leds: turris-omnia: Notify sysfs on MCU global LEDs brightness change

Recall that on Turris Omnia, the LED controller has a global brightness
property, which allows the user to make the front LED panel dimmer.

There is also a button on the front panel, which by default is
configured so that pressing it changes the global brightness to a lower
value (unless it is at 0%, in which case pressing the button changes the
global brightness to 100%).

Newer versions of the MCU firmware support informing the SOC that the
brightness was changed by button press event via an interrupt.

Now that we have the turris-omnia-mcu driver, which adds support for MCU
interrupts, add the ability to inform the userspace (via a sysfs
notification) that the global brightness was changed.

Signed-off-by: Marek Behún <kabel@kernel.org>
Link: https://lore.kernel.org/r/20241111100355.6978-8-kabel@kernel.org
Signed-off-by: Lee Jones <lee@kernel.org>

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index fcbe93b61e49855388708bdc9cd85b438f023c4a..9ab6b56898c67675e9e3599f258077fb7a81b21a 100644 (file)
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -218,6 +218,7 @@ config LEDS_TURRIS_OMNIA
        depends on MACH_ARMADA_38X || COMPILE_TEST
        depends on OF
        depends on TURRIS_OMNIA_MCU
+       depends on TURRIS_OMNIA_MCU_GPIO
        select LEDS_TRIGGERS
        help
          This option enables basic support for the LEDs found on the front

diff --git a/drivers/leds/leds-turris-omnia.c b/drivers/leds/leds-turris-omnia.c
index 83a011e5259c1eb85f56c9cebd93df5f848dcd32..4f7b529781ce7cfb90f786a7a8adccec93990ac7 100644 (file)
--- a/drivers/leds/leds-turris-omnia.c
+++ b/drivers/leds/leds-turris-omnia.c
@@ -42,12 +42,15 @@ struct omnia_led {
  * @client:                    I2C client device
  * @lock:                      mutex to protect cached state
  * @has_gamma_correction:      whether the MCU firmware supports gamma correction
+ * @brightness_knode:          kernel node of the "brightness" device sysfs attribute (this is the
+ *                             driver specific global brightness, not the LED classdev brightness)
  * @leds:                      flexible array of per-LED data
  */
 struct omnia_leds {
        struct i2c_client *client;
        struct mutex lock;
        bool has_gamma_correction;
+       struct kernfs_node *brightness_knode;
        struct omnia_led leds[];
 };
 
@@ -372,6 +375,59 @@ static struct attribute *omnia_led_controller_attrs[] = {
 };
 ATTRIBUTE_GROUPS(omnia_led_controller);
 
+static irqreturn_t omnia_brightness_changed_threaded_fn(int irq, void *data)
+{
+       struct omnia_leds *leds = data;
+
+       if (unlikely(!leds->brightness_knode)) {
+               /*
+                * Note that sysfs_get_dirent() may sleep. This is okay, because we are in threaded
+                * context.
+                */
+               leds->brightness_knode = sysfs_get_dirent(leds->client->dev.kobj.sd, "brightness");
+               if (!leds->brightness_knode)
+                       return IRQ_NONE;
+       }
+
+       sysfs_notify_dirent(leds->brightness_knode);
+
+       return IRQ_HANDLED;
+}
+
+static void omnia_brightness_knode_put(void *data)
+{
+       struct omnia_leds *leds = data;
+
+       if (leds->brightness_knode)
+               sysfs_put(leds->brightness_knode);
+}
+
+static int omnia_request_brightness_irq(struct omnia_leds *leds)
+{
+       struct device *dev = &leds->client->dev;
+       int ret;
+
+       if (!leds->client->irq) {
+               dev_info(dev,
+                        "Brightness change interrupt supported by MCU firmware but not described in device-tree\n");
+
+               return 0;
+       }
+
+       /*
+        * Registering the brightness_knode destructor before requesting the IRQ ensures that on
+        * removal the brightness_knode sysfs node is put only after the IRQ is freed.
+        * This is needed because the interrupt handler uses the knode.
+        */
+       ret = devm_add_action(dev, omnia_brightness_knode_put, leds);
+       if (ret < 0)
+               return ret;
+
+       return devm_request_threaded_irq(dev, leds->client->irq, NULL,
+                                        omnia_brightness_changed_threaded_fn, IRQF_ONESHOT,
+                                        "leds-turris-omnia", leds);
+}
+
 static int omnia_mcu_get_features(const struct i2c_client *mcu_client)
 {
        u16 reply;
@@ -458,6 +514,12 @@ static int omnia_leds_probe(struct i2c_client *client)
                         "Consider upgrading MCU firmware with the omnia-mcutool utility.\n");
        }
 
+       if (ret & OMNIA_FEAT_BRIGHTNESS_INT) {
+               ret = omnia_request_brightness_irq(leds);
+               if (ret < 0)
+                       return dev_err_probe(dev, ret, "Cannot request brightness IRQ\n");
+       }
+
        mutex_init(&leds->lock);
 
        ret = devm_led_trigger_register(dev, &omnia_hw_trigger);