linux-kernel - Re: [PATCH v16 05/10] video: backlight: Add devres versions of of_find

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Date:   Thu, 18 Jan 2018 11:50:01 +0000
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Meghana Madhyastha <meghana.madhyastha@...il.com>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Noralf Trønnes <noralf@...nnes.org>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Sean Paul <seanpaul@...omium.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v16 05/10] video: backlight: Add devres versions of
 of_find_backlight

On Thu, Jan 18, 2018 at 04:32:26PM +0530, Meghana Madhyastha wrote:
> On Wed, Jan 17, 2018 at 05:09:57PM +0000, Daniel Thompson wrote:
> > On 16/01/18 10:34, Meghana Madhyastha wrote:
> > >Add devm_of_find_backlight and the corresponding release
> > >function because some drivers use devres versions of functions
> > >for acquiring device resources.
> > >
> > >Signed-off-by: Meghana Madhyastha <meghana.madhyastha@...il.com>
> > >---
> > >  drivers/video/backlight/backlight.c | 29 +++++++++++++++++++++++++++++
> > >  include/linux/backlight.h           |  7 +++++++
> > >  2 files changed, 36 insertions(+)
> > >
> > >diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> > >index 7e4a5d77d..b3f76945f 100644
> > >--- a/drivers/video/backlight/backlight.c
> > >+++ b/drivers/video/backlight/backlight.c
> > >@@ -620,6 +620,35 @@ struct backlight_device *of_find_backlight(struct device *dev)
> > >  }
> > >  EXPORT_SYMBOL(of_find_backlight);
> > >+static void devm_backlight_put(void *data)
> > >+{
> > >+	backlight_put(data);
> > 
> > Shouldn't this be using devres_release()?
> 
> backlight_put calls put_device which essentially does a release right?
> And looking at the code in other driver, looks like most of them use
> put_device (to the best of my knowledge, correct me if I'm mistaken). 

Sorry, the name confused me. I mistakenly though this was API code like
devm_gpiod_put and devm_clk_put, rather than a static method.

Whilst its my fault for overlooking the "static" please could rename this to
devm_backlight_release(). I don't want to keep being confused every time
I re-read it!


Daniel.

> 
> Thanks and regards,
> Meghana
> 
> > 
> > >+}
> > >+
> > >+/**
> > >+  * devm_of_find_backlight - Resource-managed of_find_backlight()
> > >+  * @dev: Device
> > >+  *
> > >+  * Device managed version of of_find_backlight(). The reference on the backlight
> > >+  * device is automatically dropped on driver detach.
> > >+  */
> > >+struct backlight_device *devm_of_find_backlight(struct device *dev)
> > >+{
> > >+	struct backlight_device *bd;
> > >+	int ret;
> > >+
> > >+	bd = of_find_backlight(dev);
> > >+	if (IS_ERR_OR_NULL(bd))
> > >+		return bd;
> > >+	ret = devm_add_action(dev, devm_backlight_put, bd);
> > >+	if (ret) {
> > >+		backlight_put(bd);
> > >+		return ERR_PTR(ret);
> > >+	}
> > >+	return bd;
> > >+}
> > >+EXPORT_SYMBOL(devm_of_find_backlight);
> > >+
> > >  static void __exit backlight_class_exit(void)
> > >  {
> > >  	class_destroy(backlight_class);
> > >diff --git a/include/linux/backlight.h b/include/linux/backlight.h
> > >index 32ea510da..1d373f5a6 100644
> > >--- a/include/linux/backlight.h
> > >+++ b/include/linux/backlight.h
> > >@@ -215,11 +215,18 @@ of_find_backlight_by_node(struct device_node *node)
> > >  #if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
> > >  struct backlight_device *of_find_backlight(struct device *dev);
> > >+struct backlight_device *devm_of_find_backlight(struct device *dev);
> > >  #else
> > >  static inline struct backlight_device *of_find_backlight(struct device *dev)
> > >  {
> > >  	return NULL;
> > >  }
> > >+
> > >+static inline struct backlight_device *
> > >+devm_of_find_backlight(struct device *dev)
> > >+{
> > >+	return NULL;
> > >+}
> > >  #endif
> > >  #endif
> > >