[Intel-gfx] [PATCH] drm/i915/dp: return number of bytes written for short aux/i2c writes

[Ville Syrjälä]

On Tue, Mar 17, 2015 at 05:18:54PM +0200, Jani Nikula wrote:
> Allow for a larger receive data size, and check if the receiver returned
> the number of bytes written. Without this, we've basically skipped all
> the unwritten bytes for short writes.
> 
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>

Whoops :)

Looks correct to me.

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

> ---
>  drivers/gpu/drm/i915/intel_dp.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 5256c064da05..3967af10f53c 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -951,7 +951,7 @@ intel_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
>  	case DP_AUX_NATIVE_WRITE:
>  	case DP_AUX_I2C_WRITE:
>  		txsize = msg->size ? HEADER_SIZE + msg->size : BARE_ADDRESS_SIZE;
> -		rxsize = 1;
> +		rxsize = 2; /* 0 or 1 data bytes */
>  
>  		if (WARN_ON(txsize > 20))
>  			return -E2BIG;
> @@ -962,8 +962,13 @@ intel_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
>  		if (ret > 0) {
>  			msg->reply = rxbuf[0] >> 4;
>  
> -			/* Return payload size. */
> -			ret = msg->size;
> +			if (ret > 1) {
> +				/* Number of bytes written in a short write. */
> +				ret = clamp_t(int, rxbuf[1], 0, msg->size);
> +			} else {
> +				/* Return payload size. */
> +				ret = msg->size;
> +			}
>  		}
>  		break;
>  
> -- 
> 2.1.4

-- 
Ville Syrjälä
Intel OTC