[PATCH] drm/amd/display: fix return value of dm_dp_aux_transfer() (V2)

[Harry Wentland]

On 2018-04-17 10:56 PM, Shirish S wrote:
> Currently the dm_dp_aux_transfer() does not parse
> the return value of dal_ddc_service_read_dpcd_data(), which also
> has a failure case.
> This patch captures the same and ensures the i2c operation status is
> sent appropriately to the drm framework.
> 
> V2: Updated commit message.
> 
> Signed-off-by: Shirish S <shirish.s at amd.com>
> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> index 782491e..7ac124d 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> @@ -115,7 +115,11 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
>  				msg->address,
>  				msg->buffer,
>  				msg->size);
> -		return read_bytes;
> +		if (read_bytes != msg->size &&
> +		    read_bytes >= DDC_RESULT_FAILED_OPERATION)

This doesn't look right. We shouldn't be returning the size or error code from the same function. This will not work if we submit a read 7 or 8 bytes and get an error.

Harry

> +			return -EIO;
> +		else
> +			return read_bytes;
>  	case DP_AUX_I2C_WRITE:
>  		res = dal_ddc_service_write_dpcd_data(
>  				TO_DM_AUX(aux)->ddc_service,
>