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SubjectRe: [RFC 1/4] counter: Simplify the count_read and count_write callbacks
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);
>

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