[PATCH] drm/bridge: waveshare-dsi: Register and attach our DSI device at probe

[PATCH] drm/bridge: waveshare-dsi: Register and attach our DSI device at probe

[Marek Vasut]

In order to avoid any probe ordering issue, the best practice is to move
the secondary MIPI-DSI device registration and attachment to the
MIPI-DSI host at probe time.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
---
Note that this is similar to e.g. commit
6ef7ee48765f ("drm/bridge: sn65dsi83: Register and attach our DSI device at probe")
and pretty much what every other DSI-to-DPI bridge does.
---
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
Cc: Jonas Karlman <jonas@kwiboo.se>
Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Neil Armstrong <neil.armstrong@linaro.org>
Cc: Robert Foss <rfoss@kernel.org>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org
---
 drivers/gpu/drm/bridge/waveshare-dsi.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/waveshare-dsi.c b/drivers/gpu/drm/bridge/waveshare-dsi.c
index 43f4e7412d722..9254446f54958 100644
--- a/drivers/gpu/drm/bridge/waveshare-dsi.c
+++ b/drivers/gpu/drm/bridge/waveshare-dsi.c
@@ -80,11 +80,6 @@ static int ws_bridge_bridge_attach(struct drm_bridge *bridge,
 				   enum drm_bridge_attach_flags flags)
 {
 	struct ws_bridge *ws = bridge_to_ws_bridge(bridge);
-	int ret;
-
-	ret = ws_bridge_attach_dsi(ws);
-	if (ret)
-		return ret;
 
 	return drm_bridge_attach(encoder, ws->next_bridge,
 				 &ws->bridge, flags);
@@ -179,7 +174,7 @@ static int ws_bridge_probe(struct i2c_client *i2c)
 	ws->bridge.of_node = dev->of_node;
 	devm_drm_bridge_add(dev, &ws->bridge);
 
-	return 0;
+	return ws_bridge_attach_dsi(ws);
 }
 
 static const struct of_device_id ws_bridge_of_ids[] = {
-- 
2.51.0

Re: [PATCH] drm/bridge: waveshare-dsi: Register and attach our DSI device at probe

[Marek Vasut]

On 1/13/26 12:47 AM, Marek Vasut wrote:
> In order to avoid any probe ordering issue, the best practice is to move
> the secondary MIPI-DSI device registration and attachment to the
> MIPI-DSI host at probe time.
> 
> Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
> ---
> Note that this is similar to e.g. commit
> 6ef7ee48765f ("drm/bridge: sn65dsi83: Register and attach our DSI device at probe")
> and pretty much what every other DSI-to-DPI bridge does.
> ---
> Cc: Andrzej Hajda <andrzej.hajda@intel.com>
> Cc: David Airlie <airlied@gmail.com>
> Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
> Cc: Jonas Karlman <jonas@kwiboo.se>
> Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Neil Armstrong <neil.armstrong@linaro.org>
> Cc: Robert Foss <rfoss@kernel.org>
> Cc: Simona Vetter <simona@ffwll.ch>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: dri-devel@lists.freedesktop.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-renesas-soc@vger.kernel.org
> ---
>   drivers/gpu/drm/bridge/waveshare-dsi.c | 7 +------
>   1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/waveshare-dsi.c b/drivers/gpu/drm/bridge/waveshare-dsi.c
> index 43f4e7412d722..9254446f54958 100644
> --- a/drivers/gpu/drm/bridge/waveshare-dsi.c
> +++ b/drivers/gpu/drm/bridge/waveshare-dsi.c
> @@ -80,11 +80,6 @@ static int ws_bridge_bridge_attach(struct drm_bridge *bridge,
>   				   enum drm_bridge_attach_flags flags)
>   {
>   	struct ws_bridge *ws = bridge_to_ws_bridge(bridge);
> -	int ret;
> -
> -	ret = ws_bridge_attach_dsi(ws);
> -	if (ret)
> -		return ret;
>   
>   	return drm_bridge_attach(encoder, ws->next_bridge,
>   				 &ws->bridge, flags);
> @@ -179,7 +174,7 @@ static int ws_bridge_probe(struct i2c_client *i2c)
>   	ws->bridge.of_node = dev->of_node;
>   	devm_drm_bridge_add(dev, &ws->bridge);
>   
> -	return 0;
> +	return ws_bridge_attach_dsi(ws);
>   }
>   
>   static const struct of_device_id ws_bridge_of_ids[] = {

Is there anything that should be done with this patch ?

Re: [PATCH] drm/bridge: waveshare-dsi: Register and attach our DSI device at probe

[Luca Ceresoli]

Hello Marek,

On Tue Jan 13, 2026 at 12:47 AM CET, Marek Vasut wrote:
> In order to avoid any probe ordering issue, the best practice is to move
> the secondary MIPI-DSI device registration and attachment to the
> MIPI-DSI host at probe time.
>
> Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>

Hadn't seen this patch initially, but it caught my attention now.

> Note that this is similar to e.g. commit
> 6ef7ee48765f ("drm/bridge: sn65dsi83: Register and attach our DSI device at probe")
> and pretty much what every other DSI-to-DPI bridge does.

Digression:

  Looking at 6ef7ee48765f, I now realize it has removed one obstacle to the
  DRM bridge hotplug which I'm working to achieve. For the interested,
  there would be one more issue in addition to those I discussed in [0]
  without that commit.

  [0] https://lore.kernel.org/lkml/DE2LCFM56Z2Y.2V9NIXP26QOM2@bootlin.com/

Back to your patch, I don't have the hardware but LGTM and I'm not aware of
any issues it might cause. Still it would be good if you could describe
what goes wrong with current code.

Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [PATCH] drm/bridge: waveshare-dsi: Register and attach our DSI device at probe

[Marek Vasut]

On 2/6/26 9:18 AM, Luca Ceresoli wrote:

Hello Luca,

> Back to your patch, I don't have the hardware but LGTM and I'm not aware of
> any issues it might cause. Still it would be good if you could describe
> what goes wrong with current code.
> 
> Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

Let me send a V2 with issue description.

-- 
Best regards,
Marek Vasut