Re: [PATCH v3 2/4] gpiolib: add gpiod_get_array and gpiod_put_array functions

[Rojhalat Ibrahim <imr@xxxxxxxxxxx>]

On Tuesday 10 February 2015 12:40:34 Mika Westerberg wrote:
> [+Rafael]
> 
> On Mon, Feb 09, 2015 at 06:07:10PM +0100, Rojhalat Ibrahim wrote:
> > Introduce new functions for conveniently obtaining and disposing of an entire
> > array of GPIOs with one function call.
> > 
> > Suggested-by: Alexandre Courbot <acourbot@xxxxxxxxxx>
> > Signed-off-by: Rojhalat Ibrahim <imr@xxxxxxxxxxx>
> 
> Can you please next time CC me the whole series? Now it fails with:
> 

Sure. Sorry about that.

> drivers/gpio/gpiolib.c: In function ‘dt_gpio_count’:
> drivers/gpio/gpiolib.c:1812:29: error: ‘gpio_suffixes’ undeclared (first
> use in this function)
>   for (i = 0; i < ARRAY_SIZE(gpio_suffixes); i++) {
>                              ^
> include/linux/kernel.h:54:33: note: in definition of macro ‘ARRAY_SIZE’
>  #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) +
> __must_be_array(arr))
> 
> and so on.
> 
> > ---
> > Change log:
> >   v3: - rebase on current linux-gpio devel branch
> >       - fix ACPI GPIO counting
> >       - allow for zero-sized arrays
> >       - make the flags argument mandatory for the new functions
> >       - clarify documentation
> >   v2: change interface
> > 
> >  Documentation/gpio/consumer.txt |  33 +++++-
> >  drivers/gpio/gpiolib.c          | 231 ++++++++++++++++++++++++++++++++++++++++
> >  include/linux/gpio/consumer.h   |  46 ++++++++
> >  3 files changed, 307 insertions(+), 3 deletions(-)
> > 
> > diff --git a/Documentation/gpio/consumer.txt b/Documentation/gpio/consumer.txt
> > index d85fbae..85a7e30 100644
> > --- a/Documentation/gpio/consumer.txt
> > +++ b/Documentation/gpio/consumer.txt
> > @@ -58,7 +58,6 @@ pattern where a GPIO is optional, the gpiod_get_optional() and
> >  gpiod_get_index_optional() functions can be used. These functions return NULL
> >  instead of -ENOENT if no GPIO has been assigned to the requested function:
> >  
> > -
> >  	struct gpio_desc *gpiod_get_optional(struct device *dev,
> >  					     const char *con_id,
> >  					     enum gpiod_flags flags)
> > @@ -68,6 +67,27 @@ instead of -ENOENT if no GPIO has been assigned to the requested function:
> >  						   unsigned int index,
> >  						   enum gpiod_flags flags)
> >  
> > +For a function using multiple GPIOs all of those can be obtained with one call:
> > +
> > +	struct gpio_descs *gpiod_get_array(struct device *dev,
> > +					   const char *con_id,
> > +					   enum gpiod_flags flags)
> > +
> > +This function returns a struct gpio_descs which contains an array of
> > +descriptors:
> > +
> > +	struct gpio_descs {
> > +		unsigned int array_size;
> > +		struct gpio_desc *desc_array[];
> > +	}
> > +
> > +The following function returns NULL instead of -ENOENT if no GPIOs have been
> > +assigned to the requested function:
> > +
> > +	struct gpio_descs *gpiod_get_array_optional(struct device *dev,
> > +						    const char *con_id,
> > +						    enum gpiod_flags flags)
> > +
> >  Device-managed variants of these functions are also defined:
> >  
> >  	struct gpio_desc *devm_gpiod_get(struct device *dev, const char *con_id,
> > @@ -91,8 +111,15 @@ A GPIO descriptor can be disposed of using the gpiod_put() function:
> >  
> >  	void gpiod_put(struct gpio_desc *desc)
> >  
> > -It is strictly forbidden to use a descriptor after calling this function. The
> > -device-managed variant is, unsurprisingly:
> > +For an array of GPIOs this function can be used:
> > +
> > +	void gpiod_put_array(struct gpio_descs *descs)
> > +
> > +It is strictly forbidden to use a descriptor after calling these functions.
> > +It is also not allowed to individually release descriptors (using gpiod_put())
> > +from an array acquired with gpiod_get_array().
> > +
> > +The device-managed variant is, unsurprisingly:
> >  
> >  	void devm_gpiod_put(struct device *dev, struct gpio_desc *desc)
> >  
> > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > index ff2b80d..d4153e0 100644
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -1804,6 +1804,158 @@ static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
> >  	return desc;
> >  }
> >  
> > +static int dt_gpio_count(struct device *dev, const char *con_id)
> > +{
> > +	int ret;
> > +	char propname[32];
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(gpio_suffixes); i++) {
> > +		if (con_id)
> > +			snprintf(propname, sizeof(propname), "%s-%s",
> > +				 con_id, gpio_suffixes[i]);
> > +		else
> > +			snprintf(propname, sizeof(propname), "%s",
> > +				 gpio_suffixes[i]);
> > +
> > +		ret = of_gpio_named_count(dev->of_node, propname);
> > +		if (ret >= 0)
> > +			break;
> > +	}
> > +	return ret;
> > +}
> > +
> > +#ifdef CONFIG_ACPI
> > +
> > +static unsigned int acpi_gpio_package_count(const union acpi_object *obj)
> > +{
> > +	const union acpi_object *element = obj->package.elements;
> > +	const union acpi_object *end = element + obj->package.count;
> > +	unsigned int count = 0;
> > +
> > +	while (element < end) {
> > +		if (element->type == ACPI_TYPE_LOCAL_REFERENCE)
> > +			count++;
> > +
> > +		element++;
> > +	}
> > +	return count;
> > +}
> > +
> > +static int acpi_find_gpio_count(struct acpi_resource *ares, void *data)
> > +{
> > +	unsigned int *count = data;
> > +
> > +	if (ares->type == ACPI_RESOURCE_TYPE_GPIO)
> > +		*count += ares->data.gpio.pin_table_length;
> > +
> > +	return 1;
> > +}
> > +
> > +static int acpi_gpio_count(struct device *dev, const char *con_id)
> > +{
> > +	struct acpi_device *adev = ACPI_COMPANION(dev);
> 
> Should you check that the ACPI companion device actually exists here or
> is it checked somewhere before already?
> 
> > +	const union acpi_object *obj;
> > +	const struct acpi_gpio_mapping *gm;
> > +	int count = -ENOENT;
> > +	int ret;
> > +	char propname[32];
> > +	unsigned int i;
> > +
> > +	/* Try first from _DSD */
> > +	for (i = 0; i < ARRAY_SIZE(gpio_suffixes); i++) {
> > +		if (con_id && strcmp(con_id, "gpios"))
> > +			snprintf(propname, sizeof(propname), "%s-%s",
> > +				 con_id, gpio_suffixes[i]);
> 
> I'm assuming some previous patch added gpio_suffixes[].
> 
> > +		else
> > +			snprintf(propname, sizeof(propname), "%s",
> > +				 gpio_suffixes[i]);
> > +
> > +		ret = acpi_dev_get_property(adev, propname, ACPI_TYPE_ANY,
> > +					    &obj);
> > +		if (ret == 0) {
> > +			if (obj->type == ACPI_TYPE_LOCAL_REFERENCE)
> > +				count = 1;
> > +			else if (obj->type == ACPI_TYPE_PACKAGE)
> > +				count = acpi_gpio_package_count(obj);
> > +		} else if (adev->driver_gpios) {
> > +			for (gm = adev->driver_gpios; gm->name; gm++)
> > +				if (strcmp(propname, gm->name) == 0) {
> > +					count = gm->size;
> > +					break;
> > +				}
> > +		}
> > +		if (count >= 0)
> > +			break;
> > +	}
> > +
> > +	/* Then from plain _CRS GPIOs */
> > +	if (count < 0) {
> > +		struct list_head resource_list;
> > +		unsigned int crs_count = 0;
> > +
> > +		INIT_LIST_HEAD(&resource_list);
> > +		acpi_dev_get_resources(adev, &resource_list,
> > +				       acpi_find_gpio_count, &crs_count);
> > +		acpi_dev_free_resource_list(&resource_list);
> > +		if (crs_count > 0)
> > +			count = crs_count;
> > +	}
> > +	return count;
> > +}
> 
> Otherwise the ACPI parts look good to me. I still want to test this,
> though.
> 

Great.

> > +
> > +#else
> > +
> > +static int acpi_gpio_count(struct device *dev, const char *con_id)
> > +{
> > +	return -ENODEV;
> > +}
> > +
> > +#endif
> > +
> > +static int lut_gpio_count(struct device *dev, const char *con_id)
> > +{
> > +	struct gpiod_lookup_table *table;
> > +	struct gpiod_lookup *p;
> > +	unsigned int count = 0;
> > +
> > +	table = gpiod_find_lookup_table(dev);
> > +	if (!table)
> > +		return -ENOENT;
> > +
> > +	for (p = &table->table[0]; p->chip_label; p++) {
> > +		if ((con_id && p->con_id && !strcmp(con_id, p->con_id)) ||
> > +		    (!con_id && !p->con_id))
> > +			count++;
> > +	}
> > +	if (!count)
> > +		return -ENOENT;
> > +
> > +	return count;
> > +}
> > +
> > +/**
> > + * gpiod_count - return the number of GPIOs associated with a device / function
> > + *		or -ENOENT if no GPIO has been assigned to the requested function
> > + * @dev:	GPIO consumer, can be NULL for system-global GPIOs
> > + * @con_id:	function within the GPIO consumer
> > + */
> > +int gpiod_count(struct device *dev, const char *con_id)
> > +{
> > +	int count = -ENOENT;
> > +
> > +	if (IS_ENABLED(CONFIG_OF) && dev && dev->of_node)
> > +		count = dt_gpio_count(dev, con_id);
> > +	else if (IS_ENABLED(CONFIG_ACPI) && dev && ACPI_HANDLE(dev))
> > +		count = acpi_gpio_count(dev, con_id);
> 
> Aha, so you here you checked for the ACPI compation, all right then.
> 
> > +
> > +	if (count < 0)
> > +		count = lut_gpio_count(dev, con_id);
> > +
> > +	return count;
> > +}
> > +EXPORT_SYMBOL_GPL(gpiod_count);
> > +
> >  /**
> >   * gpiod_get - obtain a GPIO for a given GPIO function
> >   * @dev:	GPIO consumer, can be NULL for system-global GPIOs
> > @@ -2005,6 +2157,70 @@ struct gpio_desc *__must_check __gpiod_get_index_optional(struct device *dev,
> >  EXPORT_SYMBOL_GPL(__gpiod_get_index_optional);
> >  
> >  /**
> > + * gpiod_get_array - obtain multiple GPIOs from a multi-index GPIO function
> > + * @dev:	GPIO consumer, can be NULL for system-global GPIOs
> > + * @con_id:	function within the GPIO consumer
> > + * @flags:	optional GPIO initialization flags
> > + *
> > + * This function acquires all the GPIOs defined under a given function.
> > + *
> > + * Return a struct gpio_descs containing an array of descriptors, -ENOENT if
> > + * no GPIO has been assigned to the requested function, or another IS_ERR()
> > + * code if an error occurred while trying to acquire the GPIOs.
> > + */
> > +struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
> > +						const char *con_id,
> > +						enum gpiod_flags flags)
> > +{
> > +	struct gpio_desc *desc;
> > +	struct gpio_descs *descs;
> > +	int count;
> > +
> > +	count = gpiod_count(dev, con_id);
> > +	if (count < 0)
> > +		return ERR_PTR(count);
> > +
> > +	descs = kzalloc(sizeof(*descs) + sizeof(descs->desc_array[0]) * count,
> > +			GFP_KERNEL);
> 
> Should you return ERR_PTR(-ENOMEM) here if the allocation fails?
> 

Of course. I'll put it in the next revision.

> > +
> > +	for (descs->array_size = 0; descs->array_size < count; ) {
>                                                               ^
>                                                               |
>                                                               +-- extra whitespace
> 
> > +		desc = gpiod_get_index(dev, con_id, descs->array_size, flags);
> > +		if (IS_ERR(desc)) {
> > +			gpiod_put_array(descs);
> > +			return ERR_PTR(PTR_ERR(desc));
> 
> Uh, why not
> 
> 	return desc
> 
> ?

Because of the different pointer type. desc is a pointer to a GPIO descriptor
whereas the return type of the function is a pointer to struct gpio_descs.

> 
> > +		}
> > +		descs->desc_array[descs->array_size] = desc;
> > +		descs->array_size++;
> > +	}
> > +	return descs;
> > +}
> > +EXPORT_SYMBOL_GPL(gpiod_get_array);
> > +
> > +/**
> > + * gpiod_get_array_optional - obtain multiple GPIOs from a multi-index GPIO
> > + *                            function
> > + * @dev:	GPIO consumer, can be NULL for system-global GPIOs
> > + * @con_id:	function within the GPIO consumer
> > + * @flags:	optional GPIO initialization flags
> > + *
> > + * This is equivalent to gpiod_get_array(), except that when no GPIO was
> > + * assigned to the requested function it will return NULL.
> > + */
> > +struct gpio_descs *__must_check gpiod_get_array_optional(struct device *dev,
> > +							const char *con_id,
> > +							enum gpiod_flags flags)
> > +{
> > +	struct gpio_descs *descs;
> > +
> > +	descs = gpiod_get_array(dev, con_id, flags);
> > +	if (IS_ERR(descs) && (PTR_ERR(descs) == -ENOENT))
> > +		return NULL;
> 
> The caller still needs to handle other error codes (than -ENOENT), so
> would it be better to just have only gpiod_get_array()?
> 

This follows the same pattern as gpiod_get_optional() and
gpiod_get_index_optional()

>From Documentation/gpio/consumer.txt:

This is useful to discriminate between mere
errors and an absence of GPIO for optional GPIO parameters. For the common
pattern where a GPIO is optional, the gpiod_get_optional() and
gpiod_get_index_optional() functions can be used. These functions return NULL
instead of -ENOENT if no GPIO has been assigned to the requested function

> > +
> > +	return descs;
> > +}
> > +EXPORT_SYMBOL_GPL(gpiod_get_array_optional);
> > +
> > +/**
> >   * gpiod_put - dispose of a GPIO descriptor
> >   * @desc:	GPIO descriptor to dispose of
> >   *
> > @@ -2016,6 +2232,21 @@ void gpiod_put(struct gpio_desc *desc)
> >  }
> >  EXPORT_SYMBOL_GPL(gpiod_put);
> >  
> > +/**
> > + * gpiod_put_array - dispose of multiple GPIO descriptors
> > + * @descs:	struct gpio_descs containing an array of descriptors
> > + */
> > +void gpiod_put_array(struct gpio_descs *descs)
> > +{
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < descs->array_size; i++)
> > +		gpiod_put(descs->desc_array[i]);
> > +
> > +	kfree(descs);
> > +}
> > +EXPORT_SYMBOL_GPL(gpiod_put_array);
> > +
> >  #ifdef CONFIG_DEBUG_FS
> >  
> >  static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
> > diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
> > index 45afc2d..6b1c389 100644
> > --- a/include/linux/gpio/consumer.h
> > +++ b/include/linux/gpio/consumer.h
> > @@ -16,6 +16,15 @@ struct device;
> >   */
> >  struct gpio_desc;
> >  
> > +/**
> > + * Struct containing an array of descriptors that can be obtained using
> > + * gpiod_get_array().
> > + */
> > +struct gpio_descs {
> > +	unsigned int array_size;
> > +	struct gpio_desc *desc_array[];
> > +};
> > +
> >  #define GPIOD_FLAGS_BIT_DIR_SET		BIT(0)
> >  #define GPIOD_FLAGS_BIT_DIR_OUT		BIT(1)
> >  #define GPIOD_FLAGS_BIT_DIR_VAL		BIT(2)
> > @@ -34,6 +43,9 @@ enum gpiod_flags {
> >  
> >  #ifdef CONFIG_GPIOLIB
> >  
> > +/* Return the number of GPIOs associated with a device / function */
> > +int gpiod_count(struct device *dev, const char *con_id);
> > +
> >  /* Acquire and dispose GPIOs */
> >  struct gpio_desc *__must_check __gpiod_get(struct device *dev,
> >  					 const char *con_id,
> > @@ -49,7 +61,14 @@ struct gpio_desc *__must_check __gpiod_get_index_optional(struct device *dev,
> >  							const char *con_id,
> >  							unsigned int index,
> >  							enum gpiod_flags flags);
> > +struct gpio_descs *__must_check gpiod_get_array(struct device *dev,
> > +						const char *con_id,
> > +						enum gpiod_flags flags);
> > +struct gpio_descs *__must_check gpiod_get_array_optional(struct device *dev,
> > +							const char *con_id,
> > +							enum gpiod_flags flags);
> >  void gpiod_put(struct gpio_desc *desc);
> > +void gpiod_put_array(struct gpio_descs *descs);
> >  
> >  struct gpio_desc *__must_check __devm_gpiod_get(struct device *dev,
> >  					      const char *con_id,
> > @@ -113,6 +132,11 @@ struct gpio_desc *devm_get_gpiod_from_child(struct device *dev,
> >  					    struct fwnode_handle *child);
> >  #else /* CONFIG_GPIOLIB */
> >  
> > +static inline int gpiod_count(struct device *dev, const char *con_id)
> > +{
> > +	return 0;
> > +}
> > +
> >  static inline struct gpio_desc *__must_check __gpiod_get(struct device *dev,
> >  						const char *con_id,
> >  						enum gpiod_flags flags)
> > @@ -142,6 +166,20 @@ __gpiod_get_index_optional(struct device *dev, const char *con_id,
> >  	return ERR_PTR(-ENOSYS);
> >  }
> >  
> > +static inline struct gpio_descs *__must_check
> > +gpiod_get_array(struct device *dev, const char *con_id,
> > +		enum gpiod_flags flags)
> > +{
> > +	return ERR_PTR(-ENOSYS);
> 
> That should be -ENXIO.
> 

Why? All the other functions in this section return -ENOSYS.

According to include/uapi/asm-generic/errno.h
ENOSYS means "Function not implemented"
and in include/uapi/asm-generic/errno-base.h it says
ENXIO stands for "No such device or address".

If ENXIO is more correct here (and I don't see why),
then it should at least be consistent for all functions, right?

> > +}
> > +
> > +static inline struct gpio_descs *__must_check
> > +gpiod_get_array_optional(struct device *dev, const char *con_id,
> > +			 enum gpiod_flags flags)
> > +{
> > +	return ERR_PTR(-ENOSYS);
> 
> Ditto.
> 
> > +}
> > +
> >  static inline void gpiod_put(struct gpio_desc *desc)
> >  {
> >  	might_sleep();
> > @@ -150,6 +188,14 @@ static inline void gpiod_put(struct gpio_desc *desc)
> >  	WARN_ON(1);
> >  }
> >  
> > +static inline void gpiod_put_array(struct gpio_descs *descs)
> > +{
> > +	might_sleep();
> > +
> > +	/* GPIO can never have been requested */
> > +	WARN_ON(1);
> > +}
> > +
> >  static inline struct gpio_desc *__must_check
> >  __devm_gpiod_get(struct device *dev,
> >  		 const char *con_id,
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