drivers: display: Change display buffer pitch from pixel to byte

The `pitch` in `struct display_buffer_descriptor` is defined as
"Number of pixels between consecutive rows in the data buffer".

Limitation:
Some display controller needs the pitch of byte be dividable
by an even value (e.g., 4, 64, ...), if the parameter pitch here
is the number of pixels, then the RGB888 (3 bytes per pixel) can't work

Change the unit of `pitch` from pixel to byte

Signed-off-by: Jason Yu <zejiang.yu@nxp.com>

Author: zejiang0jason

include/zephyr/drivers/display.h

@@ -143,15 +143,46 @@ struct display_capabilities {
 	enum display_orientation current_orientation;
 };
 
-/** @brief Structure to describe display data buffer layout */
+/**
+ * @brief Structure to describe display data buffer layout
+ *
+ * @verbatim
+ *  Frame Buffer Memory Layout:
+ *
+ *   <----------------- pitch (bytes per row) ------------------>
+ *   <------ width * bytes_per_pixel ------>
+ *  +---------------------------------------+--------------------+
+ *  | Pixel | Pixel | Pixel | ... | Pixel   |   Padding/Unused   |  ^
+ *  | (0,0) | (1,0) | (2,0) |     |(w-1,0)  |                    |  |
+ *  +---------------------------------------+--------------------+  |
+ *  | Pixel | Pixel | Pixel | ... | Pixel   |   Padding/Unused   |  |
+ *  | (0,1) | (1,1) | (2,1) |     |(w-1,1)  |                    | height
+ *  +---------------------------------------+--------------------+ (rows)
+ *  | Pixel | Pixel | Pixel | ... | Pixel   |   Padding/Unused   |  |
+ *  | (0,2) | (1,2) | (2,2) |     |(w-1,2)  |                    |  |
+ *  +---------------------------------------+--------------------+  |
+ *  |  ...  |  ...  |  ...  | ... |  ...    |        ...         |  |
+ *  +---------------------------------------+--------------------+  |
+ *  | Pixel | Pixel | Pixel | ... | Pixel   |   Padding/Unused   |  |
+ *  |(0,h-1)|(1,h-1)|(2,h-1)|     |(w-1,h-1)|                    |  v
+ *  +---------------------------------------+---------------------+
+ *
+ *  width  = Number of pixels per row (visible width)
+ *  height = Number of rows (visible height)
+ *  pitch  = Number of bytes per row (including padding for alignment)
+ *
+ *  Note: pitch >= width * bytes_per_pixel
+ *        The difference is padding added for memory alignment requirements.
+ * @endverbatim
+ */
 struct display_buffer_descriptor {
 	/** Data buffer size in bytes */
 	uint32_t buf_size;
 	/** Data buffer row width in pixels */
 	uint16_t width;
 	/** Data buffer column height in pixels */
 	uint16_t height;
-	/** Number of pixels between consecutive rows in the data buffer */
+	/** Number of bytes between consecutive rows in the data buffer */
 	uint16_t pitch;
 	/** Indicates that this is not the last write buffer of the frame */
 	bool frame_incomplete;

include/zephyr/drivers/mipi_dbi.h

@@ -258,7 +258,8 @@ static inline int mipi_dbi_command_read(const struct device *dev,
  * @param config MIPI DBI configuration
  * @param framebuf: framebuffer to write to display
  * @param desc: descriptor of framebuffer to write. Note that the pitch must
- *   be equal to width. "buf_size" field determines how many bytes will be
+ *   be equal to width * bytes_per_pixel (pitch is now in bytes per row).
+ *   "buf_size" field determines how many bytes will be
  *   written.
  * @param pixfmt: pixel format of framebuffer data
  * @retval 0 buffer write succeeded.