[PATCH v6 4/8] gpiolib: Add support for GPIO lookup by line name
From: Geert Uytterhoeven
Date: Tue Mar 24 2020 - 09:57:28 EST
Currently a GPIO lookup table can only refer to a specific GPIO by a
tuple, consisting of a GPIO controller label and a GPIO offset inside
the controller.
However, a GPIO may also carry a line name, defined by DT or ACPI.
If present, the line name is the most use-centric way to refer to a
GPIO. Hence add support for looking up GPIOs by line name.
Implement this by reusing the existing gpiod_lookup infrastructure.
Rename gpiod_lookup.chip_label to gpiod_lookup.key, to make it clear
that this field can have two meanings, and update the kerneldoc and
GPIO_LOOKUP*() macros.
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Reviewed-by: Ulrich Hecht <uli+renesas@xxxxxxxx>
Reviewed-by: Eugeniu Rosca <erosca@xxxxxxxxxxxxxx>
Tested-by: Eugeniu Rosca <erosca@xxxxxxxxxxxxxx>
---
v6:
- Update Documentation/driver-api/gpio/board.rst,
- Reword rationale,
v5:
- Add Reviewed-by, Tested-by,
v4:
- Add Reviewed-by,
- Rename gpiod_lookup.chip_label.
- Use U16_MAX instead of (u16)-1,
v3:
- New.
---
Documentation/driver-api/gpio/board.rst | 10 ++++++----
drivers/gpio/gpiolib.c | 22 +++++++++++++++++-----
include/linux/gpio/machine.h | 15 ++++++++-------
3 files changed, 31 insertions(+), 16 deletions(-)
diff --git a/Documentation/driver-api/gpio/board.rst b/Documentation/driver-api/gpio/board.rst
index ce91518bf9f48ded..0ad1f8cacf5e5d26 100644
--- a/Documentation/driver-api/gpio/board.rst
+++ b/Documentation/driver-api/gpio/board.rst
@@ -113,13 +113,15 @@ files that desire to do so need to include the following header::
GPIOs are mapped by the means of tables of lookups, containing instances of the
gpiod_lookup structure. Two macros are defined to help declaring such mappings::
- GPIO_LOOKUP(chip_label, chip_hwnum, con_id, flags)
- GPIO_LOOKUP_IDX(chip_label, chip_hwnum, con_id, idx, flags)
+ GPIO_LOOKUP(key, chip_hwnum, con_id, flags)
+ GPIO_LOOKUP_IDX(key, chip_hwnum, con_id, idx, flags)
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
+ - key is either the label of the gpiod_chip instance providing the GPIO, or
+ the GPIO line name
+ - chip_hwnum is the hardware number of the GPIO within the chip, or U16_MAX
+ to indicate that key is a GPIO line name
- con_id is the name of the GPIO function from the device point of view. It
can be NULL, in which case it will match any function.
- idx is the index of the GPIO within the function.
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 8d7366f4451fe695..c756602e249c052e 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -4643,7 +4643,7 @@ static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
if (!table)
return desc;
- for (p = &table->table[0]; p->chip_label; p++) {
+ for (p = &table->table[0]; p->key; p++) {
struct gpio_chip *chip;
/* idx must always match exactly */
@@ -4654,18 +4654,30 @@ static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
if (p->con_id && (!con_id || strcmp(p->con_id, con_id)))
continue;
- chip = find_chip_by_name(p->chip_label);
+ if (p->chip_hwnum == U16_MAX) {
+ desc = gpio_name_to_desc(p->key);
+ if (desc) {
+ *flags = p->flags;
+ return desc;
+ }
+
+ dev_warn(dev, "cannot find GPIO line %s, deferring\n",
+ p->key);
+ return ERR_PTR(-EPROBE_DEFER);
+ }
+
+ chip = find_chip_by_name(p->key);
if (!chip) {
/*
* As the lookup table indicates a chip with
- * p->chip_label should exist, assume it may
+ * p->key should exist, assume it may
* still appear later and let the interested
* consumer be probed again or let the Deferred
* Probe infrastructure handle the error.
*/
dev_warn(dev, "cannot find GPIO chip %s, deferring\n",
- p->chip_label);
+ p->key);
return ERR_PTR(-EPROBE_DEFER);
}
@@ -4696,7 +4708,7 @@ static int platform_gpio_count(struct device *dev, const char *con_id)
if (!table)
return -ENOENT;
- for (p = &table->table[0]; p->chip_label; p++) {
+ for (p = &table->table[0]; p->key; p++) {
if ((con_id && p->con_id && !strcmp(con_id, p->con_id)) ||
(!con_id && !p->con_id))
count++;
diff --git a/include/linux/gpio/machine.h b/include/linux/gpio/machine.h
index 1ebe5be05d5f81fa..84c66fbf54fd5811 100644
--- a/include/linux/gpio/machine.h
+++ b/include/linux/gpio/machine.h
@@ -20,8 +20,9 @@ enum gpio_lookup_flags {
/**
* struct gpiod_lookup - lookup table
- * @chip_label: name of the chip the GPIO belongs to
- * @chip_hwnum: hardware number (i.e. relative to the chip) of the GPIO
+ * @key: either the name of the chip the GPIO belongs to, or the GPIO line name
+ * @chip_hwnum: hardware number (i.e. relative to the chip) of the GPIO, or
+ * U16_MAX to indicate that @key is a GPIO line name
* @con_id: name of the GPIO from the device's point of view
* @idx: index of the GPIO in case several GPIOs share the same name
* @flags: bitmask of gpio_lookup_flags GPIO_* values
@@ -30,7 +31,7 @@ enum gpio_lookup_flags {
* functions using platform data.
*/
struct gpiod_lookup {
- const char *chip_label;
+ const char *key;
u16 chip_hwnum;
const char *con_id;
unsigned int idx;
@@ -63,17 +64,17 @@ struct gpiod_hog {
/*
* Simple definition of a single GPIO under a con_id
*/
-#define GPIO_LOOKUP(_chip_label, _chip_hwnum, _con_id, _flags) \
- GPIO_LOOKUP_IDX(_chip_label, _chip_hwnum, _con_id, 0, _flags)
+#define GPIO_LOOKUP(_key, _chip_hwnum, _con_id, _flags) \
+ GPIO_LOOKUP_IDX(_key, _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, _con_id, _idx, _flags) \
+#define GPIO_LOOKUP_IDX(_key, _chip_hwnum, _con_id, _idx, _flags) \
{ \
- .chip_label = _chip_label, \
+ .key = _key, \
.chip_hwnum = _chip_hwnum, \
.con_id = _con_id, \
.idx = _idx, \
--
2.17.1