Re: [PATCH v4 14/34] drm/exynos: hdmi: remove the i2c drivers and use devtree

[Tomasz Figa <tomasz.figa@gmail.com>]

Hi,

On 30.01.2014 22:19, Sean Paul wrote:
> From: Daniel Kurtz <djkurtz@chromium.org>
>
> The i2c client was previously being passed into the hdmi driver via a
> dedicated i2c driver, and then a global variable. This patch removes all
> of that and just uses the device tree to get the i2c_client. This patch
> also properly references the client so we don't lose it before we're
> done with it.
>
> Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
> [seanpaul changed to phandle lookup instead of using of node name]
> Signed-off-by: Sean Paul <seanpaul@chromium.org>
> ---
>
> Changes in v2:
>   - Change include to linux/i2c.h instead of linux/of_i2c.h
> Changes in v3: None
> Changes in v4:
>   - Changed to find phy via phandle instead of by name
>
>   .../devicetree/bindings/video/exynos_hdmi.txt      |  5 ++
>   drivers/gpu/drm/exynos/Makefile                    |  1 -
>   drivers/gpu/drm/exynos/exynos_ddc.c                | 63 ---------------------
>   drivers/gpu/drm/exynos/exynos_hdmi.c               | 59 +++++++++-----------
>   drivers/gpu/drm/exynos/exynos_hdmi.h               | 23 --------
>   drivers/gpu/drm/exynos/exynos_hdmiphy.c            | 65 ----------------------
>   6 files changed, 32 insertions(+), 184 deletions(-)
>   delete mode 100644 drivers/gpu/drm/exynos/exynos_ddc.c
>   delete mode 100644 drivers/gpu/drm/exynos/exynos_hdmi.h
>   delete mode 100644 drivers/gpu/drm/exynos/exynos_hdmiphy.c
>
> diff --git a/Documentation/devicetree/bindings/video/exynos_hdmi.txt b/Documentation/devicetree/bindings/video/exynos_hdmi.txt
> index 50decf8..f9187a2 100644
> --- a/Documentation/devicetree/bindings/video/exynos_hdmi.txt
> +++ b/Documentation/devicetree/bindings/video/exynos_hdmi.txt
> @@ -25,6 +25,9 @@ Required properties:
>   		sclk_pixel.
>   - clock-names: aliases as per driver requirements for above clock IDs:
>   	"hdmi", "sclk_hdmi", "sclk_pixel", "sclk_hdmiphy" and "mout_hdmi".
> +- ddc: phandle to the hdmi ddc node
> +- phy: phandle to the hdmi phy node
> +

Adding new required properties to an already defined binding is breaking 
backwards compatibility, which is supposed to be preserved, since DT is 
an ABI.

Now, I'm not really a big fan of DT stability, but if we decide to 
maintain it for other Exynos drivers as well (e.g. USB), then we 
probably should do the same here...

Best regards,
Tomasz