[PATCH v2] drm/mediatek/dp: fix mtk_dp_aux_transfer return value

[CK Hu (胡俊光)]

Hi, Wojciech:

On Wed, 2024-04-17 at 10:38 +0000, Wojciech Macek wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  In case there is no DP device attached to the port the
> transfer function should return IO error, similar to what
> other drivers do.
> In case EAGAIN is returned then any read from /dev/drm_dp_aux
> device ends up in an infinite loop as the upper layers
> constantly repeats the transfer request.

Reviewed-by: CK Hu <ck.hu at mediatek.com>

> 
> Fixes: f70ac097a2cf ("drm/mediatek: Add MT8195 Embedded DisplayPort
> driver")
> Signed-off-by: Wojciech Macek <wmacek at chromium.org>
> ---
> Changelog v2-v1:
>  - added "Fixes" tag
>  - corrected e-mail address
> 
> V1: 
> https://urldefense.com/v3/__https://patchwork.kernel.org/project/linux-mediatek/patch/20240402071113.3135903-1-wmacek@chromium.org/__;!!CTRNKA9wMg0ARbw!kBY_x5kGvdau3baCVwGwRuKojhHVIEW8Hvbw385x2pXi_1pCGMCntptpmOnEPoMbwA0dgA4JTxwfy6o$
>  
>  drivers/gpu/drm/mediatek/mtk_dp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c
> b/drivers/gpu/drm/mediatek/mtk_dp.c
> index 0ba72102636a..536366956447 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> @@ -2104,7 +2104,7 @@ static ssize_t mtk_dp_aux_transfer(struct
> drm_dp_aux *mtk_aux,
>  
>  	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP &&
>  	    !mtk_dp->train_info.cable_plugged_in) {
> -		ret = -EAGAIN;
> +		ret = -EIO;
>  		goto err;
>  	}
>