Re: [PATCH v6 00/24] Associate ddc adapters with connectors

[Emil Velikov <emil.l.velikov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 2019/07/26, Andrzej Pietrasiewicz wrote:
> 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.
> 
> Patch 2 adds a new variant of drm_connector_init(), see the changelog
> below.
> 
> Patches 3..24 are examples 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
> 
> v2..v3:
> 
> - converted as many drivers as possible.
> 
> v3..v4:
> 
> - added Reviewed-by for patch 01/23
> - moved "ddc" field assignment to before drm_connector_init() is called
> in msm, vc4, sti, mgag200, ast, amdgpu, radeon
> - simplified the code in amdgpu and radeon at the expense of some lines
> exceeding 80 characters as per Alex Deucher's suggestion
> - added i915
> 
> v4..v5:
> 
> - changed "include <linux/i2c.h>" to "struct i2c_adapter;"
> in drm_connector.h, consequently, added "include <linux/i2c.h>"
> in drm_sysfs.c.
> - added "drm_connector_init_with_ddc()" variant to ensure that the ddc
> field of drm_connector is preserved accross its invocation
> - accordingly changed invocations of drm_connector_init() in the
> touched drivers to use the new variant
> 
> v5..v6:
> 
> - improved subject line of patch 1
> - added kernel-doc for drm_connector_init_with_ddc()
> - improved kernel-doc for the ddc field of struct drm_connector
> - added Reviewed-by in patches 17 and 18
> - added Acked-by in patch 2
> - made the ownership of ddc i2c_adapter explicit in all patches,
> this made the affected patches much simpler
> 
> @Benjamin
> @Shawn
> 
> There were your Acked-by or Reviewed-by for some patches in v4, but now
> that the patches use the newly added function I'm not sure I can still
> include those tags without you actually confirming. Can I? Or can you
> please re-review? 
> 
> TODO: nouveau, gma500, omapdrm, panel-simple - if applicable.
> Other drivers are either already converted or don't mention neither
> "ddc" nor "i2c_adapter".
> 
Another way to check is to look for drm_get_edid. Sadly that also
highlights aux. dp/mst instances, which expose the DDC in another way.

For example comparing the diff stat wrt the following command shows
git grep -wc drm_get_edid -- drivers/gpu/drm/

> 
>  .../gpu/drm/amd/amdgpu/amdgpu_connectors.c    |  96 ++++++++----
drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c:1
- as pointed out by Alex - mix of aux dp/mst and normal

>  drivers/gpu/drm/ast/ast_mode.c                |  13 +-

drivers/gpu/drm/bridge/analogix-anx78xx.c:1
drivers/gpu/drm/bridge/analogix/analogix_dp_core.c:1
- not applicable: aux dp/mst


>  drivers/gpu/drm/bridge/dumb-vga-dac.c         |   6 +-

drivers/gpu/drm/bridge/sii902x.c:1
- normal instance(?) that should be updated at some point.

>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c     |   6 +-

drivers/gpu/drm/bridge/tc358767.c:1
- not applicable: aux dp/mst

>  drivers/gpu/drm/bridge/ti-tfp410.c            |   6 +-

drivers/gpu/drm/drm_dp_mst_topology.c:3
- not applicable: aux dp/mst

>  drivers/gpu/drm/drm_connector.c               |  35 +++++
>  drivers/gpu/drm/drm_sysfs.c                   |   8 +

drivers/gpu/drm/drm_edid.c:7
drivers/gpu/drm/drm_probe_helper.c:1
- unrelated

>  drivers/gpu/drm/exynos/exynos_hdmi.c          |   6 +-

drivers/gpu/drm/gma500/cdv_intel_dp.c:3
drivers/gpu/drm/gma500/cdv_intel_hdmi.c:2
drivers/gpu/drm/gma500/oaktrail_hdmi.c:1
drivers/gpu/drm/gma500/oaktrail_lvds.c:2
drivers/gpu/drm/gma500/psb_intel_modes.c:1
drivers/gpu/drm/gma500/psb_intel_sdvo.c:2
- should be updated at some point (as you pointed out).

>  drivers/gpu/drm/i915/display/intel_hdmi.c     |  12 +-
drivers/gpu/drm/i915/intel_connector.c:1
drivers/gpu/drm/i915/intel_crt.c:2
- not too sure here

drivers/gpu/drm/i915/intel_dp.c:2
- not applicable: aux dp/mst

drivers/gpu/drm/i915/intel_lvds.c:1
drivers/gpu/drm/i915/intel_sdvo.c:2
- not too sure here


>  drivers/gpu/drm/imx/imx-ldb.c                 |   7 +-
>  drivers/gpu/drm/imx/imx-tve.c                 |   6 +-
>  drivers/gpu/drm/mediatek/mtk_hdmi.c           |   7 +-
>  drivers/gpu/drm/mgag200/mgag200_mode.c        |  13 +-
>  drivers/gpu/drm/msm/hdmi/hdmi_connector.c     |   6 +-
drivers/gpu/drm/msm/edp/edp_ctrl.c:1
- not applicable: aux dp/mst

drivers/gpu/drm/nouveau/nouveau_connector.c:2
- should be updated at some point (as you pointed out).


drivers/gpu/drm/panel/panel-simple.c:1
- no applicable: panel driver


>  drivers/gpu/drm/radeon/radeon_connectors.c    | 142 +++++++++++++-----
>  drivers/gpu/drm/rockchip/inno_hdmi.c          |   6 +-
>  drivers/gpu/drm/rockchip/rk3066_hdmi.c        |   7 +-
>  drivers/gpu/drm/sti/sti_hdmi.c                |   6 +-
>  drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c        |   7 +-
>  drivers/gpu/drm/tegra/hdmi.c                  |   7 +-
>  drivers/gpu/drm/tegra/sor.c                   |   7 +-

drivers/gpu/drm/tegra/output.c:1
- already handled in hdmi/sor

>  drivers/gpu/drm/tilcdc/tilcdc_tfp410.c        |   6 +-
>  drivers/gpu/drm/vc4/vc4_hdmi.c                |  12 +-
>  drivers/gpu/drm/zte/zx_hdmi.c                 |   6 +-
>  drivers/gpu/drm/zte/zx_vga.c                  |   6 +-
>  include/drm/drm_connector.h                   |  18 +++
>  26 files changed, 336 insertions(+), 121 deletions(-)

In a Tl;Dr: I think this series covers 90%+ of the existing rather huge) driverset.

For the series:
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

Fwiw I'm in favour of Jani's suggestion to fold the dcc into the usual
helper drm_connector_init(). Although since we have 130+ instances it
might be better left for another day.

HTH
-Emil
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