linux-kernel - Re: [PATCH] pwm: add devm_pwm_get() and devm_pwm

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Message-ID: <20120801080453.GJ29673@avionic-0098.adnet.avionic-design.de>
Date:	Wed, 1 Aug 2012 10:04:53 +0200
From:	Thierry Reding <thierry.reding@...onic-design.de>
To:	Alexandre Courbot <acourbot@...dia.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pwm: add devm_pwm_get() and devm_pwm_put()

On Wed, Aug 01, 2012 at 04:37:09PM +0900, Alexandre Courbot wrote:
> Add resource managed variants of pwm_get() and pwm_put() for
> convenience. Code is largely inspired by the equivalent devm functions
> of the regulator framework.
> 
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> ---
>  Documentation/driver-model/devres.txt |  4 +++
>  Documentation/pwm.txt                 |  5 +--
>  drivers/pwm/core.c                    | 57 +++++++++++++++++++++++++++++++++++
>  include/linux/pwm.h                   |  3 ++
>  4 files changed, 67 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt
> index 950856b..43cff70 100644
> --- a/Documentation/driver-model/devres.txt
> +++ b/Documentation/driver-model/devres.txt
> @@ -284,3 +284,7 @@ CLOCK
>  PINCTRL
>    devm_pinctrl_get()
>    devm_pinctrl_put()
> +
> +PWM
> +  devm_pwm_get()
> +  devm_pwm_put()
> diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
> index 554290e..4719c12 100644
> --- a/Documentation/pwm.txt
> +++ b/Documentation/pwm.txt
> @@ -35,8 +35,9 @@ Using PWMs
>  Legacy users can request a PWM device using pwm_request() and free it
>  after usage with pwm_free().
>  
> -New users should use the pwm_get() function and pass to it the consumer
> -device or a consumer name. pwm_put() is used to free the PWM device.
> +New users should use the pwm_get() or devm_pwm_get() function and pass to it the
> +consumer device or a consumer name. pwm_put() or devm_pwm_put() is used to free
> +the PWM device.

I think I'd prefer the original text with an additional line mentioning
the managed variants.

>  
>  After being requested a PWM has to be configured using:
>  
> diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> index ecb7690..5a5e19b 100644
> --- a/drivers/pwm/core.c
> +++ b/drivers/pwm/core.c
> @@ -624,6 +624,63 @@ out:
>  }
>  EXPORT_SYMBOL_GPL(pwm_put);
>  
> +static void devm_pwm_release(struct device *dev, void *res)
> +{
> +	pwm_put(*(struct pwm_device **)res);
> +}
> +
> +/**
> + * devm_pwm_get() - Resource managed pwm_get()

This is missing parameter descriptions here.

> + *
> + * This works are pwm_get() but the acquired pwm will automatically be released

"works like"? Also "acquired PWM" or "acquired PWM device".

> + * on driver detach. See pwm_get() for more details.
> + */
> +struct pwm_device *devm_pwm_get(struct device *dev, const char *consumer)
> +{
> +	struct pwm_device **ptr, *pwm;
> +
> +	ptr = devres_alloc(devm_pwm_release, sizeof(**ptr), GFP_KERNEL);
> +	if (!ptr)
> +		return ERR_PTR(-ENOMEM);
> +
> +	pwm = pwm_get(dev, consumer);
> +	if (!IS_ERR(pwm)) {
> +		*ptr = pwm;
> +		devres_add(dev, ptr);
> +	} else {
> +		devres_free(ptr);
> +	}
> +
> +	return pwm;
> +}
> +EXPORT_SYMBOL_GPL(devm_pwm_get);
> +
> +static int devm_pwm_match(struct device *dev, void *res, void *data)
> +{
> +	struct pwm_device **p = res;
> +
> +	if (WARN_ON(!p || !*p))
> +		return 0;
> +
> +	return *p == data;
> +}
> +
> +/**
> + * devm_pwm_put() - Resource managed pwm_put()
> + *
> + * Releases a pwm previously allocated using devm_pwm_get. Calling this function
> + * is usually not needed as the devm-allocated pwm will automatically be
> + * released on driver detach.
> + */

Same comments as for devm_pwm_get().

> +void devm_pwm_put(struct device *dev, struct pwm_device *pwm)
> +{
> +	int ret;
> +
> +	ret = devres_release(dev, devm_pwm_release, devm_pwm_match, pwm);
> +	WARN_ON(ret);
> +}
> +EXPORT_SYMBOL_GPL(devm_pwm_put);
> +
>  #ifdef CONFIG_DEBUG_FS
>  static void pwm_dbg_show(struct pwm_chip *chip, struct seq_file *s)
>  {
> diff --git a/include/linux/pwm.h b/include/linux/pwm.h
> index 21d076c..af9c39a 100644
> --- a/include/linux/pwm.h
> +++ b/include/linux/pwm.h
> @@ -123,7 +123,10 @@ struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip,
>  					 const char *label);
>  
>  struct pwm_device *pwm_get(struct device *dev, const char *consumer);
> +struct pwm_device *devm_pwm_get(struct device *dev, const char *consumer);
> +
>  void pwm_put(struct pwm_device *pwm);
> +void devm_pwm_put(struct device *dev, struct pwm_device *pwm);

Can the managed variants be grouped together, please?

Looks good otherwise. Thanks for taking care of it.

Thierry

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