[PATCH v3 1/1] gpiolib: of: add gpio-line node support
From: James Hilliard
Date: Mon Feb 16 2026 - 16:10:42 EST
Allow GPIO controller child nodes marked with "gpio-line" to apply
probe-time direction/flags without hogging the line.
Extend OF gpiochip scanning and OF dynamic reconfiguration handling to
process gpio-line nodes alongside gpio-hog nodes.
Some boards need probe-time GPIO direction/value setup while still
leaving lines available for later userspace or driver requests. GPIO
hogs can initialize lines but reserve them permanently.
Add gpiod_apply_line_init() as a core helper for one-shot line
initialization and use it for gpio-line setup.
Because gpio-line initialization does not reserve ownership, subsequent
consumer requests remain normal requests and may reconfigure or release
the line as usual.
Support "gpio-line-name" for setting the visible line name. For
gpio-hog nodes, keep "line-name" semantics as the hog consumer label.
Some boards only need to name a small subset of GPIO lines. Doing this
generally requires defining a full gpio-line-names array with empty
placeholders for unrelated lines.
In overlays, gpio-line-names replacement is all-or-nothing. Names from
base DT and multiple overlays for the same gpiochip do not compose,
because each update replaces the full property.
Signed-off-by: James Hilliard <james.hilliard1@xxxxxxxxx>
---
Depends on:
- https://github.com/devicetree-org/dt-schema/pull/185
Changes v1 -> v2:
- drop documentation changes
- add depends on to changelog
Changes v2 -> v3:
- add gpiod_apply_line_init() in gpiolib core
- switch gpio-line setup to use gpiod_apply_line_init()
---
drivers/gpio/gpiolib-of.c | 89 ++++++++++++++++++++++++++++-------
drivers/gpio/gpiolib-shared.c | 7 +--
drivers/gpio/gpiolib.c | 48 +++++++++++++++++++
drivers/gpio/gpiolib.h | 3 ++
drivers/of/property.c | 7 +--
scripts/dtc/checks.c | 4 +-
6 files changed, 133 insertions(+), 25 deletions(-)
diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index ef1ac68b94b7..5f531d5cbc00 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -744,6 +744,7 @@ struct gpio_desc *of_find_gpio(struct device_node *np, const char *con_id,
* @lflags: bitmask of gpio_lookup_flags GPIO_* values - returned from
* of_find_gpio() or of_parse_own_gpio()
* @dflags: gpiod_flags - optional GPIO initialization flags
+ * @hog: indicates if this is a gpio-hog node
*
* Returns:
* GPIO descriptor to use with Linux GPIO API, or one of the errno
@@ -753,11 +754,13 @@ static struct gpio_desc *of_parse_own_gpio(struct device_node *np,
struct gpio_chip *chip,
unsigned int idx, const char **name,
unsigned long *lflags,
- enum gpiod_flags *dflags)
+ enum gpiod_flags *dflags,
+ bool hog)
{
struct device_node *chip_np;
enum of_gpio_flags xlate_flags;
struct of_phandle_args gpiospec;
+ const char *desc_name;
struct gpio_desc *desc;
unsigned int i;
u32 tmp;
@@ -797,15 +800,19 @@ static struct gpio_desc *of_parse_own_gpio(struct device_node *np,
*dflags |= GPIOD_OUT_LOW;
else if (of_property_read_bool(np, "output-high"))
*dflags |= GPIOD_OUT_HIGH;
- else {
+ else if (hog) {
pr_warn("GPIO line %d (%pOFn): no hogging state specified, bailing out\n",
desc_to_gpio(desc), np);
return ERR_PTR(-EINVAL);
}
- if (name && of_property_read_string(np, "line-name", name))
+ if (hog && name && of_property_read_string(np, "line-name", name))
*name = np->name;
+ if (!of_property_read_string(np, "gpio-line-name", &desc_name) &&
+ desc_name[0])
+ desc->name = desc_name;
+
return desc;
}
@@ -827,7 +834,8 @@ static int of_gpiochip_add_hog(struct gpio_chip *chip, struct device_node *hog)
int ret;
for (i = 0;; i++) {
- desc = of_parse_own_gpio(hog, chip, i, &name, &lflags, &dflags);
+ desc = of_parse_own_gpio(hog, chip, i, &name, &lflags, &dflags,
+ true);
if (IS_ERR(desc))
break;
@@ -843,6 +851,36 @@ static int of_gpiochip_add_hog(struct gpio_chip *chip, struct device_node *hog)
return 0;
}
+/**
+ * of_gpiochip_add_line - Configure all lines in a gpio-line device node
+ * @chip: gpio chip to act on
+ * @line: device node describing GPIO lines to configure
+ *
+ * Returns:
+ * 0 on success, or negative errno on failure.
+ */
+static int of_gpiochip_add_line(struct gpio_chip *chip, struct device_node *line)
+{
+ enum gpiod_flags dflags;
+ struct gpio_desc *desc;
+ unsigned long lflags;
+ unsigned int i;
+ int ret;
+
+ for (i = 0;; i++) {
+ desc = of_parse_own_gpio(line, chip, i, NULL, &lflags, &dflags,
+ false);
+ if (IS_ERR(desc))
+ break;
+
+ ret = gpiod_apply_line_init(desc, NULL, lflags, dflags);
+ if (ret < 0)
+ return ret;
+ }
+
+ return 0;
+}
+
/**
* of_gpiochip_scan_gpios - Scan gpio-controller for gpio definitions
* @chip: gpio chip to act on
@@ -858,14 +896,22 @@ static int of_gpiochip_scan_gpios(struct gpio_chip *chip)
int ret;
for_each_available_child_of_node_scoped(dev_of_node(&chip->gpiodev->dev), np) {
- if (!of_property_read_bool(np, "gpio-hog"))
+ if (of_property_read_bool(np, "gpio-hog")) {
+ ret = of_gpiochip_add_hog(chip, np);
+ if (ret < 0)
+ return ret;
+
+ of_node_set_flag(np, OF_POPULATED);
continue;
+ }
- ret = of_gpiochip_add_hog(chip, np);
- if (ret < 0)
- return ret;
+ if (of_property_read_bool(np, "gpio-line")) {
+ ret = of_gpiochip_add_line(chip, np);
+ if (ret < 0)
+ return ret;
- of_node_set_flag(np, OF_POPULATED);
+ of_node_set_flag(np, OF_POPULATED);
+ }
}
return 0;
@@ -905,14 +951,15 @@ static int of_gpio_notify(struct notifier_block *nb, unsigned long action,
int ret;
/*
- * This only supports adding and removing complete gpio-hog nodes.
- * Modifying an existing gpio-hog node is not supported (except for
- * changing its "status" property, which is treated the same as
- * addition/removal).
+ * This only supports adding and removing complete gpio-hog and
+ * gpio-line nodes. Modifying an existing node is not supported
+ * (except for changing its "status" property, which is treated
+ * the same as addition/removal).
*/
switch (of_reconfig_get_state_change(action, arg)) {
case OF_RECONFIG_CHANGE_ADD:
- if (!of_property_read_bool(rd->dn, "gpio-hog"))
+ if (!of_property_read_bool(rd->dn, "gpio-hog") &&
+ !of_property_read_bool(rd->dn, "gpio-line"))
return NOTIFY_DONE; /* not for us */
if (of_node_test_and_set_flag(rd->dn, OF_POPULATED))
@@ -922,9 +969,12 @@ static int of_gpio_notify(struct notifier_block *nb, unsigned long action,
if (!gdev)
return NOTIFY_DONE; /* not for us */
- ret = of_gpiochip_add_hog(gpio_device_get_chip(gdev), rd->dn);
+ if (of_property_read_bool(rd->dn, "gpio-hog"))
+ ret = of_gpiochip_add_hog(gpio_device_get_chip(gdev), rd->dn);
+ else
+ ret = of_gpiochip_add_line(gpio_device_get_chip(gdev), rd->dn);
if (ret < 0) {
- pr_err("%s: failed to add hogs for %pOF\n", __func__,
+ pr_err("%s: failed to configure lines for %pOF\n", __func__,
rd->dn);
of_node_clear_flag(rd->dn, OF_POPULATED);
return notifier_from_errno(ret);
@@ -932,6 +982,10 @@ static int of_gpio_notify(struct notifier_block *nb, unsigned long action,
return NOTIFY_OK;
case OF_RECONFIG_CHANGE_REMOVE:
+ if (!of_property_read_bool(rd->dn, "gpio-hog") &&
+ !of_property_read_bool(rd->dn, "gpio-line"))
+ return NOTIFY_DONE; /* not for us */
+
if (!of_node_check_flag(rd->dn, OF_POPULATED))
return NOTIFY_DONE; /* already depopulated */
@@ -939,7 +993,8 @@ static int of_gpio_notify(struct notifier_block *nb, unsigned long action,
if (!gdev)
return NOTIFY_DONE; /* not for us */
- of_gpiochip_remove_hog(gpio_device_get_chip(gdev), rd->dn);
+ if (of_property_read_bool(rd->dn, "gpio-hog"))
+ of_gpiochip_remove_hog(gpio_device_get_chip(gdev), rd->dn);
of_node_clear_flag(rd->dn, OF_POPULATED);
return NOTIFY_OK;
}
diff --git a/drivers/gpio/gpiolib-shared.c b/drivers/gpio/gpiolib-shared.c
index b3525d1f06a4..b934e58a07f0 100644
--- a/drivers/gpio/gpiolib-shared.c
+++ b/drivers/gpio/gpiolib-shared.c
@@ -147,10 +147,11 @@ static bool gpio_shared_of_node_ignore(struct device_node *node)
return true;
/*
- * GPIO hogs have a "gpios" property which is not a phandle and can't
- * possibly refer to a shared GPIO.
+ * GPIO hog and gpio-line nodes have a "gpios" property which is not a
+ * phandle and can't possibly refer to a shared GPIO.
*/
- if (of_property_present(node, "gpio-hog"))
+ if (of_property_present(node, "gpio-hog") ||
+ of_property_present(node, "gpio-line"))
return true;
return false;
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index c52200eaaaff..e5ef2c0d8432 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -5061,6 +5061,54 @@ int gpiod_hog(struct gpio_desc *desc, const char *name,
return 0;
}
+/**
+ * gpiod_apply_line_init - Apply one-shot line initialization and release
+ * @desc: gpio whose value will be assigned
+ * @name: initialization label
+ * @lflags: bitmask of gpio_lookup_flags GPIO_* values
+ * @dflags: gpiod_flags - optional GPIO initialization flags
+ *
+ * Applies GPIO configuration using the descriptor APIs without keeping the line
+ * reserved by gpiolib. After configuration, the temporary internal request is
+ * released.
+ *
+ * Returns:
+ * 0 on success, or negative errno on failure.
+ */
+int gpiod_apply_line_init(struct gpio_desc *desc, const char *name,
+ unsigned long lflags, enum gpiod_flags dflags)
+{
+ struct gpio_device *gdev = desc->gdev;
+ struct gpio_desc *local_desc;
+ int hwnum;
+ int ret;
+
+ CLASS(gpio_chip_guard, guard)(desc);
+ if (!guard.gc)
+ return -ENODEV;
+
+ hwnum = gpiod_hwgpio(desc);
+
+ local_desc = gpiochip_request_own_desc(guard.gc, hwnum, name,
+ lflags, dflags);
+ if (IS_ERR(local_desc)) {
+ ret = PTR_ERR(local_desc);
+ pr_err("requesting init GPIO %s (chip %s, offset %d) failed, %d\n",
+ name ? : "?", gdev->label, hwnum, ret);
+ return ret;
+ }
+
+ gpiochip_free_own_desc(local_desc);
+
+ gpiod_dbg(desc, "line init applied as %s/%s\n",
+ !(dflags & GPIOD_FLAGS_BIT_DIR_SET) ? "as-is" :
+ (dflags & GPIOD_FLAGS_BIT_DIR_OUT) ? "output" : "input",
+ (dflags & GPIOD_FLAGS_BIT_DIR_OUT) ?
+ str_high_low(dflags & GPIOD_FLAGS_BIT_DIR_VAL) : "?");
+
+ return 0;
+}
+
/**
* gpiochip_free_hogs - Scan gpio-controller chip and release GPIO hog
* @gc: gpio chip to act on
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 3abb90385829..ed78f9d4d0af 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -271,6 +271,9 @@ int gpio_do_set_config(struct gpio_desc *desc, unsigned long config);
int gpiod_configure_flags(struct gpio_desc *desc, const char *con_id,
unsigned long lflags, enum gpiod_flags dflags);
int gpio_set_debounce_timeout(struct gpio_desc *desc, unsigned int debounce);
+int gpiod_apply_line_init(struct gpio_desc *desc,
+ const char *name, unsigned long lflags,
+ enum gpiod_flags dflags);
int gpiod_hog(struct gpio_desc *desc, const char *name,
unsigned long lflags, enum gpiod_flags dflags);
int gpiochip_get_ngpios(struct gpio_chip *gc, struct device *dev);
diff --git a/drivers/of/property.c b/drivers/of/property.c
index 50d95d512bf5..7689c4315115 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -1435,10 +1435,11 @@ static struct device_node *parse_gpio_compat(struct device_node *np,
return NULL;
/*
- * Ignore node with gpio-hog property since its gpios are all provided
- * by its parent.
+ * Ignore nodes with gpio-hog and gpio-line properties since their gpios
+ * are all provided by their parent.
*/
- if (of_property_read_bool(np, "gpio-hog"))
+ if (of_property_read_bool(np, "gpio-hog") ||
+ of_property_read_bool(np, "gpio-line"))
return NULL;
if (of_parse_phandle_with_args(np, prop_name, "#gpio-cells", index,
diff --git a/scripts/dtc/checks.c b/scripts/dtc/checks.c
index 45d0213f3bf3..ee64cb4ada4f 100644
--- a/scripts/dtc/checks.c
+++ b/scripts/dtc/checks.c
@@ -1533,8 +1533,8 @@ static void check_gpios_property(struct check *c,
{
struct property *prop;
- /* Skip GPIO hog nodes which have 'gpios' property */
- if (get_property(node, "gpio-hog"))
+ /* Skip gpio-hog and gpio-line nodes which have 'gpios' property */
+ if (get_property(node, "gpio-hog") || get_property(node, "gpio-line"))
return;
for_each_property(node, prop) {
--
2.43.0