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

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Date:   Thu, 18 Jan 2018 16:32:26 +0530
From:   Meghana Madhyastha <meghana.madhyastha@...il.com>
To:     Daniel Thompson <daniel.thompson@...aro.org>,
        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 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). 

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
> >