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Message-Id: <20251022-gpio-shared-v2-6-d34aa1fbdf06@linaro.org>
Date: Wed, 22 Oct 2025 15:10:45 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Kees Cook <kees@...nel.org>, Mika Westerberg <westeri@...nel.org>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Walleij <linus.walleij@...aro.org>,
Manivannan Sadhasivam <mani@...nel.org>, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Saravana Kannan <saravanak@...gle.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Andy Shevchenko <andy@...nel.org>, Bartosz Golaszewski <brgl@...ev.pl>,
Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
Srinivas Kandagatla <srini@...nel.org>, Liam Girdwood <lgirdwood@...il.com>,
Mark Brown <broonie@...nel.org>, Jaroslav Kysela <perex@...ex.cz>,
Takashi Iwai <tiwai@...e.com>
Cc: linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-gpio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-sound@...r.kernel.org, linux-arm-msm@...r.kernel.org,
Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH v2 06/10] gpio: provide gpiod_is_shared()
From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Provide an interface allowing consumers to check if a GPIO descriptor
represents a GPIO that can potentially be shared by multiple consumers
at the same time. This is exposed to allow subsystems that already
work around the limitations of the current non-exclusive GPIO handling
in some ways, to gradually convert to relying on the new shared GPIO
feature of GPIOLIB.
Extend the gpiolib-shared module to mark the GPIO shared proxy
descriptors with a flag checked by the new interface.
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
drivers/gpio/gpiolib-shared.c | 18 ++++++++++++++++++
drivers/gpio/gpiolib.c | 20 ++++++++++++++++++++
drivers/gpio/gpiolib.h | 1 +
include/linux/gpio/consumer.h | 9 +++++++++
4 files changed, 48 insertions(+)
diff --git a/drivers/gpio/gpiolib-shared.c b/drivers/gpio/gpiolib-shared.c
index d2087d0df4ab7bcd23d3736e341c0f57cd748af4..b5c33bccff0765eb940fedd5d678c47a05f1a25d 100644
--- a/drivers/gpio/gpiolib-shared.c
+++ b/drivers/gpio/gpiolib-shared.c
@@ -309,6 +309,24 @@ int gpio_device_setup_shared(struct gpio_device *gdev)
guard(mutex)(&gpio_shared_lock);
+ list_for_each_entry(entry, &gpio_shared_list, list) {
+ list_for_each_entry(ref, &entry->refs, list) {
+ if (gdev->dev.parent == &ref->adev.dev) {
+ /*
+ * This is a shared GPIO proxy. Mark its
+ * descriptor as such and return here.
+ */
+ set_bit(GPIOD_FLAG_SHARED_PROXY,
+ &gdev->descs[0].flags);
+ return 0;
+ }
+ }
+ }
+
+ /*
+ * This is not a shared GPIO proxy but it still may be the device
+ * exposing shared pins. Find them and create the proxy devices.
+ */
list_for_each_entry(entry, &gpio_shared_list, list) {
if (!device_match_fwnode(&gdev->dev, entry->fwnode))
continue;
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 03fd60e787fcf5846519fb2db9a701770ed15d6b..d689065471a1269ac0671b964c67670df5c95dd7 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -3984,6 +3984,26 @@ int gpiod_set_consumer_name(struct gpio_desc *desc, const char *name)
}
EXPORT_SYMBOL_GPL(gpiod_set_consumer_name);
+/**
+ * gpiod_is_shared() - check if this GPIO can be shared by multiple consumers
+ * @desc: GPIO to inspect
+ *
+ * Returns:
+ * True if this GPIO can be shared by multiple consumers at once. False if it's
+ * a regular, exclusive GPIO.
+ *
+ * Note:
+ * This function returning true does not mean that this GPIO is currently being
+ * shared. It means the GPIO core has registered the fact that the firmware
+ * configuration indicates that it can be shared by multiple consumers and is
+ * in charge of arbitrating the access.
+ */
+bool gpiod_is_shared(const struct gpio_desc *desc)
+{
+ return test_bit(GPIOD_FLAG_SHARED_PROXY, &desc->flags);
+}
+EXPORT_SYMBOL_GPL(gpiod_is_shared);
+
/**
* gpiod_to_irq() - return the IRQ corresponding to a GPIO
* @desc: gpio whose IRQ will be returned (already requested)
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index ae9aa145ca055c08dad55a537567a27de57f7066..8deed8a7d1128f01f0696af040d06f5fe140c7f8 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -205,6 +205,7 @@ struct gpio_desc {
#define GPIOD_FLAG_EVENT_CLOCK_REALTIME 18 /* GPIO CDEV reports REALTIME timestamps in events */
#define GPIOD_FLAG_EVENT_CLOCK_HTE 19 /* GPIO CDEV reports hardware timestamps in events */
#define GPIOD_FLAG_SHARED 20 /* GPIO is shared by multiple consumers */
+#define GPIOD_FLAG_SHARED_PROXY 21 /* GPIO is a virtual proxy to a physically shared pin. */
/* Connection label */
struct gpio_desc_label __rcu *label;
diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h
index 00df68c514051434e6fa67dc2307c6a8ce4ce3df..a8acb7c0b5af5066fd05e533468fc28616c68d78 100644
--- a/include/linux/gpio/consumer.h
+++ b/include/linux/gpio/consumer.h
@@ -167,6 +167,8 @@ int gpiod_cansleep(const struct gpio_desc *desc);
int gpiod_to_irq(const struct gpio_desc *desc);
int gpiod_set_consumer_name(struct gpio_desc *desc, const char *name);
+bool gpiod_is_shared(const struct gpio_desc *desc);
+
/* Convert between the old gpio_ and new gpiod_ interfaces */
struct gpio_desc *gpio_to_desc(unsigned gpio);
int desc_to_gpio(const struct gpio_desc *desc);
@@ -520,6 +522,13 @@ static inline int gpiod_set_consumer_name(struct gpio_desc *desc,
return -EINVAL;
}
+static inline bool gpiod_is_shared(const struct gpio_desc *desc)
+{
+ /* GPIO can never have been requested */
+ WARN_ON(desc);
+ return false;
+}
+
static inline struct gpio_desc *gpio_to_desc(unsigned gpio)
{
return NULL;
--
2.48.1
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