
>  rename {arch/x86/kernel => drivers/firmware}/sysfb.c (70%)
>  rename {arch/x86/kernel => drivers/firmware}/sysfb_simplefb.c (82%)
>  rename {arch/x86/include/asm => include/linux}/sysfb.h (68%)
>
> --
> 2.31.1
>