[PATCH v2] i2c: of: Try to find an I2C adapter matching the parent

[Tristan Bastian]

Am 25.01.19 um 14:11 schrieb Thierry Reding:
> From: Thierry Reding <treding at nvidia.com>
>
> If an I2C adapter doesn't match the provided device tree node, also try
> matching the parent's device tree node. This allows finding an adapter
> based on the device node of the parent device that was used to register
> it.
>
> This fixes a regression on Tegra124-based Chromebooks (Nyan) where the
> eDP controller registers an I2C adapter that is used to read to EDID.
> After commit 993a815dcbb2 ("dt-bindings: panel: Add missing .txt
> suffix") this stopped working because the I2C adapter could no longer
> be found. The approach in this patch fixes the regression without
> introducing the issues that the above commit solved.
>
> Fixes: 17ab7806de0c ("drm: don't link DP aux i2c adapter to the hardware device node")
> Signed-off-by: Thierry Reding <treding at nvidia.com>
> ---
> Changes in v2:
> - check for both device and parent device tree nodes for each device
>    instead of looping through the list of devices twice
>
>   drivers/i2c/i2c-core-of.c | 14 +++++++++++++-
>   1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/i2c-core-of.c b/drivers/i2c/i2c-core-of.c
> index 6cb7ad608bcd..0f01cdba9d2c 100644
> --- a/drivers/i2c/i2c-core-of.c
> +++ b/drivers/i2c/i2c-core-of.c
> @@ -121,6 +121,17 @@ static int of_dev_node_match(struct device *dev, void *data)
>   	return dev->of_node == data;
>   }
>   
> +static int of_dev_or_parent_node_match(struct device *dev, void *data)
> +{
> +	if (dev->of_node == data)
> +		return 1;
> +
> +	if (dev->parent)
> +		return dev->parent->of_node == data;
> +
> +	return 0;
> +}
> +
>   /* must call put_device() when done with returned i2c_client device */
>   struct i2c_client *of_find_i2c_device_by_node(struct device_node *node)
>   {
> @@ -145,7 +156,8 @@ struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node)
>   	struct device *dev;
>   	struct i2c_adapter *adapter;
>   
> -	dev = bus_find_device(&i2c_bus_type, NULL, node, of_dev_node_match);
> +	dev = bus_find_device(&i2c_bus_type, NULL, node,
> +			      of_dev_or_parent_node_match);
>   	if (!dev)
>   		return NULL;
>   

I've tested this and can confirm that this fixes the issue on the 
nyan-big chromebook.
Is this fix going to be applied to the LTS kernels too?

Thanks.