linux-kernel - [PATCH v2 0/8] drm: fb-helper/ssd130x: Add support for DRM_FORMAT

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Date:   Thu, 24 Aug 2023 17:08:38 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Javier Martinez Canillas <javierm@...hat.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: [PATCH v2 0/8] drm: fb-helper/ssd130x: Add support for DRM_FORMAT_R1

        Hi all,

The native display format of ssd1306 OLED displays is monochrome
light-on-dark (R1).  This patch series adds support for the R1 buffer
format to both the ssd130x DRM driver and the FB helpers, so monochrome
applications (including fbdev emulation and the text console) not only
look better, but also avoid the overhead of back-and-forth conversions
between R1 and XR24.

This series consists of 4 parts:
  - Patches 1-2 contain fixes,
  - Patch 3 contains a small improvement,
  - Patch 4 adds R1 support to the ssd130x DRM driver,
  - Patches 5-6 update the DRM client and FB helper code to avoid
    calling drm_mode_legacy_fb_format() where the exact buffer format is
    already known, to prepare for R1 support,
  - Patch 7 adds support for R1 to fbdev emulation and the text console,
  - Patch 8 switches ssd130x to R1 for fbdev emulation and the text
    console.

Changes compared to v1[1]:
  - Drop "[PATCH 1/8] drm/ssd130x: Fix pitch calculation in
    ssd130x_fb_blit_rect()" (already applied),
  - Drop "[PATCH/RFC 3/8] drm/ssd130x: Bail out early if data_array is
    not yet available" (no longer needed),
  - New patch "[PATCH v2 2/8] drm/ssd130x: Fix screen clearing",
  - New patch "[PATCH v2 3/8] drm/ssd130x: Use bool for
    ssd130x_deviceinfo flags",
  - Add Reviewed-by, Tested-by,
  - Rework on top op commit 8c3926367ac9df6c ("drm/ssd130x: Use
    shadow-buffer helpers when managing plane's state") in drm/drm-next,
  - Do not allocate intermediate buffer when not needed,
  - s/drm_mode_create_dumb/drm_client_buffer_addfb/ in one-line summary,
  - Fix accidental debug level increase.

This has been tested on an Adafruit FeatherWing 128x32 OLED, connected
to an OrangeCrab ECP5 FPGA board running a 64 MHz VexRiscv RISC-V
softcore, using the fbdev text console.

Thanks for your comments!

P.S. Note that the biggest hurdle was the copious use of the
     drm_mode_legacy_fb_format() helper in various places.  This helper
     cannot decide between C1 and R1 without knowledge of the
     capabilities of the full display pipeline.  Instead of
     special-casing its return value in three callers, I did so in only
     one place, and got rid of two of these calls in the call chain.
     I think Thomas' grand plan is to replace preferred_{bpp,depth} by a
     preferred fourcc format? That would simplify things a lot...

[1] "[PATCH 0/8] drm: fb-helper/ssd130x: Add support for DRM_FORMAT_R1"
    https://lore.kernel.org/r/cover.1689252746.git.geert@linux-m68k.org

Geert Uytterhoeven (8):
  drm/dumb-buffers: Fix drm_mode_create_dumb() for bpp < 8
  drm/ssd130x: Fix screen clearing
  drm/ssd130x: Use bool for ssd130x_deviceinfo flags
  drm/ssd130x: Add support for DRM_FORMAT_R1
  drm/client: Convert drm_client_buffer_addfb() to drm_mode_addfb2()
  drm/fb-helper: Pass buffer format via drm_fb_helper_surface_size
  drm/fb-helper: Add support for DRM_FORMAT_R1
  drm/ssd130x: Switch preferred_bpp/depth to 1

 drivers/gpu/drm/drm_client.c        |  13 ++-
 drivers/gpu/drm/drm_dumb_buffers.c  |   3 +-
 drivers/gpu/drm/drm_fb_helper.c     |  42 ++++++---
 drivers/gpu/drm/drm_fbdev_generic.c |   9 +-
 drivers/gpu/drm/solomon/ssd130x.c   | 127 ++++++++++++++++++++--------
 drivers/gpu/drm/solomon/ssd130x.h   |   4 +-
 include/drm/drm_fb_helper.h         |   2 +
 7 files changed, 138 insertions(+), 62 deletions(-)

-- 
2.34.1

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds