Re: [PATCH net-next + leds v2 2/7] leds: add generic API for LEDs that can be controlled by hardware

On Wed, 9 Sep 2020 11:20:00 -0700
Randy Dunlap [off-list ref] wrote:

Hi,

On 9/9/20 9:25 AM, Marek Behún wrote:

quoted

Many an ethernet PHY (and other chips) supports various HW control
modes for LEDs connected directly to them.

This patch adds a generic API for registering such LEDs when
described in device tree. This API also exposes generic way to
select between these hardware control modes.

This API registers a new private LED trigger called dev-hw-mode.
When this trigger is enabled for a LED, the various HW control
modes which are supported by the device for given LED can be
get/set via hw_mode sysfs file.

Signed-off-by: Marek Behún <redacted>
---
 .../sysfs-class-led-trigger-dev-hw-mode       |   8 +
 drivers/leds/Kconfig                          |  10 +
 drivers/leds/Makefile                         |   1 +
 drivers/leds/leds-hw-controlled.c             | 227
++++++++++++++++++ include/linux/leds-hw-controlled.h            |
74 ++++++ 5 files changed, 320 insertions(+)
 create mode 100644
Documentation/ABI/testing/sysfs-class-led-trigger-dev-hw-mode
create mode 100644 drivers/leds/leds-hw-controlled.c create mode
100644 include/linux/leds-hw-controlled.h 

quoted

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 1c181df24eae4..5e47ab21aafb4 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig

@@ -49,6 +49,16 @@ config LEDS_BRIGHTNESS_HW_CHANGED
 
 	  See Documentation/ABI/testing/sysfs-class-led for

details. 
+config LEDS_HW_CONTROLLED
+	bool "API for LEDs that can be controlled by hardware"
+	depends on LEDS_CLASS  

	depends on OF || COMPILE_TEST
?

I specifically did not add OF dependency so that this can be also used
on non-OF systems. A device driver may register such LED itself...
That's why hw_controlled_led_brightness_set symbol is exported.

Do you think I shouldn't do it?

quoted

+	select LEDS_TRIGGERS
+	help
+	  This option enables support for a generic API via which
other drivers
+	  can register LEDs that can be put into hardware
controlled mode, eg.  

	                                                                   e.g.

This will need to be changed on multiple places, thanks.

quoted

+	  a LED connected to an ethernet PHY can be configured to
blink on  

	  an LED

This as well

quoted

+	  network activity.
+
 comment "LED drivers"
 
 config LEDS_88PM860X  

quoted

diff --git a/include/linux/leds-hw-controlled.h

b/include/linux/leds-hw-controlled.h new file mode 100644
index 0000000000000..2c9b8a06def18

--- /dev/null
+++ b/include/linux/leds-hw-controlled.h

@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Generic API for LEDs that can be controlled by hardware (eg. by

an ethernet PHY chip)
+ *
+ * Copyright (C) 2020 Marek Behun [off-list ref]
+ */
+#ifndef _LINUX_LEDS_HW_CONTROLLED_H_
+#define _LINUX_LEDS_HW_CONTROLLED_H_
+
+#include <linux/kernel.h>
+#include <linux/leds.h>
+
+struct hw_controlled_led {
+	struct led_classdev cdev;
+	const struct hw_controlled_led_ops *ops;
+	struct mutex lock;
+
+	/* these members are filled in by OF if OF is enabled */
+	int addr;
+	bool active_low;
+	bool tristate;
+
+	/* also filled in by OF, but changed by led_set_hw_mode
operation */
+	const char *hw_mode;
+
+	void *priv;
+};
+#define led_cdev_to_hw_controlled_led(l) container_of(l, struct
hw_controlled_led, cdev) +
+/* struct hw_controlled_led_ops: Operations on LEDs that can be
controlled by HW
+ *
+ * All the following operations must be implemented:
+ * @led_init: Should initialize the LED from OF data (and sanity
check whether they are correct).
+ *            This should also change led->cdev.max_brightness, if
the value differs from default,
+ *            which is 1.
+ * @led_brightness_set: Sets brightness.
+ * @led_iter_hw_mode: Iterates available HW control mode names for
this LED.
+ * @led_set_hw_mode: Sets HW control mode to value specified by
given name.
+ * @led_get_hw_mode: Returns current HW control mode name.
+ */  

Convert that struct info to kernel-doc?

Will look into this.
Thanks.

quoted

+struct hw_controlled_led_ops {
+	int (*led_init)(struct device *dev, struct
hw_controlled_led *led);
+	int (*led_brightness_set)(struct device *dev, struct
hw_controlled_led *led,
+				  enum led_brightness brightness);
+	const char *(*led_iter_hw_mode)(struct device *dev, struct
hw_controlled_led *led,
+					void **iter);
+	int (*led_set_hw_mode)(struct device *dev, struct
hw_controlled_led *led,
+			       const char *mode);
+	const char *(*led_get_hw_mode)(struct device *dev, struct
hw_controlled_led *led); +};
+  

quoted

+
+#endif /* _LINUX_LEDS_HW_CONTROLLED_H_ */  

thanks.