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Message-ID: <1385982101-24706-1-git-send-email-acourbot@nvidia.com>
Date: Mon, 2 Dec 2013 20:01:41 +0900
From: Alexandre Courbot <acourbot@...dia.com>
To: Linus Walleij <linus.walleij@...aro.org>,
Mika Westerberg <mika.westerberg@...ux.intel.com>,
Andy Shevchenko <andy.shevchenko@...il.com>,
Rhyland Klein <rklein@...dia.com>,
Heikki Krogerus <heikki.krogerus@...ux.intel.com>
CC: <linux-gpio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
Alexandre Courbot <acourbot@...dia.com>
Subject: [PATCH v2] 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: Alexandre Courbot <acourbot@...dia.com>
Acked-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
---
Changes since v1:
- Applied most fixes suggested by Andy
- Hopefully safer and less confusing table lookup algorithm
- Added Mika's ack
Documentation/gpio/board.txt | 25 ++++++----
drivers/gpio/gpiolib.c | 109 +++++++++++++++++++++++--------------------
include/linux/gpio/driver.h | 22 ++++-----
3 files changed, 85 insertions(+), 71 deletions(-)
diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt
index 0d03506f2cc5..a4fdd96cef93 100644
--- a/Documentation/gpio/board.txt
+++ b/Documentation/gpio/board.txt
@@ -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
@@ -88,16 +89,20 @@ 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),
- };
+struct gpiod_lookup_table gpios_table = {
+ .dev_id = "foo.0",
+ .size = 4,
+ .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:
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f72618ba716a..d17d6eabed6a 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2259,18 +2259,14 @@ 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);
}
@@ -2326,72 +2322,85 @@ 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;
+ 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 end;
+ } else {
+ /*
+ * One of the pointers is NULL, so both must be to have
+ * a match
+ */
+ if (dev_id == table->dev_id)
+ goto end;
+ }
+ }
+ table = NULL;
- if (p->dev_id) {
- if (!dev_id || strcmp(p->dev_id, dev_id))
- continue;
+end:
+ mutex_unlock(&gpio_lookup_lock);
+ return table;
+}
- match += 2;
- }
+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;
+ int i;
- if (p->con_id) {
- if (!con_id || strcmp(p->con_id, con_id))
- continue;
+ table = gpiod_find_lookup_table(dev);
+ if (!table)
+ return desc;
- match += 1;
- }
+ for (i = 0; i < table->size; i++) {
+ struct gpio_chip *chip;
+ struct gpiod_lookup *p = &table->table[i];
+ /* idx must always match exactly */
if (p->idx != idx)
continue;
- if (match > best) {
- struct gpio_chip *chip;
-
- chip = find_chip_by_name(p->chip_label);
-
- if (!chip) {
- dev_warn(dev, "cannot find GPIO chip %s\n",
- p->chip_label);
- continue;
- }
+ /* If the lookup entry has a con_id, require exact match */
+ if (p->con_id && (!con_id || strcmp(p->con_id, con_id)))
+ continue;
- if (chip->ngpio <= p->chip_hwnum) {
- dev_warn(dev, "GPIO chip %s has %d GPIOs\n",
- chip->label, chip->ngpio);
- continue;
- }
+ chip = find_chip_by_name(p->chip_label);
- desc = gpio_to_desc(chip->base + p->chip_hwnum);
- *flags = p->flags;
+ if (!chip) {
+ dev_warn(dev, "cannot find GPIO chip %s\n",
+ p->chip_label);
+ continue;
+ }
- if (match != 3)
- best = match;
- else
- break;
+ if (chip->ngpio <= p->chip_hwnum) {
+ dev_warn(dev, "GPIO chip %s has %d GPIOs\n",
+ chip->label, chip->ngpio);
+ continue;
}
- }
- mutex_unlock(&gpio_lookup_lock);
+ 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
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 3ea2cf6b0e6c..44893ef40817 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -140,7 +140,6 @@ 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 {
*/
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
*/
const char *con_id;
@@ -167,28 +162,33 @@ struct gpiod_lookup {
enum gpio_lookup_flags flags;
};
+struct gpiod_lookup_table {
+ struct list_head list;
+ const char *dev_id;
+ unsigned int size;
+ 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
--
1.8.4.2
--
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