linux-kernel - Re: [PATCH 3/3] drm/bridge: fsl-ldb: simplify device

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Message-ID: <20250514230725.fmqnrxrr3odwzn4a@pengutronix.de>
Date: Thu, 15 May 2025 01:07:25 +0200
From: Marco Felsch <m.felsch@...gutronix.de>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: andrzej.hajda@...el.com, neil.armstrong@...aro.org, rfoss@...nel.org,
	jonas@...boo.se, jernej.skrabec@...il.com,
	maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
	tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	kernel@...gutronix.de
Subject: Re: [PATCH 3/3] drm/bridge: fsl-ldb: simplify device_node error
 handling

Hi Laurent,

On 25-05-15, Laurent Pinchart wrote:
> Hi Marco,
> 
> On Thu, May 15, 2025 at 12:24:53AM +0200, Marco Felsch wrote:
> > Make use of __free(device_node) to simplify the of_node_put() error
> > handling paths. No functional changes.
> > 
> > Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
> > ---
> >  drivers/gpu/drm/bridge/fsl-ldb.c | 24 +++++++++---------------
> >  1 file changed, 9 insertions(+), 15 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/bridge/fsl-ldb.c b/drivers/gpu/drm/bridge/fsl-ldb.c
> > index e0a229c91953..cea9ddaa5e01 100644
> > --- a/drivers/gpu/drm/bridge/fsl-ldb.c
> > +++ b/drivers/gpu/drm/bridge/fsl-ldb.c
> > @@ -287,8 +287,9 @@ 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;
> > -	struct device_node *remote1, *remote2;
> > +	struct device_node *panel_node __free(device_node) = NULL;
> > +	struct device_node *remote1 __free(device_node) = NULL;
> > +	struct device_node *remote2 __free(device_node) = NULL;
> >  	struct drm_panel *panel;
> >  	struct fsl_ldb *fsl_ldb;
> >  	int dual_link;
> > @@ -321,21 +322,16 @@ static int fsl_ldb_probe(struct platform_device *pdev)
> >  	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);
> > -	of_node_put(remote1);
> > -	of_node_put(remote2);
> > +	panel_node = remote1 ? remote1 : remote2;
> 
> This will cause a double put of panel_node, once due to __free() on
> remote1 or remote2, and the second time due to __free() on panel_node.

Argh.. you're right. I drop the __free() from the panel_node.

Thanks,
  Marco

> 
> >  
> > -	if (!fsl_ldb->ch0_enabled && !fsl_ldb->ch1_enabled) {
> > -		of_node_put(panel_node);
> > +	if (!fsl_ldb->ch0_enabled && !fsl_ldb->ch1_enabled)
> >  		return dev_err_probe(dev, -ENXIO, "No panel node found");
> > -	}
> >  
> >  	dev_dbg(dev, "Using %s\n",
> >  		fsl_ldb_is_dual(fsl_ldb) ? "dual-link mode" :
> >  		fsl_ldb->ch0_enabled ? "channel 0" : "channel 1");
> >  
> >  	panel = of_drm_find_panel(panel_node);
> > -	of_node_put(panel_node);
> >  	if (IS_ERR(panel))
> >  		return dev_err_probe(dev, PTR_ERR(panel), "drm panel not found\n");
> >  
> > @@ -345,14 +341,12 @@ static int fsl_ldb_probe(struct platform_device *pdev)
> >  				     "drm panel-bridge add failed\n");
> >  
> >  	if (fsl_ldb_is_dual(fsl_ldb)) {
> > -		struct device_node *port1, *port2;
> > +		struct device_node *port1 __free(device_node) =
> > +			of_graph_get_port_by_id(dev->of_node, 1);
> > +		struct device_node *port2 __free(device_node) =
> > +			of_graph_get_port_by_id(dev->of_node, 2);
> >  
> > -		port1 = of_graph_get_port_by_id(dev->of_node, 1);
> > -		port2 = of_graph_get_port_by_id(dev->of_node, 2);
> >  		dual_link = drm_of_lvds_get_dual_link_pixel_order(port1, port2);
> > -		of_node_put(port1);
> > -		of_node_put(port2);
> > -
> >  		if (dual_link < 0)
> >  			return dev_err_probe(dev, dual_link,
> >  					     "Error getting dual link configuration\n");
> 
> -- 
> Regards,
> 
> Laurent Pinchart
>