drm/bridge: get/put the bridge returned by drm_bridge_get_last_bridge()

[PATCH 4/9] drm/omapdrm: use drm_bridge_chain_get_last_bridge()

Posted by Luca Ceresoli 7 months ago

Use drm_bridge_chain_get_last_bridge() instead of open coding a loop with
two invocations of drm_bridge_get_next_bridge() per iteration.

Besides being cleaner and more efficient, this change is necessary in
preparation for drm_bridge_get_next_bridge() to get a reference to the
returned bridge.

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
---
 drivers/gpu/drm/omapdrm/omap_drv.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
index 054b71dba6a75b8c42198c4b102a093f43a675a2..3bbcec01428a6f290afdfa40ef6f79629539a584 100644
--- a/drivers/gpu/drm/omapdrm/omap_drv.c
+++ b/drivers/gpu/drm/omapdrm/omap_drv.c
@@ -378,12 +378,12 @@ static int omap_display_id(struct omap_dss_device *output)
 	struct device_node *node = NULL;
 
 	if (output->bridge) {
-		struct drm_bridge *bridge = output->bridge;
-
-		while (drm_bridge_get_next_bridge(bridge))
-			bridge = drm_bridge_get_next_bridge(bridge);
+		struct drm_bridge *bridge =
+			drm_bridge_chain_get_last_bridge(output->bridge->encoder);
 
 		node = bridge->of_node;
+
+		drm_bridge_put(bridge);
 	}
 
 	return node ? of_alias_get_id(node, "display") : -ENODEV;

-- 
2.50.0

Re: [PATCH 4/9] drm/omapdrm: use drm_bridge_chain_get_last_bridge()

Posted by Maxime Ripard 7 months ago

On Wed, Jul 09, 2025 at 06:48:03PM +0200, Luca Ceresoli wrote:
> Use drm_bridge_chain_get_last_bridge() instead of open coding a loop with
> two invocations of drm_bridge_get_next_bridge() per iteration.
> 
> Besides being cleaner and more efficient, this change is necessary in
> preparation for drm_bridge_get_next_bridge() to get a reference to the
> returned bridge.
> 
> Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
> ---
>  drivers/gpu/drm/omapdrm/omap_drv.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
> index 054b71dba6a75b8c42198c4b102a093f43a675a2..3bbcec01428a6f290afdfa40ef6f79629539a584 100644
> --- a/drivers/gpu/drm/omapdrm/omap_drv.c
> +++ b/drivers/gpu/drm/omapdrm/omap_drv.c
> @@ -378,12 +378,12 @@ static int omap_display_id(struct omap_dss_device *output)
>  	struct device_node *node = NULL;
>  
>  	if (output->bridge) {
> -		struct drm_bridge *bridge = output->bridge;
> -
> -		while (drm_bridge_get_next_bridge(bridge))
> -			bridge = drm_bridge_get_next_bridge(bridge);
> +		struct drm_bridge *bridge =
> +			drm_bridge_chain_get_last_bridge(output->bridge->encoder);
>  
>  		node = bridge->of_node;
> +
> +		drm_bridge_put(bridge);

Any reason you're not using __free(drm_bridge_put) here?

Maxime

Re: [PATCH 4/9] drm/omapdrm: use drm_bridge_chain_get_last_bridge()

Posted by Luca Ceresoli 7 months ago

Hi Maxime,

On Thu, 10 Jul 2025 09:13:46 +0200
Maxime Ripard <mripard@kernel.org> wrote:

> On Wed, Jul 09, 2025 at 06:48:03PM +0200, Luca Ceresoli wrote:
> > Use drm_bridge_chain_get_last_bridge() instead of open coding a loop with
> > two invocations of drm_bridge_get_next_bridge() per iteration.
> > 
> > Besides being cleaner and more efficient, this change is necessary in
> > preparation for drm_bridge_get_next_bridge() to get a reference to the
> > returned bridge.
> > 
> > Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
> > ---
> >  drivers/gpu/drm/omapdrm/omap_drv.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
> > index 054b71dba6a75b8c42198c4b102a093f43a675a2..3bbcec01428a6f290afdfa40ef6f79629539a584 100644
> > --- a/drivers/gpu/drm/omapdrm/omap_drv.c
> > +++ b/drivers/gpu/drm/omapdrm/omap_drv.c
> > @@ -378,12 +378,12 @@ static int omap_display_id(struct omap_dss_device *output)
> >  	struct device_node *node = NULL;
> >  
> >  	if (output->bridge) {
> > -		struct drm_bridge *bridge = output->bridge;
> > -
> > -		while (drm_bridge_get_next_bridge(bridge))
> > -			bridge = drm_bridge_get_next_bridge(bridge);
> > +		struct drm_bridge *bridge =
> > +			drm_bridge_chain_get_last_bridge(output->bridge->encoder);
> >  
> >  		node = bridge->of_node;
> > +
> > +		drm_bridge_put(bridge);  
> 
> Any reason you're not using __free(drm_bridge_put) here?

Just because the code is simple enough that an explicit
drm_bridge_put() is clearly sufficient.

Do you think __free() should be used even in such trivial cases?

Luca

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

Re: [PATCH 4/9] drm/omapdrm: use drm_bridge_chain_get_last_bridge()

Posted by Maxime Ripard 6 months, 2 weeks ago

On Mon, Jul 14, 2025 at 12:32:40PM +0200, Luca Ceresoli wrote:
> Hi Maxime,
> 
> On Thu, 10 Jul 2025 09:13:46 +0200
> Maxime Ripard <mripard@kernel.org> wrote:
> 
> > On Wed, Jul 09, 2025 at 06:48:03PM +0200, Luca Ceresoli wrote:
> > > Use drm_bridge_chain_get_last_bridge() instead of open coding a loop with
> > > two invocations of drm_bridge_get_next_bridge() per iteration.
> > > 
> > > Besides being cleaner and more efficient, this change is necessary in
> > > preparation for drm_bridge_get_next_bridge() to get a reference to the
> > > returned bridge.
> > > 
> > > Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
> > > ---
> > >  drivers/gpu/drm/omapdrm/omap_drv.c | 8 ++++----
> > >  1 file changed, 4 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
> > > index 054b71dba6a75b8c42198c4b102a093f43a675a2..3bbcec01428a6f290afdfa40ef6f79629539a584 100644
> > > --- a/drivers/gpu/drm/omapdrm/omap_drv.c
> > > +++ b/drivers/gpu/drm/omapdrm/omap_drv.c
> > > @@ -378,12 +378,12 @@ static int omap_display_id(struct omap_dss_device *output)
> > >  	struct device_node *node = NULL;
> > >  
> > >  	if (output->bridge) {
> > > -		struct drm_bridge *bridge = output->bridge;
> > > -
> > > -		while (drm_bridge_get_next_bridge(bridge))
> > > -			bridge = drm_bridge_get_next_bridge(bridge);
> > > +		struct drm_bridge *bridge =
> > > +			drm_bridge_chain_get_last_bridge(output->bridge->encoder);
> > >  
> > >  		node = bridge->of_node;
> > > +
> > > +		drm_bridge_put(bridge);  
> > 
> > Any reason you're not using __free(drm_bridge_put) here?
> 
> Just because the code is simple enough that an explicit
> drm_bridge_put() is clearly sufficient.
> 
> Do you think __free() should be used even in such trivial cases?

It's a matter of opinion at this point :)

It' makes it a bit easier and consistent so that's why I raised it, but
if you feel like it's too much, that's fine by me as well.

Maxime

Re: [PATCH 4/9] drm/omapdrm: use drm_bridge_chain_get_last_bridge()

Posted by Luca Ceresoli 6 months, 1 week ago

Hi Maxime,

On Fri, 25 Jul 2025 16:15:23 +0200
Maxime Ripard <mripard@kernel.org> wrote:

> On Mon, Jul 14, 2025 at 12:32:40PM +0200, Luca Ceresoli wrote:
> > Hi Maxime,
> > 
> > On Thu, 10 Jul 2025 09:13:46 +0200
> > Maxime Ripard <mripard@kernel.org> wrote:
> >   
> > > On Wed, Jul 09, 2025 at 06:48:03PM +0200, Luca Ceresoli wrote:  
> > > > Use drm_bridge_chain_get_last_bridge() instead of open coding a loop with
> > > > two invocations of drm_bridge_get_next_bridge() per iteration.
> > > > 
> > > > Besides being cleaner and more efficient, this change is necessary in
> > > > preparation for drm_bridge_get_next_bridge() to get a reference to the
> > > > returned bridge.
> > > > 
> > > > Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
> > > > ---
> > > >  drivers/gpu/drm/omapdrm/omap_drv.c | 8 ++++----
> > > >  1 file changed, 4 insertions(+), 4 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
> > > > index 054b71dba6a75b8c42198c4b102a093f43a675a2..3bbcec01428a6f290afdfa40ef6f79629539a584 100644
> > > > --- a/drivers/gpu/drm/omapdrm/omap_drv.c
> > > > +++ b/drivers/gpu/drm/omapdrm/omap_drv.c
> > > > @@ -378,12 +378,12 @@ static int omap_display_id(struct omap_dss_device *output)
> > > >  	struct device_node *node = NULL;
> > > >  
> > > >  	if (output->bridge) {
> > > > -		struct drm_bridge *bridge = output->bridge;
> > > > -
> > > > -		while (drm_bridge_get_next_bridge(bridge))
> > > > -			bridge = drm_bridge_get_next_bridge(bridge);
> > > > +		struct drm_bridge *bridge =
> > > > +			drm_bridge_chain_get_last_bridge(output->bridge->encoder);
> > > >  
> > > >  		node = bridge->of_node;
> > > > +
> > > > +		drm_bridge_put(bridge);    
> > > 
> > > Any reason you're not using __free(drm_bridge_put) here?  
> > 
> > Just because the code is simple enough that an explicit
> > drm_bridge_put() is clearly sufficient.
> > 
> > Do you think __free() should be used even in such trivial cases?  
> 
> It's a matter of opinion at this point :)
> 
> It' makes it a bit easier and consistent so that's why I raised it, but
> if you feel like it's too much, that's fine by me as well.

In the end I chose to use __free here as well for v2, for consistency
over the series.

Luca

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