[PATCH v10 2/9] drm/bridge: fsl-ldb: Get the next non-panel bridge

[Luca Ceresoli]

Hello Laurentiu,

> The next bridge in bridge chain could be a panel bridge or a non-panel
> bridge.  Use devm_drm_of_get_bridge() to replace the combination
> function calls of of_drm_find_panel() and devm_drm_panel_bridge_add()
> to get either a panel bridge or a non-panel bridge, instead of getting
> a panel bridge only.

Since commit b7797081ccfe ("drm/panel: embed a drm_bridge into every
drm_panel") there is no such thing as a panel_bridge. Now every panel just
embeds a bridge, and there is no reason to use the panel_bridge API. All
bridges/encoders/whoever needing to interact with "the next component, be
it a bridge or a panel" should just use the bridge API.

The old panel_bridge APIs are deprecated [0] and by now they are just
complicated wrappers to the bridge API.

I'm addressing the conversion to bridge API and eventual removal of the
deprecated panel_bridge API as time permits (but pathces would be
welcome). This driver has already been converted by commit 802372cf316a
("drm/bridge: fsl-ldb: don't create a panel_bridge"), so this patch is
basically not changing anything: it's still getting a pointer to the next
bridge, but switches to a slightly more complicated implementation.

So I'd drop this patch.

Still it's good to get rid of the obsolete "panel" wording because now we
don't interact with a panel aymore, see below.

[0] https://gitlab.freedesktop.org/drm/misc/kernel/-/blob/drm-misc-next/Documentation/gpu/todo.rst#remove-panel_bridge-api-functions

>
> Signed-off-by: Liu Ying <victor.liu at nxp.com>
> Signed-off-by: Laurentiu Palcu <laurentiu.palcu at oss.nxp.com>
>
> diff --git a/drivers/gpu/drm/bridge/fsl-ldb.c b/drivers/gpu/drm/bridge/fsl-ldb.c
> index 7ec84c81cd78..52ae7f5b63c7 100644
> --- a/drivers/gpu/drm/bridge/fsl-ldb.c
> +++ b/drivers/gpu/drm/bridge/fsl-ldb.c
> @@ -294,8 +294,8 @@ static const struct drm_bridge_funcs funcs = {
>  static int fsl_ldb_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> -	struct device_node *panel_node;

This could be renamed remote_bridge, or next_bridge_node, or the like.

>  	struct device_node *remote1, *remote2;
> +	struct drm_bridge *next_bridge;
>  	struct fsl_ldb *fsl_ldb;
>  	int dual_link;
>
> @@ -318,19 +318,16 @@ static int fsl_ldb_probe(struct platform_device *pdev)
>  	if (IS_ERR(fsl_ldb->regmap))
>  		return PTR_ERR(fsl_ldb->regmap);
>
> -	/* Locate the remote ports and the panel node */
> +	/* Locate the remote ports. */

This is OK.

>  	remote1 = of_graph_get_remote_node(dev->of_node, 1, 0);
>  	remote2 = of_graph_get_remote_node(dev->of_node, 2, 0);
>  	fsl_ldb->ch0_enabled = (remote1 != NULL);
>  	fsl_ldb->ch1_enabled = (remote2 != NULL);
> -	panel_node = of_node_get(remote1 ? remote1 : remote2);

I'd leave it as is, it's just less code (and more efficient FWIW)
than... see below (*)

>  	of_node_put(remote1);
>  	of_node_put(remote2);
>
> -	if (!fsl_ldb->ch0_enabled && !fsl_ldb->ch1_enabled) {
> -		of_node_put(panel_node);
> -		return dev_err_probe(dev, -ENXIO, "No panel node found");
> -	}
> +	if (!fsl_ldb->ch0_enabled && !fsl_ldb->ch1_enabled)
> +		return dev_err_probe(dev, -ENXIO, "No next bridge node found");

This can be simplified by using a clenaup action on panel_node (or whatever
the new name will be), so the of_node_put() would disappear. See for
example commit 23bc92902edd ("drm/mxsfb/lcdif: simplify ep pointer
management using __free").


> @@ -339,10 +336,14 @@ static int fsl_ldb_probe(struct platform_device *pdev)
>  	if (of_property_present(dev->of_node, "nxp,enable-termination-resistor"))
>  		fsl_ldb->use_termination_resistor = true;
>
> -	fsl_ldb->bridge.next_bridge = of_drm_find_and_get_bridge(panel_node);
> -	of_node_put(panel_node);
> -	if (!fsl_ldb->bridge.next_bridge)
> -		return -ENODEV;
> +	next_bridge = of_drm_get_bridge_by_endpoint(dev->of_node,
> +						    fsl_ldb->ch0_enabled ? 1 : 2,
> +						    0);

(*) ...this code.

> +	if (IS_ERR(next_bridge))
> +		return dev_err_probe(dev, PTR_ERR(next_bridge),
> +				     "failed to get next bridge\n");
> +
> +	fsl_ldb->bridge.next_bridge = next_bridge;
>
>  	if (fsl_ldb_is_dual(fsl_ldb)) {
>  		struct device_node *port1, *port2;

Luca

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