[PATCH v3 1/1] gpiolib: of: add gpio-line node support
From: James Hilliard <hidden>
Date: 2026-02-16 21:10:28
Also in:
linux-gpio, lkml
Subsystem:
gpio subsystem, open firmware and flattened device tree, the rest · Maintainers:
Linus Walleij, Bartosz Golaszewski, Rob Herring, Saravana Kannan, Linus Torvalds
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 <redacted> --- 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