Commit 3012248f authored by Simon Ser's avatar Simon Ser
Browse files

drm: document drm_property_enum.value for bitfields 



When a property has the type DRM_MODE_PROP_BITMASK, the value field
stores a bitshift, not a bitmask, which can be surprising.

Signed-off-by: default avatarSimon Ser <contact@emersion.fr>
Cc: Leandro Ribeiro <leandro.ribeiro@collabora.com>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: default avatarPekka Paalanen <pekka.paalanen@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/NUZTPTKKZtAlDhxIXFB1qrUqWBYKapkBxCnb1S1bc3g@cp3-web-033.plabs.ch
parent 03b7c552

include/drm/drm_property.h

+8 −1
Original line number Diff line number Diff line
@@ -31,7 +31,6 @@ 


/**

 * struct drm_property_enum - symbolic values for enumerations

 * @value: numeric property value for this enum entry

 * @head: list of enum values, linked to &drm_property.enum_list

 * @name: symbolic name for the enum

 *
@@ -39,6 +38,14 @@ 
 * decoding for each value. This is used for example for the rotation property.

 */

struct drm_property_enum {

	/**

	 * @value: numeric property value for this enum entry

	 *

	 * If the property has the type &DRM_MODE_PROP_BITMASK, @value stores a

	 * bitshift, not a bitmask. In other words, the enum entry is enabled

	 * if the bit number @value is set in the property's value. This enum

	 * entry has the bitmask ``1 << value``.

	 */

	uint64_t value;

	struct list_head head;

	char name[DRM_PROP_NAME_LEN];