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

[Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>]

[+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:

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.

> +
> +#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?

> +
> +	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

?

> +		}
> +		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()?

> +
> +	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.

> +}
> +
> +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,
> -- 
> 2.0.5
> 
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