Messages in this thread | | | Date | Fri, 30 Apr 2021 20:40:15 +0530 | From | rajeevny@codeauro ... | Subject | Re: [v3 1/2] dt-bindings: backlight: add DisplayPort aux backlight |
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On 30-04-2021 02:33, Doug Anderson wrote: > Hi, > > On Thu, Apr 29, 2021 at 11:04 AM Rob Herring <robh@kernel.org> wrote: >> >> On Mon, Apr 26, 2021 at 11:29:15AM +0530, Rajeev Nandan wrote: >> > Add bindings for DisplayPort aux backlight driver. >> > >> > Changes in v2: >> > - New >> > >> > Signed-off-by: Rajeev Nandan <rajeevny@codeaurora.org> >> > --- >> > .../bindings/leds/backlight/dp-aux-backlight.yaml | 49 ++++++++++++++++++++++ >> > 1 file changed, 49 insertions(+) >> > create mode 100644 Documentation/devicetree/bindings/leds/backlight/dp-aux-backlight.yaml >> > >> > diff --git a/Documentation/devicetree/bindings/leds/backlight/dp-aux-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/dp-aux-backlight.yaml >> > new file mode 100644 >> > index 00000000..0fa8bf0 >> > --- /dev/null >> > +++ b/Documentation/devicetree/bindings/leds/backlight/dp-aux-backlight.yaml >> > @@ -0,0 +1,49 @@ >> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) >> > +%YAML 1.2 >> > +--- >> > +$id: http://devicetree.org/schemas/leds/backlight/dp-aux-backlight.yaml# >> > +$schema: http://devicetree.org/meta-schemas/core.yaml# >> > + >> > +title: DisplayPort aux backlight driver bindings >> > + >> > +maintainers: >> > + - Rajeev Nandan <rajeevny@codeaurora.org> >> > + >> > +description: >> > + Backlight driver to control the brightness over DisplayPort aux channel. >> > + >> > +allOf: >> > + - $ref: common.yaml# >> > + >> > +properties: >> > + compatible: >> > + const: dp-aux-backlight >> > + >> > + ddc-i2c-bus: >> > + $ref: /schemas/types.yaml#/definitions/phandle >> > + description: >> > + A phandle to the system I2C controller connected to the DDC bus used >> > + for the DisplayPort AUX channel. >> > + >> > + enable-gpios: >> > + maxItems: 1 >> > + description: GPIO specifier for backlight enable pin. >> > + >> > + max-brightness: true >> > + >> > +required: >> > + - compatible >> > + - ddc-i2c-bus >> > + >> > +additionalProperties: false >> > + >> > +examples: >> > + - | >> > + backlight { >> > + compatible = "dp-aux-backlight"; >> > + ddc-i2c-bus = <&sn65dsi86_bridge>; >> > + enable-gpios = <&tlmm 12 GPIO_ACTIVE_HIGH>; >> >> So the DDC bus is connected to a backlight and also a panel? This >> binding is not reflecting the h/w, but rather what you want for some >> driver. >> >> There's only one thing here and that's an eDP panel which supports >> backlight control via DP aux channel. You can figure all that out from >> the panel's compatible and/or reading the EDID. >> >> You might also be interested in this thread: >> >> https://lore.kernel.org/lkml/YIKsDtjcIHGNvW0u@orome.fritz.box/ > > I think Rajeev needs to rework everything anyway as per: > > https://lore.kernel.org/r/87zgxl5qar.fsf@intel.com > > ...but you're right that it makes sense not to model the backlight as > a separate node in the device tree. The panel driver can handle > setting up the backlight. > > -Doug
It was not a good idea to create a separate backlight driver and use ddc-i2c-bus to get access to DP aux. I am working to move the code to the panel driver and to utilize the new DRM helper functions (drm_edp_backlight_*) Lyude has added [1].
To use these helper functions, the panel driver should have access to the "struct drm_dp_aux *". The simple-panel has a "ddc-i2c-bus" property to give the panel access to the DDC bus and is currently being used to get the EDID from the panel. Can I use the same ddc bus i2c_adapter to get the "struct drm_dp_aux *"?
As per the suggestion [2], I get the "struct drm_dp_aux *" from the i2c_adapter of ddc bus (maybe I didn't understand the suggestion correctly), and, it turned out, the way I have implemented is not the right way [3]. So, I am afraid to use the same method in the panel driver.
[1] https://lore.kernel.org/dri-devel/871rb5bcf9.fsf@intel.com/ [2] https://www.spinics.net/lists/dri-devel/msg295429.html [3] https://lore.kernel.org/dri-devel/20210426111116.4lc3ekxjugjr3oho@maple.lan/
Thanks, Rajeev
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