On Sun, May 17, 2020 at 09:01:29PM +0200, Sam Ravnborg wrote:
> Improve the documentation for backlight_device and
> adapt it to kernel-doc style.
>
> Signed-off-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
> Cc: Lee Jones <lee.jones@xxxxxxxxxx>
> Cc: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
> Cc: Jingoo Han <jingoohan1@xxxxxxxxx>
> ---
> include/linux/backlight.h | 81 ++++++++++++++++++++++++++++-----------
> 1 file changed, 58 insertions(+), 23 deletions(-)
>
> diff --git a/include/linux/backlight.h b/include/linux/backlight.h
> index 7f9cef299d6e..e2d72936bf05 100644
> --- a/include/linux/backlight.h
> +++ b/include/linux/backlight.h
> @@ -14,21 +14,6 @@
> #include <linux/mutex.h>
> #include <linux/notifier.h>
>
> -/* Notes on locking:
> - *
> - * backlight_device->ops_lock is an internal backlight lock protecting the
> - * ops pointer and no code outside the core should need to touch it.
> - *
> - * Access to update_status() is serialised by the update_lock mutex since
> - * most drivers seem to need this and historically get it wrong.
> - *
> - * Most drivers don't need locking on their get_brightness() method.
> - * If yours does, you need to implement it in the driver. You can use the
> - * update_lock mutex if appropriate.
> - *
> - * Any other use of the locks below is probably wrong.
> - */
> -
> enum backlight_update_reason {
> BACKLIGHT_UPDATE_HOTKEY,
> BACKLIGHT_UPDATE_SYSFS,
> @@ -221,30 +206,80 @@ struct backlight_properties {
> enum backlight_scale scale;
> };
>
> +/**
> + * struct backlight_device - backlight device data
> + *
> + * This structure holds all data required by a backlight device.
> + */
> struct backlight_device {
> - /* Backlight properties */
> + /**
> + * @props:
> + *
As last patch. Why no brief descriptions?
> + * Backlight properties
> + */
> struct backlight_properties props;
>
> - /* Serialise access to update_status method */
> + /**
> + * @update_lock:
> + *
> + * update_lock is an internal backlight lock that serialise access
> + * to the update_status() method. The iupdate_lock mutex shall not be used
> + * by backlight drivers.
In addition to the typo this directly contradicts the advice in the
original "Notes on locking".
A change this dramatic needs to be fully explaining in the patch
description.
Daniel.
> + */
> struct mutex update_lock;
>
> - /* This protects the 'ops' field. If 'ops' is NULL, the driver that
> - registered this device has been unloaded, and if class_get_devdata()
> - points to something in the body of that driver, it is also invalid. */
> + /**
> + * @ops_lock:
> + *
> + * ops_lock is an internal backlight lock that protects the ops pointer
> + * and is used around all accesses to ops and when the operations are
> + * invoked. The mutex shall not be used by backlight drivers.
> + */
> struct mutex ops_lock;
> +
> + /**
> + * @ops:
> + *
> + * Pointer to the backlight operations. If ops is NULL, the driver that
> + * registered this device has been unloaded, and if class_get_devdata()
> + * points to something in the body of that driver, it is also invalid.
> + */
> const struct backlight_ops *ops;
>
> - /* The framebuffer notifier block */
> + /**
> + * @fb_notif:
> + *
> + * The framebuffer notifier block
> + */
> struct notifier_block fb_notif;
>
> - /* list entry of all registered backlight devices */
> + /**
> + * @entry:
> + *
> + * List entry of all registered backlight devices
> + */
> struct list_head entry;
>
> + /**
> + * @dev:
> + *
> + * Parent device.
> + */
> struct device dev;
>
> - /* Multiple framebuffers may share one backlight device */
> + /**
> + * @fb_bl_on:
> + *
> + * Multiple fbdev's may share one backlight device. The fb_bl_on
> + * records the state of the individual fbdev.
> + */
> bool fb_bl_on[FB_MAX];
>
> + /**
> + * @use_count:
> + *
> + * The number of uses of fb_bl_on.
> + */
> int use_count;
> };
>
> --
> 2.25.1
>
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