[PATCH v4 05/10] gpiolib: support shared GPIOs in core subsystem code

Bartosz Golaszewski
2025-11-12T13:55:49Z

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

As the final step in adding official support for shared GPIOs, enable
the previously added elements in core GPIO subsystem code. Set-up shared
GPIOs when adding a GPIO chip, tear it down on removal and check if a
GPIO descriptor looked up during the firmware-node stage is shared and
fall-back to machine lookup in this case.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
drivers/gpio/gpiolib.c | 50 +++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 41 insertions(+), 9 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 3659acc600d9622d5d2baeb055ac083556f344a9..c59fe05c838e073b4bc99c4a7667cb1ff40c26b4 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -37,6 +37,7 @@
#include "gpiolib-acpi.h"
#include "gpiolib-cdev.h"
#include "gpiolib-of.h"
+#include "gpiolib-shared.h"
#include "gpiolib-swnode.h"
#include "gpiolib-sysfs.h"
#include "gpiolib.h"
@@ -1213,6 +1214,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
if (ret)
goto err_remove_irqchip_mask;

+ ret = gpio_device_setup_shared(gdev);
+ if (ret)
+ goto err_remove_irqchip;
+
/*
* By first adding the chardev, and then adding the device,
* we get a device node entry in sysfs under
@@ -1224,10 +1229,13 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
if (gpiolib_initialized) {
ret = gpiochip_setup_dev(gdev);
if (ret)
- goto err_remove_irqchip;
+ goto err_teardown_shared;
}
+
return 0;

+err_teardown_shared:
+ gpio_device_teardown_shared(gdev);
err_remove_irqchip:
gpiochip_irqchip_remove(gc);
err_remove_irqchip_mask:
@@ -1296,6 +1304,7 @@ void gpiochip_remove(struct gpio_chip *gc)
/* Numb the device, cancelling all outstanding operations */
rcu_assign_pointer(gdev->chip, NULL);
synchronize_srcu(&gdev->srcu);
+ gpio_device_teardown_shared(gdev);
gpiochip_irqchip_remove(gc);
acpi_gpiochip_remove(gc);
of_gpiochip_remove(gc);
@@ -4659,11 +4668,29 @@ struct gpio_desc *gpiod_find_and_request(struct device *consumer,
scoped_guard(srcu, &gpio_devices_srcu) {
desc = gpiod_fwnode_lookup(fwnode, consumer, con_id, idx,
&flags, &lookupflags);
+ if (!IS_ERR_OR_NULL(desc) &&
+ test_bit(GPIOD_FLAG_SHARED, &desc->flags)) {
+ /*
+ * We're dealing with a GPIO shared by multiple
+ * consumers. This is the moment to add the machine
+ * lookup table for the proxy device as previously
+ * we only knew the consumer's fwnode.
+ */
+ ret = gpio_shared_add_proxy_lookup(consumer, lookupflags);
+ if (ret)
+ return ERR_PTR(ret);
+
+ /* Trigger platform lookup for shared GPIO proxy. */
+ desc = ERR_PTR(-ENOENT);
+ /* Trigger it even for fwnode-only gpiod_get(). */
+ platform_lookup_allowed = true;
+ }
+
if (gpiod_not_found(desc) && platform_lookup_allowed) {
/*
* Either we are not using DT or ACPI, or their lookup
- * did not return a result. In that case, use platform
- * lookup as a fallback.
+ * did not return a result or this is a shared GPIO. In
+ * that case, use platform lookup as a fallback.
*/
dev_dbg(consumer,
"using lookup tables for GPIO lookup\n");
@@ -4686,14 +4713,19 @@ struct gpio_desc *gpiod_find_and_request(struct device *consumer,
return ERR_PTR(ret);

/*
- * This happens when there are several consumers for
- * the same GPIO line: we just return here without
- * further initialization. It is a bit of a hack.
- * This is necessary to support fixed regulators.
+ * This happens when there are several consumers for the same
+ * GPIO line: we just return here without further
+ * initialization. It's a hack introduced long ago to support
+ * fixed regulators. We now have a better solution with
+ * automated scanning where affected platforms just need to
+ * select the provided Kconfig option.
*
- * FIXME: Make this more sane and safe.
+ * FIXME: Remove the GPIOD_FLAGS_BIT_NONEXCLUSIVE flag after
+ * making sure all platforms use the new mechanism.
*/
- dev_info(consumer, "nonexclusive access to GPIO for %s\n", name);
+ dev_info(consumer,
+ "nonexclusive access to GPIO for %s, consider updating your code to using gpio-shared-proxy\n",
+ name);
return desc;
}

--
2.51.0