drm/format-helper: Cache buffers with struct drm_format_conv_state

Hold temporary memory for format conversion in an instance of struct
drm_format_conv_state. Update internal helpers of DRM's format-conversion
code accordingly. Drivers will later be able to maintain this cache by
themselves.

Besides caching, struct drm_format_conv_state will be useful to hold
additional information for format conversion, such as palette data or
foreground/background colors. This will enable conversion from indexed
color formats to component-based formats.

v5:
	* improve documentation (Javier, Noralf)
v3:
	* rename struct drm_xfrm_buf to struct drm_format_conv_state
	  (Javier)
	* remove managed cleanup
	* add drm_format_conv_state_copy() for shadow-plane support

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Noralf Trønnes <noralf@tronnes.org>
Tested-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231009141018.11291-2-tzimmermann@suse.de

1 files changed, 51 insertions, 0 deletions

diff --git a/include/drm/drm_format_helper.h b/include/drm/drm_format_helper.h
index 291deb09475b..724a9baf7315 100644
--- a/include/drm/drm_format_helper.h
+++ b/include/drm/drm_format_helper.h
@@ -15,6 +15,57 @@ struct drm_rect;
 
 struct iosys_map;
 
+/**
+ * struct drm_format_conv_state - Stores format-conversion state
+ *
+ * DRM helpers for format conversion store temporary state in
+ * struct drm_xfrm_buf. The buffer's resources can be reused
+ * among multiple conversion operations.
+ *
+ * All fields are considered private.
+ */
+struct drm_format_conv_state {
+	struct {
+		void *mem;
+		size_t size;
+		bool preallocated;
+	} tmp;
+};
+
+#define __DRM_FORMAT_CONV_STATE_INIT(_mem, _size, _preallocated) { \
+		.tmp = { \
+			.mem = (_mem), \
+			.size = (_size), \
+			.preallocated = (_preallocated), \
+		} \
+	}
+
+/**
+ * DRM_FORMAT_CONV_STATE_INIT - Initializer for struct drm_format_conv_state
+ *
+ * Initializes an instance of struct drm_format_conv_state to default values.
+ */
+#define DRM_FORMAT_CONV_STATE_INIT \
+	__DRM_FORMAT_CONV_STATE_INIT(NULL, 0, false)
+
+/**
+ * DRM_FORMAT_CONV_STATE_INIT_PREALLOCATED - Initializer for struct drm_format_conv_state
+ * @_mem: The preallocated memory area
+ * @_size: The number of bytes in _mem
+ *
+ * Initializes an instance of struct drm_format_conv_state to preallocated
+ * storage. The caller is responsible for releasing the provided memory range.
+ */
+#define DRM_FORMAT_CONV_STATE_INIT_PREALLOCATED(_mem, _size) \
+	__DRM_FORMAT_CONV_STATE_INIT(_mem, _size, true)
+
+void drm_format_conv_state_init(struct drm_format_conv_state *state);
+void drm_format_conv_state_copy(struct drm_format_conv_state *state,
+				const struct drm_format_conv_state *old_state);
+void *drm_format_conv_state_reserve(struct drm_format_conv_state *state,
+				    size_t new_size, gfp_t flags);
+void drm_format_conv_state_release(struct drm_format_conv_state *state);
+
 unsigned int drm_fb_clip_offset(unsigned int pitch, const struct drm_format_info *format,
 				const struct drm_rect *clip);