Re: [PATCH v3 12/19] drm/mcde: dsi: don't create a panel_bridge

["Luca Ceresoli" <luca.ceresoli@bootlin.com>]

Hi Linus, Maxime,

On Tue Sep 22, 2026 at 9:09 AM CEST, Maxime Ripard wrote:
> On Wed, Sep 16, 2026 at 03:45:36PM +0200, Luca Ceresoli wrote:
>> Now a panel_bridge is automatically created for every drm_panel and the
>> panel-bridge API is just a deprecated wrapper to access it.
>>
>> Update and simplify the code by just getting a reference to the
>> already-existing bridge using of_drm_find_and_get_bridge().
>>
>> Also keep the "connected to non-panel bridge (unsupported)\n" error logic
>> by using the drm_bridge_is_panel() function.
>>
>> Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

[...]

>> @@ -1102,40 +1100,21 @@ static int mcde_dsi_bind(struct device *dev, struct device *master,
>>
>>  	/* Look for a panel as a child to this node */
>>  	for_each_available_child_of_node_scoped(dev->of_node, child) {
>> -		panel = of_drm_find_panel(child);
>> -		if (IS_ERR(panel)) {
>> -			dev_err(dev, "failed to find panel try bridge (%ld)\n",
>> -				PTR_ERR(panel));
>> -			panel = NULL;
>> -
>> -			bridge = of_drm_find_and_get_bridge(child);
>> -			if (!bridge) {
>> -				dev_err(dev, "failed to find bridge\n");
>> -				return -EINVAL;
>> -			}
>> +		bridge = of_drm_find_and_get_bridge(child);
>> +		if (!bridge) {
>> +			dev_err(dev, "failed to find bridge\n");
>> +			return -EINVAL;
>>  		}
>>
>> -		if (panel || bridge)
>> -			break;
>> +		break;
>>  	}
>> -	if (panel) {
>> -		bridge = drm_panel_bridge_add_typed(panel,
>> -						    DRM_MODE_CONNECTOR_DSI);
>> -		drm_panel_put(panel);
>> -		if (IS_ERR(bridge)) {
>> -			dev_err(dev, "error adding panel bridge\n");
>> -			return PTR_ERR(bridge);
>> -		}
>> -		drm_bridge_get(bridge);
>> -		dev_info(dev, "connected to panel\n");
>> -		d->panel = panel;
>> -	} else if (bridge) {
>> +	if (!bridge) {
>> +		dev_err(dev, "no bridge\n");
>> +		return -ENODEV;
>> +	} else if (!drm_bridge_is_panel(bridge)) {
>>  		/* TODO: AV8100 HDMI encoder goes here for example */
>>  		dev_info(dev, "connected to non-panel bridge (unsupported)\n");
>>  		return -ENODEV;
>
> I wonder if we still need that branch. Every panel is a bridge now, and
> it looks like we don't have any specific panel handling in this driver,
> so I guess it supports bridges already?
>
> Linus, do you know why this condition was here in the first place?

I had the same thought while writing the patch, but I chose to be
conservative.

Linus, unless you have more info I'm going to apply the patch as
is. Removing this special case would be welcome as a later patch.

Luca

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