linux-kernel - [PATCH v2 0/2] Associate ddc adapters with connectors

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Message-Id: <cover.1561458051.git.andrzej.p@collabora.com>
Date:   Tue, 25 Jun 2019 12:24:39 +0200
From:   Andrzej Pietrasiewicz <andrzej.p@...labora.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     kernel@...labora.com, m.szyprowski@...sung.com,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Inki Dae <inki.dae@...sung.com>,
        Joonyoung Shim <jy0922.shim@...sung.com>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org
Subject: [PATCH v2 0/2] Associate ddc adapters with connectors

It is difficult for a user to know which of the i2c adapters is for which
drm connector. This series addresses this problem.

The idea is to have a symbolic link in connector's sysfs directory, e.g.:

ls -l /sys/class/drm/card0-HDMI-A-1/ddc
lrwxrwxrwx 1 root root 0 Jun 24 10:42 /sys/class/drm/card0-HDMI-A-1/ddc \
	-> ../../../../soc/13880000.i2c/i2c-2

The user then knows that their card0-HDMI-A-1 uses i2c-2 and can e.g. run
ddcutil:

ddcutil -b 2 getvcp 0x10
VCP code 0x10 (Brightness                    ): current value =    90, max value =   100

The first patch in the series adds struct i2c_adapter pointer to struct
drm_connector. If the field is used by a particular driver, then an
appropriate symbolic link is created by the generic code, which is also added
by this patch.

The second patch is an example of how to convert a driver to this new scheme.

v1..v2:

- used fixed name "ddc" for the symbolic link in order to make it easy for
userspace to find the i2c adapter

Andrzej Pietrasiewicz (2):
  drm: Include ddc adapter pointer in struct drm_connector
  drm/exynos: Provide ddc symlink in connector's sysfs

 drivers/gpu/drm/drm_sysfs.c          |  7 +++++++
 drivers/gpu/drm/exynos/exynos_hdmi.c | 11 +++++------
 include/drm/drm_connector.h          | 11 +++++++++++
 3 files changed, 23 insertions(+), 6 deletions(-)

-- 
2.17.1