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Date:   Sun, 15 Sep 2019 14:47:00 +0100
From:   Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
To:     William Breathitt Gray <vilhelm.gray@gmail.com>
Cc:     linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org
Subject: Re: [RFC 1/4] counter: Simplify the count_read and count_write
 callbacks
Message-ID: <20190915144700.0f7a361d@archlinux>
In-Reply-To: <20190915143917.61385369@archlinux>
References: <20190915055759.408690-1-vilhelm.gray@gmail.com>
        <20190915055759.408690-2-vilhelm.gray@gmail.com>
        <20190915143917.61385369@archlinux>
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On Sun, 15 Sep 2019 14:39:17 +0100
Jonathan Cameron <jic23@jic23.retrosnub.co.uk> wrote:

> On Sun, 15 Sep 2019 14:57:56 +0900
> William Breathitt Gray <vilhelm.gray@gmail.com> wrote:
> 
> > The count_read and count_write callbacks are simplified to pass val as
> > unsigned long rather than as an opaque data structure. The opaque
> > counter_count_read_value and counter_count_write_value structures,
> > counter_count_value_type enum, and relevant counter_count_read_value_set
> > and counter_count_write_value_get functions, are removed as they are no
> > longer used.
> > 
> > Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>  
> 
> Seems like a sensible bit of excessive abstraction removal to me.  I'm not
> totally sure why these got so complex in the first place though.
Ah. I should have read the cover letter rather than just diving in the code :)
All explained there I see.

> 
> Can you recall the reason as it might help to judge why we no longer
> think the same?
> 
> Thanks,
> 
> Jonathan
> > ---
> >  drivers/counter/counter.c | 66 +++++----------------------------------
> >  include/linux/counter.h   | 43 +++----------------------
> >  2 files changed, 12 insertions(+), 97 deletions(-)
> > 
> > diff --git a/drivers/counter/counter.c b/drivers/counter/counter.c
> > index 106bc7180cd8..1d08f1437b1b 100644
> > --- a/drivers/counter/counter.c
> > +++ b/drivers/counter/counter.c
> > @@ -246,60 +246,6 @@ void counter_signal_read_value_set(struct counter_signal_read_value *const val,
> >  }
> >  EXPORT_SYMBOL_GPL(counter_signal_read_value_set);
> >  
> > -/**
> > - * counter_count_read_value_set - set counter_count_read_value data
> > - * @val:	counter_count_read_value structure to set
> > - * @type:	property Count data represents
> > - * @data:	Count data
> > - *
> > - * This function sets an opaque counter_count_read_value structure with the
> > - * provided Count data.
> > - */
> > -void counter_count_read_value_set(struct counter_count_read_value *const val,
> > -				  const enum counter_count_value_type type,
> > -				  void *const data)
> > -{
> > -	switch (type) {
> > -	case COUNTER_COUNT_POSITION:
> > -		val->len = sprintf(val->buf, "%lu\n", *(unsigned long *)data);
> > -		break;
> > -	default:
> > -		val->len = 0;
> > -	}
> > -}
> > -EXPORT_SYMBOL_GPL(counter_count_read_value_set);
> > -
> > -/**
> > - * counter_count_write_value_get - get counter_count_write_value data
> > - * @data:	Count data
> > - * @type:	property Count data represents
> > - * @val:	counter_count_write_value structure containing data
> > - *
> > - * This function extracts Count data from the provided opaque
> > - * counter_count_write_value structure and stores it at the address provided by
> > - * @data.
> > - *
> > - * RETURNS:
> > - * 0 on success, negative error number on failure.
> > - */
> > -int counter_count_write_value_get(void *const data,
> > -				  const enum counter_count_value_type type,
> > -				  const struct counter_count_write_value *const val)
> > -{
> > -	int err;
> > -
> > -	switch (type) {
> > -	case COUNTER_COUNT_POSITION:
> > -		err = kstrtoul(val->buf, 0, data);
> > -		if (err)
> > -			return err;
> > -		break;
> > -	}
> > -
> > -	return 0;
> > -}
> > -EXPORT_SYMBOL_GPL(counter_count_write_value_get);
> > -
> >  struct counter_attr_parm {
> >  	struct counter_device_attr_group *group;
> >  	const char *prefix;
> > @@ -788,13 +734,13 @@ static ssize_t counter_count_show(struct device *dev,
> >  	const struct counter_count_unit *const component = devattr->component;
> >  	struct counter_count *const count = component->count;
> >  	int err;
> > -	struct counter_count_read_value val = { .buf = buf };
> > +	unsigned long val;
> >  
> >  	err = counter->ops->count_read(counter, count, &val);
> >  	if (err)
> >  		return err;
> >  
> > -	return val.len;
> > +	return sprintf(buf, "%lu\n", val);
> >  }
> >  
> >  static ssize_t counter_count_store(struct device *dev,
> > @@ -806,9 +752,13 @@ static ssize_t counter_count_store(struct device *dev,
> >  	const struct counter_count_unit *const component = devattr->component;
> >  	struct counter_count *const count = component->count;
> >  	int err;
> > -	struct counter_count_write_value val = { .buf = buf };
> > +	unsigned long val;
> > +
> > +	err = kstrtoul(buf, 0, &val);
> > +	if (err)
> > +		return err;
> >  
> > -	err = counter->ops->count_write(counter, count, &val);
> > +	err = counter->ops->count_write(counter, count, val);
> >  	if (err)
> >  		return err;
> >  
> > diff --git a/include/linux/counter.h b/include/linux/counter.h
> > index a061cdcdef7c..7e40796598a6 100644
> > --- a/include/linux/counter.h
> > +++ b/include/linux/counter.h
> > @@ -300,24 +300,6 @@ struct counter_signal_read_value {
> >  	size_t len;
> >  };
> >  
> > -/**
> > - * struct counter_count_read_value - Opaque Count read value
> > - * @buf:	string representation of Count read value
> > - * @len:	length of string in @buf
> > - */
> > -struct counter_count_read_value {
> > -	char *buf;
> > -	size_t len;
> > -};
> > -
> > -/**
> > - * struct counter_count_write_value - Opaque Count write value
> > - * @buf:	string representation of Count write value
> > - */
> > -struct counter_count_write_value {
> > -	const char *buf;
> > -};
> > -
> >  /**
> >   * struct counter_ops - Callbacks from driver
> >   * @signal_read:	optional read callback for Signal attribute. The read
> > @@ -328,15 +310,10 @@ struct counter_count_write_value {
> >   *			signal_read callback.
> >   * @count_read:		optional read callback for Count attribute. The read
> >   *			value of the respective Count should be passed back via
> > - *			the val parameter. val points to an opaque type which
> > - *			should be set only by calling the
> > - *			counter_count_read_value_set function from within the
> > - *			count_read callback.
> > + *			the val parameter.
> >   * @count_write:	optional write callback for Count attribute. The write
> >   *			value for the respective Count is passed in via the val
> > - *			parameter. val points to an opaque type which should be
> > - *			accessed only by calling the
> > - *			counter_count_write_value_get function.
> > + *			parameter.
> >   * @function_get:	function to get the current count function mode. Returns
> >   *			0 on success and negative error code on error. The index
> >   *			of the respective Count's returned function mode should
> > @@ -357,11 +334,9 @@ struct counter_ops {
> >  			   struct counter_signal *signal,
> >  			   struct counter_signal_read_value *val);
> >  	int (*count_read)(struct counter_device *counter,
> > -			  struct counter_count *count,
> > -			  struct counter_count_read_value *val);
> > +			  struct counter_count *count, unsigned long *val);
> >  	int (*count_write)(struct counter_device *counter,
> > -			   struct counter_count *count,
> > -			   struct counter_count_write_value *val);
> > +			   struct counter_count *count, unsigned long val);
> >  	int (*function_get)(struct counter_device *counter,
> >  			    struct counter_count *count, size_t *function);
> >  	int (*function_set)(struct counter_device *counter,
> > @@ -486,19 +461,9 @@ enum counter_signal_value_type {
> >  	COUNTER_SIGNAL_LEVEL = 0
> >  };
> >  
> > -enum counter_count_value_type {
> > -	COUNTER_COUNT_POSITION = 0,
> > -};
> > -
> >  void counter_signal_read_value_set(struct counter_signal_read_value *const val,
> >  				   const enum counter_signal_value_type type,
> >  				   void *const data);
> > -void counter_count_read_value_set(struct counter_count_read_value *const val,
> > -				  const enum counter_count_value_type type,
> > -				  void *const data);
> > -int counter_count_write_value_get(void *const data,
> > -				  const enum counter_count_value_type type,
> > -				  const struct counter_count_write_value *const val);
> >  
> >  int counter_register(struct counter_device *const counter);
> >  void counter_unregister(struct counter_device *const counter);  
>