[PATCH v5 04/19] backlight: improve backlight_properties documentation

Sam Ravnborg
2020-07-19T08:08:11Z

Improve the documentation for backlight_properties and
adapt it to kernel-doc style.

v3:
- Added missing '@' in kernel-doc

v2:
- Added into for each field (Daniel)
- Re-written some parts to explain what to do, rather
than what not to do.
Partly based on suggestions from the review (Daniel)

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jingoo Han <jingoohan1@gmail.com>
---
include/linux/backlight.h | 96 ++++++++++++++++++++++++++++++++++-----
1 file changed, 85 insertions(+), 11 deletions(-)

diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index dfb43ee02ea0..10518b00b059 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -117,28 +117,102 @@ struct backlight_ops {
int (*check_fb)(struct backlight_device *bd, struct fb_info *info);
};

-/* This structure defines all the properties of a backlight */
+/**
+ * struct backlight_properties - backlight properties
+ *
+ * This structure defines all the properties of a backlight.
+ */
struct backlight_properties {
- /* Current User requested brightness (0 - max_brightness) */
+ /**
+ * @brightness: The current brightness requested by the user.
+ *
+ * The backlight core makes sure the range is (0 to max_brightness)
+ * when the brightness is set via the sysfs attribute:
+ * /sys/class/backlight/<backlight>/brightness.
+ *
+ * This value can be set in the backlight_properties passed
+ * to devm_backlight_device_register() to set a default brightness
+ * value.
+ */
int brightness;
- /* Maximal value for brightness (read-only) */
+
+ /**
+ * @max_brightness: The maximum brightness value.
+ *
+ * This value must be set in the backlight_properties passed to
+ * devm_backlight_device_register() and shall not be modified by the
+ * driver after registration.
+ */
int max_brightness;
- /* Current FB Power mode (0: full on, 1..3: power saving
- modes; 4: full off), see FB_BLANK_XXX */
+
+ /**
+ * @power: The current power mode.
+ *
+ * User space can configure the power mode using the sysfs
+ * attribute: /sys/class/backlight/<backlight>/bl_power
+ * When the power property is updated update_status() is called.
+ *
+ * The possible values are: (0: full on, 1 to 3: power saving
+ * modes; 4: full off), see FB_BLANK_XXX.
+ *
+ * When the backlight device is enabled @power is set
+ * to FB_BLANK_UNBLANK. When the backlight device is disabled
+ * @power is set to FB_BLANK_POWERDOWN.
+ */
int power;
- /* FB Blanking active? (values as for power) */
- /* Due to be removed, please use (state & BL_CORE_FBBLANK) */
+
+ /**
+ * @fb_blank: The power state from the FBIOBLANK ioclt.
+ *
+ * When the FBIOBLANK ioctl is called @fb_blank is set to the
+ * blank parameter and the update_status() operation is called.
+ *
+ * When the backlight device is enabled @fb_blank is set
+ * to FB_BLANK_UNBLANK. When the backlight device is disabled
+ * @fb_blank is set to FB_BLANK_POWERDOWN.
+ *
+ * Backlight drivers should avoid using this property. It has been
+ * replaced by state & BL_CORE_FBLANK (although most drivers should
+ * use backlight_is_blank() as the preferred means to get the blank
+ * state).
+ *
+ * fb_blank is deprecated and will be removed.
+ */
int fb_blank;
- /* Backlight type */
+
+ /**
+ * @type: The type of backlight supported.
+ *
+ * The backlight type allows userspace to make appropriate
+ * policy desicions based on the backlight type.
+ *
+ * This value must be set in the backlight_properties
+ * passed to devm_backlight_device_register().
+ */
enum backlight_type type;
- /* Flags used to signal drivers of state changes */
+
+ /**
+ * @state: The state of the backlight core.
+ *
+ * The state is a bitmask. BL_CORE_FBBLANK is set when the display
+ * is expected to be blank. BL_CORE_SUSPENDED is set when the
+ * driver is suspended.
+ *
+ * backlight drivers are excpected to use backlight_is_blank()
+ * in their update_status() operation rather than reading the
+ * state property.
+ *
+ * The state is maintained by the core and drivers may not modify it.
+ */
unsigned int state;
- /* Type of the brightness scale (linear, non-linear, ...) */
- enum backlight_scale scale;

#define BL_CORE_SUSPENDED (1 << 0) /* backlight is suspended */
#define BL_CORE_FBBLANK (1 << 1) /* backlight is under an fb blank event */

+ /**
+ * @scale: The type of the brightness scale.
+ */
+ enum backlight_scale scale;
};

struct backlight_device {
--
2.25.1