Re: [PATCH v1 1/1] drm/mediatek: Add return value check when reading DPCD

["CK Hu (胡俊光)" <ck.hu@mediatek.com>]

Hi, Liankun:

On Mon, 2024-09-30 at 17:17 +0800, Liankun Yang wrote:
> Returns the number of bytes transferred (1) on success.
> Check the return value to confirm that AUX communication is successful.
> 
> Fixes: f70ac097a2cf ("drm/mediatek: Add MT8195 Embedded DisplayPort driver")

Fixes: d9e6ea02fc3f ("drm/mediatek: dp: Add MT8195 External DisplayPort support")

Regards,
CK

> 
> Signed-off-by: Liankun Yang <liankun.yang@mediatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dp.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
> index d8796a904eca..3cab65345d1e 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> @@ -2018,6 +2018,7 @@ static enum drm_connector_status mtk_dp_bdg_detect(struct drm_bridge *bridge)
>  	enum drm_connector_status ret = connector_status_disconnected;
>  	bool enabled = mtk_dp->enabled;
>  	u8 sink_count = 0;
> +	size_t value;
>  
>  	if (!mtk_dp->train_info.cable_plugged_in)
>  		return ret;
> @@ -2032,7 +2033,12 @@ static enum drm_connector_status mtk_dp_bdg_detect(struct drm_bridge *bridge)
>  	 * function, we just need to check the HPD connection to check
>  	 * whether we connect to a sink device.
>  	 */
> -	drm_dp_dpcd_readb(&mtk_dp->aux, DP_SINK_COUNT, &sink_count);
> +	value = drm_dp_dpcd_readb(&mtk_dp->aux, DP_SINK_COUNT, &sink_count);
> +	if (value < 0) {
> +		drm_err(mtk_dp->drm_dev, "Failed to read DP Sink Count: %zd\n", value);
> +		return ret;
> +	}
> +
>  	if (DP_GET_SINK_COUNT(sink_count))
>  		ret = connector_status_connected;
>