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Commit ad824783 authored by Alexandre Courbot's avatar Alexandre Courbot Committed by Linus Walleij
Browse files

gpio: better lookup method for platform GPIOs 



Change the format of the platform GPIO lookup tables to make them less
confusing and improve lookup efficiency.

The previous format was a single linked-list that required to compare
the device name and function ID of every single GPIO defined for each
lookup. Switch that to a list of per-device tables, so that the lookup
can be done in two steps, omitting the GPIOs that are not relevant for a
particular device.

The matching rules are now defined as follows:
- The device name must match *exactly*, and can be NULL for GPIOs not
  assigned to a particular device,
- If the function ID in the lookup table is NULL, the con_id argument of
  gpiod_get() will not be used for lookup. However, if it is defined, it
  must match exactly.
- The index must always match.

Signed-off-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
Acked-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent bdc54ef4

Documentation/gpio/board.txt

+17 −11
Original line number Diff line number Diff line
@@ -72,10 +72,11 @@ where 


  - chip_label is the label of the gpiod_chip instance providing the GPIO

  - chip_hwnum is the hardware number of the GPIO within the chip

  - dev_id is the identifier of the device that will make use of this GPIO. If

	NULL, the GPIO will be available to all devices.

  - dev_id is the identifier of the device that will make use of this GPIO. It

	can be NULL, in which case it will be matched for calls to gpiod_get()

	with a NULL device.

  - con_id is the name of the GPIO function from the device point of view. It

	can be NULL.

	can be NULL, in which case it will match any function.

  - idx is the index of the GPIO within the function.

  - flags is defined to specify the following properties:

	* GPIOF_ACTIVE_LOW	- to configure the GPIO as active-low
@@ -86,18 +87,23 @@ In the future, these flags might be extended to support more properties. 


Note that GPIO_LOOKUP() is just a shortcut to GPIO_LOOKUP_IDX() where idx = 0.



A lookup table can then be defined as follows:



	struct gpiod_lookup gpios_table[] = {

	GPIO_LOOKUP_IDX("gpio.0", 15, "foo.0", "led", 0, GPIO_ACTIVE_HIGH),

	GPIO_LOOKUP_IDX("gpio.0", 16, "foo.0", "led", 1, GPIO_ACTIVE_HIGH),

	GPIO_LOOKUP_IDX("gpio.0", 17, "foo.0", "led", 2, GPIO_ACTIVE_HIGH),

	GPIO_LOOKUP("gpio.0", 1, "foo.0", "power", GPIO_ACTIVE_LOW),

A lookup table can then be defined as follows, with an empty entry defining its

end:



struct gpiod_lookup_table gpios_table = {

	.dev_id = "foo.0",

	.table = {

		GPIO_LOOKUP_IDX("gpio.0", 15, "led", 0, GPIO_ACTIVE_HIGH),

		GPIO_LOOKUP_IDX("gpio.0", 16, "led", 1, GPIO_ACTIVE_HIGH),

		GPIO_LOOKUP_IDX("gpio.0", 17, "led", 2, GPIO_ACTIVE_HIGH),

		GPIO_LOOKUP("gpio.0", 1, "power", GPIO_ACTIVE_LOW),

		{ },

	},

};



And the table can be added by the board code as follows:



	gpiod_add_table(gpios_table, ARRAY_SIZE(gpios_table));

	gpiod_add_lookup_table(&gpios_table);



The driver controlling "foo.0" will then be able to obtain its GPIOs as follows:

drivers/gpio/gpiolib.c

+58 −50
Original line number Diff line number Diff line
@@ -2260,18 +2260,14 @@ void gpiod_set_value_cansleep(struct gpio_desc *desc, int value) 
EXPORT_SYMBOL_GPL(gpiod_set_value_cansleep);



/**

 * gpiod_add_table() - register GPIO device consumers

 * @table: array of consumers to register

 * @num: number of consumers in table

 * gpiod_add_lookup_table() - register GPIO device consumers

 * @table: table of consumers to register

 */

void gpiod_add_table(struct gpiod_lookup *table, size_t size)

void gpiod_add_lookup_table(struct gpiod_lookup_table *table)

{

	mutex_lock(&gpio_lookup_lock);



	while (size--) {

	list_add_tail(&table->list, &gpio_lookup_list);

		table++;

	}



	mutex_unlock(&gpio_lookup_lock);

}
@@ -2327,39 +2323,59 @@ static struct gpio_desc *acpi_find_gpio(struct device *dev, const char *con_id, 
	return desc;

}



static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,

				    unsigned int idx,

				    enum gpio_lookup_flags *flags)

static struct gpiod_lookup_table *gpiod_find_lookup_table(struct device *dev)

{

	const char *dev_id = dev ? dev_name(dev) : NULL;

	struct gpio_desc *desc = ERR_PTR(-ENODEV);

	unsigned int match, best = 0;

	struct gpiod_lookup *p;

	struct gpiod_lookup_table *table;



	mutex_lock(&gpio_lookup_lock);



	list_for_each_entry(p, &gpio_lookup_list, list) {

		match = 0;



		if (p->dev_id) {

			if (!dev_id || strcmp(p->dev_id, dev_id))

				continue;

	list_for_each_entry(table, &gpio_lookup_list, list) {

		if (table->dev_id && dev_id) {

			/*

			 * Valid strings on both ends, must be identical to have

			 * a match

			 */

			if (!strcmp(table->dev_id, dev_id))

				goto found;

		} else {

			/*

			 * One of the pointers is NULL, so both must be to have

			 * a match

			 */

			if (dev_id == table->dev_id)

				goto found;

		}

	}

	table = NULL;



			match += 2;

found:

	mutex_unlock(&gpio_lookup_lock);

	return table;

}



		if (p->con_id) {

			if (!con_id || strcmp(p->con_id, con_id))

				continue;

static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,

				    unsigned int idx,

				    enum gpio_lookup_flags *flags)

{

	struct gpio_desc *desc = ERR_PTR(-ENODEV);

	struct gpiod_lookup_table *table;

	struct gpiod_lookup *p;



			match += 1;

		}

	table = gpiod_find_lookup_table(dev);

	if (!table)

		return desc;



	for (p = &table->table[0]; p->chip_label; p++) {

		struct gpio_chip *chip;



		/* idx must always match exactly */

		if (p->idx != idx)

			continue;



		if (match > best) {

			struct gpio_chip *chip;

		/* If the lookup entry has a con_id, require exact match */

		if (p->con_id && (!con_id || strcmp(p->con_id, con_id)))

			continue;



		chip = find_chip_by_name(p->chip_label);
@@ -2375,24 +2391,16 @@ static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id, 
			continue;

		}



			desc = gpio_to_desc(chip->base + p->chip_hwnum);

		desc = gpiochip_offset_to_desc(chip, p->chip_hwnum);

		*flags = p->flags;



			if (match != 3)

				best = match;

			else

				break;

	}

	}



	mutex_unlock(&gpio_lookup_lock);



	return desc;

}



/**

 * gpio_get - obtain a GPIO for a given GPIO function

 * @dev:	GPIO consumer

 * @dev:	GPIO consumer, can be NULL for system-global GPIOs

 * @con_id:	function within the GPIO consumer

 *

 * Return the GPIO descriptor corresponding to the function con_id of device

include/linux/gpio/driver.h

+10 −11
Original line number Diff line number Diff line
@@ -141,7 +141,6 @@ enum gpio_lookup_flags { 
 * platform data.

 */

struct gpiod_lookup {

	struct list_head list;

	/*

	 * name of the chip the GPIO belongs to

	 */
@@ -150,10 +149,6 @@ struct gpiod_lookup { 
	 * hardware number (i.e. relative to the chip) of the GPIO

	 */

	u16 chip_hwnum;

	/*

	 * name of device that can claim this GPIO

	 */

	const char *dev_id;

	/*

	 * name of the GPIO from the device's point of view

	 */
@@ -168,28 +163,32 @@ struct gpiod_lookup { 
	enum gpio_lookup_flags flags;

};



struct gpiod_lookup_table {

	struct list_head list;

	const char *dev_id;

	struct gpiod_lookup table[];

};



/*

 * Simple definition of a single GPIO under a con_id

 */

#define GPIO_LOOKUP(_chip_label, _chip_hwnum, _dev_id, _con_id, _flags) \

	GPIO_LOOKUP_IDX(_chip_label, _chip_hwnum, _dev_id, _con_id, 0, _flags)

#define GPIO_LOOKUP(_chip_label, _chip_hwnum, _con_id, _flags) \

	GPIO_LOOKUP_IDX(_chip_label, _chip_hwnum, _con_id, 0, _flags)



/*

 * Use this macro if you need to have several GPIOs under the same con_id.

 * Each GPIO needs to use a different index and can be accessed using

 * gpiod_get_index()

 */

#define GPIO_LOOKUP_IDX(_chip_label, _chip_hwnum, _dev_id, _con_id, _idx, \

			_flags)                                           \

#define GPIO_LOOKUP_IDX(_chip_label, _chip_hwnum, _con_id, _idx, _flags)  \

{                                                                         \

	.chip_label = _chip_label,                                        \

	.chip_hwnum = _chip_hwnum,                                        \

	.dev_id = _dev_id,                                                \

	.con_id = _con_id,                                                \

	.idx = _idx,                                                      \

	.flags = _flags,                                                  \

}



void gpiod_add_table(struct gpiod_lookup *table, size_t size);

void gpiod_add_lookup_table(struct gpiod_lookup_table *table);



#endif