docs(disp): describe how to swap the bytes with RGB565 format

docs/porting/disp.rst

@@ -136,6 +136,7 @@ or anything else to optimize while the waiting for flush.
 If ``flush_wait_cb`` is not set, LVGL assume that `lv_display_flush_ready`
 is used.
 
+
 Rotation
 --------
 
@@ -170,6 +171,29 @@ used as a well.
 It's very important that draw buffer(s) should be large enough for any
 selected color format.
 
+
+Swap endianness
+--------------
+
+In case of RGB565 color format it might be required to swap the 2 bytes
+because the SPI, I2C or 8 bit parallel port periphery sends them in the wrong order.
+
+The ideal solution is configure the hardware to handle the 16 bit data with different byte order,
+however if it's not possible `:cpp:expr:`lv_draw_sw_rgb565_swap(buf, buf_size_in_px)`
+can be called in the ``flush_cb`` to swap the bytes.
+
+If you wish you can also write your own function, or use assembly instructions for
+the fastest possible byte swapping.
+
+Note that this is not about swapping the Red and Blue channel but converting
+
+``RRRRR GGG | GGG BBBBB``
+
+to
+
+``GGG BBBBB | RRRRR GGG``.
+
+
 User data
 ---------
 

src/display/lv_display.h

@@ -259,12 +259,14 @@ void lv_display_set_flush_wait_cb(lv_display_t * disp, lv_display_flush_wait_cb_
 
 /**
  * Set the color format of the display.
- * If set to other than `LV_COLOR_FORMAT_NATIVE` the layer's `buffer_convert` function will be used
- * to convert the rendered content to the desired color format.
  * @param disp              pointer to a display
- * @param color_format      By default `LV_COLOR_FORMAT_NATIVE` to render with L8, RGB565, RGB888 or ARGB8888.
- *                          `LV_COLOR_FORMAT_NATIVE_REVERSE` to change endianness.
- *
+ * @param color_format      Possible values are
+ *                          - LV_COLOR_FORMAT_RGB565
+ *                          - LV_COLOR_FORMAT_RGB888
+ *                          - LV_COLOR_FORMAT_XRGB888
+ *                          - LV_COLOR_FORMAT_ARGB888
+ *@note To change the endianness of the rendered image in case of RGB565 format
+ *      (i.e. swap the 2 bytes) call `lv_draw_sw_rgb565_swap` in the flush_cb
  */
 void lv_display_set_color_format(lv_display_t * disp, lv_color_format_t color_format);