[PATCH v2 06/16] backlight: improve backlight_device documentation

[Daniel Thompson]

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 at ravnborg.org>
> Cc: Lee Jones <lee.jones at linaro.org>
> Cc: Daniel Thompson <daniel.thompson at linaro.org>
> Cc: Jingoo Han <jingoohan1 at gmail.com>
> ---
>  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
>