[RFC PATCH v2 2/5] leds: add function to configure offload leds

[Ansuel Smith <ansuelsmth@gmail.com>]

Add configure_offload helper to configure how the LED should work in
offload mode. The function require to support the particular trigger and
will use the passed offload_flags to elaborate the data and apply the
correct configuration. This function will then be used by the offload
trigger to request and update offload configuration.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
---
 Documentation/leds/leds-class.rst | 24 ++++++++++++++++++++++++
 include/linux/leds.h              | 28 ++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/Documentation/leds/leds-class.rst b/Documentation/leds/leds-class.rst
index 5bf6e5d471ce..0a3bbe71dac7 100644
--- a/Documentation/leds/leds-class.rst
+++ b/Documentation/leds/leds-class.rst
@@ -190,6 +190,30 @@ If the second argument (enable) to the trigger_offload() method is false, any
 active HW offloading must be deactivated. In this case errors are not permitted
 in the trigger_offload() method and the driver will be set to the new trigger.
 
+The offload trigger will use the function configure_offload() provided by the driver
+that will configure the offloaded mode for the LED.
+This function passes as the first argument (offload_flags) a u32 flag.
+The second argument (cmd) of the configure_offload() method can be used to do various
+operations for the specific trigger. We currently support ENABLE, DISABLE, READ and
+SUPPORTED to enable, disable, read the state of the offload trigger and ask the LED
+driver supports the specific offload trigger.
+
+In ENABLE/DISABLE configure_offload() should configure the LED to enable/disable the
+requested trigger (flags).
+In READ configure_offload() should return 0 or 1 based on the status of the requested
+trigger (flags).
+In SUPPORTED configure_offload() should return 0 or 1 if the LED driver supports the
+requested trigger (flags) or not.
+
+The u32 flag is specific to the trigger and change across them. It's in the LED
+driver interest know how to elaborate this flag and to declare support for a
+particular offload trigger. For this exact reason explicit support for the specific
+trigger is mandatory or the driver returns -EOPNOTSUPP if asked to enter offload mode
+with a not supported trigger.
+If the driver returns -EOPNOTSUPP on configure_offload(), the trigger activation will
+fail as the driver doesn't support that specific offload trigger or doesn't know
+how to handle the provided flags.
+
 Known Issues
 ============
 
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 949ab461287f..2a1e60e4d73e 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -67,6 +67,15 @@ struct led_hw_trigger_type {
 	int dummy;
 };
 
+#ifdef CONFIG_LEDS_OFFLOAD_TRIGGERS
+enum offload_trigger_cmd {
+	TRIGGER_ENABLE, /* Enable the offload trigger */
+	TRIGGER_DISABLE, /* Disable the offload trigger */
+	TRIGGER_READ, /* Read the status of the offload trigger */
+	TRIGGER_SUPPORTED, /* Ask the driver if the trigger is supported */
+};
+#endif
+
 struct led_classdev {
 	const char		*name;
 	unsigned int brightness;
@@ -160,6 +169,14 @@ struct led_classdev {
 	/* some LEDs cne be driven by HW */
 	int			(*trigger_offload)(struct led_classdev *led_cdev,
 						   bool enable);
+	/* Function to configure how the LEDs should work in offload mode.
+	 * The function require to support the trigger and will use the
+	 * passed flags to elaborate the trigger requested and apply the
+	 * correct configuration.
+	 */
+	int			(*configure_offload)(struct led_classdev *led_cdev,
+						     u32 offload_flags,
+						     enum offload_trigger_cmd cmd);
 #endif
 #endif
 
@@ -417,6 +434,17 @@ static inline void *led_get_trigger_data(struct led_classdev *led_cdev)
 }
 
 #ifdef CONFIG_LEDS_OFFLOAD_TRIGGERS
+bool led_trigger_offload_is_supported(struct led_classdev *led_cdev, u32 flags)
+{
+	int ret;
+
+	ret = led_cdev->configure_offload(led_cdev, flags, TRIGGER_SUPPORTED);
+	if (ret > 0)
+		return true;
+
+	return false;
+}
+
 static inline int led_trigger_offload(struct led_classdev *led_cdev)
 {
 	int ret;
-- 
2.32.0