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gpio: better lookup method for platform GPIOs

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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: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Alexandre Courbot 2013-12-03 12:20:11 +09:00 committed by Linus Walleij
parent bdc54ef45d
commit ad824783fb
3 changed files with 87 additions and 74 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
Documentation/gpio/board.txt
View File

@ -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:
A lookup table can then be defined as follows, with an empty entry defining its
end:
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),
};
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:

112
drivers/gpio/gpiolib.c
View File

@ -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++;
}
list_add_tail(&table->list, &gpio_lookup_list);
mutex_unlock(&gpio_lookup_lock);
}
@ -2327,72 +2323,84 @@ static struct gpio_desc *acpi_find_gpio(struct device *dev, const char *con_id,
return desc;
}
static struct gpiod_lookup_table *gpiod_find_lookup_table(struct device *dev)
{
const char *dev_id = dev ? dev_name(dev) : NULL;
struct gpiod_lookup_table *table;
mutex_lock(&gpio_lookup_lock);
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;
found:
mutex_unlock(&gpio_lookup_lock);
return table;
}
static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
unsigned int idx,
enum gpio_lookup_flags *flags)
{
const char *dev_id = dev ? dev_name(dev) : NULL;
struct gpio_desc *desc = ERR_PTR(-ENODEV);
unsigned int match, best = 0;
struct gpiod_lookup_table *table;
struct gpiod_lookup *p;
mutex_lock(&gpio_lookup_lock);
table = gpiod_find_lookup_table(dev);
if (!table)
return desc;
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;
match += 2;
}
if (p->con_id) {
if (!con_id || strcmp(p->con_id, con_id))
continue;
match += 1;
}
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);
chip = find_chip_by_name(p->chip_label);
if (!chip) {
dev_warn(dev, "cannot find GPIO chip %s\n",
p->chip_label);
continue;
}
if (chip->ngpio <= p->chip_hwnum) {
dev_warn(dev, "GPIO chip %s has %d GPIOs\n",
chip->label, chip->ngpio);
continue;
}
desc = gpio_to_desc(chip->base + p->chip_hwnum);
*flags = p->flags;
if (match != 3)
best = match;
else
break;
if (!chip) {
dev_warn(dev, "cannot find GPIO chip %s\n",
p->chip_label);
continue;
}
}
mutex_unlock(&gpio_lookup_lock);
if (chip->ngpio <= p->chip_hwnum) {
dev_warn(dev, "GPIO chip %s has %d GPIOs\n",
chip->label, chip->ngpio);
continue;
}
desc = gpiochip_offset_to_desc(chip, p->chip_hwnum);
*flags = p->flags;
}
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

21
include/linux/gpio/driver.h
View File

@ -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