[Intel-gfx] [PATCH] Check if the bus is valid prior to discovering edid.

[Adam Jackson]

On Thu, 2011-10-13 at 15:11 -0300, Eugeni Dodonov wrote:

> diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
> index d98cee6..b3a6eda 100644
> --- a/drivers/gpu/drm/i915/intel_i2c.c
> +++ b/drivers/gpu/drm/i915/intel_i2c.c
> @@ -470,3 +470,45 @@ void intel_teardown_gmbus(struct drm_device *dev)
>  	kfree(dev_priv->gmbus);
>  	dev_priv->gmbus = NULL;
>  }
> +
> +/**
> + * intel_drm_get_valid_edid - gets edid from existent adapters only
> + * @connector: DRM connector device to use
> + * @adapter: i2c adapter
> + *
> + * Verifies if the i2c adapter is responding to our queries before
> + * attempting to do proper communication with it. If it does,
> + * retreive the EDID with help of drm_get_edid
> + */
> +struct edid *
> +intel_drm_get_valid_edid(struct drm_connector *connector,
> +		struct i2c_adapter *adapter)
> +{
> +	int ret;
> +	u8 out_buf[] = { 0x0, 0x0};
> +	u8 buf[2];
> +	struct i2c_msg msgs[] = {
> +		{
> +			.addr = 0x50,
> +			.flags = 0,
> +			.len = 1,
> +			.buf = out_buf,
> +		},
> +		{
> +			.addr = 0x50,
> +			.flags = I2C_M_RD,
> +			.len = 1,
> +			.buf = buf,
> +		}
> +	};
> +
> +	/* We just check for -ENXIO - drm_get_edid checks if the transfer
> +	 * works and manages the remaining parts of the EDID */
> +	ret = i2c_transfer(adapter, msgs, 2);

This seems like it should be the implementation body of drm_probe_ddc,
and like that function should be EXPORT_SYMBOL()'d.  Other people want
to do zero-length reads too, you know.

- ajax
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