linux-kernel - Re: [PATCH v3 1/1] drm/mediatek: Add return value check when reading DPCD

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Message-ID: <CABnWg9uvQ4_vxYx-_8AKE_CvLgKd04LuvS1qvKwyMHvBck7_cw@mail.gmail.com>
Date: Thu, 19 Dec 2024 03:51:16 -0600
From: Guillaume Ranquet <granquet@...libre.com>
To: Liankun Yang <liankun.yang@...iatek.com>, chunkuang.hu@...nel.org, 
	p.zabel@...gutronix.de, airlied@...il.com, simona@...ll.ch, 
	matthias.bgg@...il.com, angelogioacchino.delregno@...labora.com, 
	ck.hu@...iatek.com, dmitry.osipenko@...labora.com, rex-bc.chen@...iatek.com, 
	jitao.shi@...iatek.com, mac.shen@...iatek.com, peng.liu@...iatek.com, 
	Project_Global_Chrome_Upstream_Group@...iatek.com
Cc: dri-devel@...ts.freedesktop.org, linux-mediatek@...ts.infradead.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] drm/mediatek: Add return value check when reading DPCD

On Wed, 18 Dec 2024 12:34, Liankun Yang <liankun.yang@...iatek.com> wrote:
>Returns the number of bytes transferred (1) on success.
Hi Liankun,

I'm not sure this statement above is true, you are not returning the
number of transferred bytes?


Aside of that little nitpick

Reviewed-by: Guillaume Ranquet <granquet@...libre.com>

>Check the return value to confirm that AUX communication is successful.
>
>Fixes: f70ac097a2cf ("drm/mediatek: Add MT8195 Embedded DisplayPort driver")
>
>Signed-off-by: Liankun Yang <liankun.yang@...iatek.com>
>---
>Changes in V3:
>- Using drm_dp_read_sink_count() to improve patch.
>Per suggestion from the previous thread:
>https://patchwork.kernel.org/project/linux-mediatek/patch/20241128030940.25657-1-liankun.yang@mediatek.com/
>
>Changes in V2:
>- Modify Fixes in Commit Message.
>Per suggestion from the previous thread:
>https://patchwork.kernel.org/project/linux-mediatek/patch/20240930092000.5385-1-liankun.yang@mediatek.com/
>---
> drivers/gpu/drm/mediatek/mtk_dp.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
>index 36713c176cfc..b26dad8783be 100644
>--- a/drivers/gpu/drm/mediatek/mtk_dp.c
>+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
>@@ -2100,7 +2100,6 @@ static enum drm_connector_status mtk_dp_bdg_detect(struct drm_bridge *bridge)
> 	struct mtk_dp *mtk_dp = mtk_dp_from_bridge(bridge);
> 	enum drm_connector_status ret = connector_status_disconnected;
> 	bool enabled = mtk_dp->enabled;
>-	u8 sink_count = 0;
>
> 	if (!mtk_dp->train_info.cable_plugged_in)
> 		return ret;
>@@ -2115,8 +2114,8 @@ 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);
>-	if (DP_GET_SINK_COUNT(sink_count))
>+
>+	if (drm_dp_read_sink_count(&mtk_dp->aux))
> 		ret = connector_status_connected;
>
> 	if (!enabled)
>--
>2.45.2