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Subject[PATCH 02/24] leds: core: Add support for composing LED class device names
Date
Add public led_compose_name() API for composing LED class device
name basing on fwnode_handle data. The function composes device name
according to either a new <color:function> pattern or the legacy
<devicename:color:function> pattern. The decision on using the
particular pattern is made basing on whether fwnode contains new
"function" and "color" properties, or the legacy "label" proeprty.

Backwards compatibility with in-driver hard-coded LED class device
names is assured thanks to the default_desc argument.

In case none of the aformentioned properties was found, then, for OF
nodes, the node name is adopted for LED class device name.

Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Baolin Wang <baolin.wang@linaro.org>
Cc: Daniel Mack <daniel@zonque.org>
Cc: Dan Murphy <dmurphy@ti.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Oleh Kravchenko <oleg@kaa.org.ua>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: Simon Shields <simon@lineageos.org>
Cc: Xiaotong Lu <xiaotong.lu@spreadtrum.com>
---
Documentation/leds/leds-class.txt | 2 +-
drivers/leds/led-core.c | 71 +++++++++++++++++++++++++++++++++++++++
include/linux/leds.h | 32 ++++++++++++++++++
3 files changed, 104 insertions(+), 1 deletion(-)

diff --git a/Documentation/leds/leds-class.txt b/Documentation/leds/leds-class.txt
index 836cb16..e9009c4 100644
--- a/Documentation/leds/leds-class.txt
+++ b/Documentation/leds/leds-class.txt
@@ -43,7 +43,7 @@ LED Device Naming

Is currently of the form:

-"devicename:colour:function"
+"colour:function"

There have been calls for LED properties such as colour to be exported as
individual led class attributes. As a solution which doesn't incur as much
diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index ede4fa0..f7371fc 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -16,6 +16,8 @@
#include <linux/list.h>
#include <linux/module.h>
#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/property.h>
#include <linux/rwsem.h>
#include "leds.h"

@@ -327,3 +329,72 @@ void led_sysfs_enable(struct led_classdev *led_cdev)
led_cdev->flags &= ~LED_SYSFS_DISABLE;
}
EXPORT_SYMBOL_GPL(led_sysfs_enable);
+
+static void led_parse_properties(struct fwnode_handle *fwnode,
+ struct led_properties *props)
+{
+ int ret;
+
+ if (!fwnode)
+ return;
+
+ ret = fwnode_property_read_string(fwnode, "label", &props->label);
+ if (!ret)
+ return;
+
+ ret = fwnode_property_read_string(fwnode, "function", &props->function);
+ if (ret)
+ pr_info("Failed to parse function property\n");
+
+ ret = fwnode_property_read_string(fwnode, "color", &props->color);
+ if (ret)
+ pr_info("Failed to parse color property\n");
+}
+
+int led_compose_name(struct fwnode_handle *fwnode, const char *led_hw_name,
+ const char *default_desc, char *led_classdev_name)
+{
+ struct led_properties props = {};
+
+ if (!led_classdev_name)
+ return -EINVAL;
+
+ led_parse_properties(fwnode, &props);
+
+ if (props.label) {
+ /*
+ * Presence of 'label' DT property implies legacy LED name,
+ * formatted as <devicename:color:function>, with possible
+ * section omission if doesn't apply to given device.
+ *
+ * If no led_hw_name has been passed, then it indicates that
+ * DT label should be used as-is for LED class device name.
+ * Otherwise the label is prepended with led_hw_name to compose
+ * the final LED class device name.
+ */
+ if (!led_hw_name) {
+ strncpy(led_classdev_name, props.label,
+ LED_MAX_NAME_SIZE);
+ } else {
+ snprintf(led_classdev_name, LED_MAX_NAME_SIZE, "%s:%s",
+ led_hw_name, props.label);
+ }
+ } else if (props.function || props.color) {
+ snprintf(led_classdev_name, LED_MAX_NAME_SIZE, "%s:%s",
+ props.color ?: "", props.function ?: "");
+ } else if (default_desc) {
+ if (!led_hw_name) {
+ pr_err("Legacy LED naming requires devicename segment");
+ return -EINVAL;
+ }
+ snprintf(led_classdev_name, LED_MAX_NAME_SIZE, "%s:%s",
+ led_hw_name, default_desc);
+ } else if (is_of_node(fwnode)) {
+ strncpy(led_classdev_name, to_of_node(fwnode)->name,
+ LED_MAX_NAME_SIZE);
+ } else
+ return -EINVAL;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(led_compose_name);
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 646c49a..ddb4001 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -238,6 +238,32 @@ extern void led_sysfs_disable(struct led_classdev *led_cdev);
extern void led_sysfs_enable(struct led_classdev *led_cdev);

/**
+ * led_compose_name - compose LED class device name
+ * @child: child fwnode_handle describing a LED,
+ * or a group of synchronized LEDs.
+ * @led_hw_name: name of the LED controller, used when falling back to legacy
+ * LED naming; it should be set to NULL in new LED class drivers
+ * @default_desc: default <color:function> tuple, for backwards compatibility
+ * with in-driver hard-coded LED names used as a fallback when
+ * "label" DT property was absent; it should be set to NULL
+ * in new LED class drivers
+ * @led_classdev_name: composed LED class device name
+ *
+ * Create LED class device name basing on the configuration provided by the
+ * board firmware. The name can have a legacy form <devicename:color:function>,
+ * or a new form <color:function>. The latter is chosen if at least one of
+ * "color" or "function" properties is present in the fwnode, leaving the
+ * section blank if the related property is absent. The former is applied
+ * when legacy "label" property is present in the fwnode. In case none of the
+ * aformentioned properties was found, then, for OF nodes, the node name
+ * is adopted for LED class device name.
+ *
+ * Returns: 0 on success or negative error value on failure
+ */
+extern int led_compose_name(struct fwnode_handle *child, const char *led_hw_name,
+ const char *default_desc, char *led_classdev_name);
+
+/**
* led_sysfs_is_disabled - check if LED sysfs interface is disabled
* @led_cdev: the LED to query
*
@@ -414,6 +440,12 @@ struct led_platform_data {
struct led_info *leds;
};

+struct led_properties {
+ const char *color;
+ const char *function;
+ const char *label;
+};
+
struct gpio_desc;
typedef int (*gpio_blink_set_t)(struct gpio_desc *desc, int state,
unsigned long *delay_on,
--
2.1.4
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