linux-kernel - [PATCH v2] gpiolib: notify user-space about line state changes triggered by kernel

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Date:   Thu, 24 Aug 2023 10:55:44 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Kent Gibson <warthog618@...il.com>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH v2] gpiolib: notify user-space about line state changes triggered by kernel

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

We currently only emit CHANGED_CONFIG events when the user-space changes
GPIO config. We won't be notified if changes come from in-kernel. Let's
call the notifier chain whenever kernel users change direction or any of
the active-low, debounce or consumer name settings. We don't notify the
user-space about the persistence as the uAPI has no notion of it.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
v1 -> v2:
- use the gpiod_line_state_notify() helper
- reorder the code in gpiod_set_debounce() for better readability

 drivers/gpio/gpiolib.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 40a0022ea719..1cb7731550ca 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2439,6 +2439,7 @@ int gpiod_direction_input(struct gpio_desc *desc)
 	}
 	if (ret == 0) {
 		clear_bit(FLAG_IS_OUT, &desc->flags);
+		gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_CONFIG);
 		ret = gpio_set_bias(desc);
 	}
 
@@ -2484,8 +2485,10 @@ static int gpiod_direction_output_raw_commit(struct gpio_desc *desc, int value)
 		gc->set(gc, gpio_chip_hwgpio(desc), val);
 	}
 
-	if (!ret)
+	if (!ret) {
 		set_bit(FLAG_IS_OUT, &desc->flags);
+		gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_CONFIG);
+	}
 	trace_gpio_value(desc_to_gpio(desc), 0, val);
 	trace_gpio_direction(desc_to_gpio(desc), 0, ret);
 	return ret;
@@ -2672,9 +2675,16 @@ EXPORT_SYMBOL_GPL(gpiod_set_config);
 int gpiod_set_debounce(struct gpio_desc *desc, unsigned int debounce)
 {
 	unsigned long config;
+	int ret;
 
 	config = pinconf_to_config_packed(PIN_CONFIG_INPUT_DEBOUNCE, debounce);
-	return gpiod_set_config(desc, config);
+	ret = gpiod_set_config(desc, config);
+	if (ret)
+		return ret;
+
+	gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_CONFIG);
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(gpiod_set_debounce);
 
@@ -2723,6 +2733,7 @@ void gpiod_toggle_active_low(struct gpio_desc *desc)
 {
 	VALIDATE_DESC_VOID(desc);
 	change_bit(FLAG_ACTIVE_LOW, &desc->flags);
+	gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_CONFIG);
 }
 EXPORT_SYMBOL_GPL(gpiod_toggle_active_low);
 
@@ -3330,6 +3341,7 @@ int gpiod_set_consumer_name(struct gpio_desc *desc, const char *name)
 
 	kfree_const(desc->label);
 	desc_set_label(desc, name);
+	gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_CONFIG);
 
 	return 0;
 }
-- 
2.39.2