Freescale Semiconductor i.MX 6SoloLite Linux, Справочное руководство

Страница: 63 / 199

6.3.6 Grayscale Framebuffer Selection
The SPDC framebuffer driver supports the use of 4-bit grayscale (Y4) and 4-bit inverted
grayscale (Y4 inverted) pixel formats for the framebuffer (in addition to the more
common RGB565 pixel format). In order to configure the framebuffer format as 4-bit
grayscale, the application would call the FBIOPUT_VSCREENINFO framebuffer ioctl.
This ioctl takes an fb_var_screeninfo pointer as a parameter. This parameter specifies the
attributes of the framebuffer and allows the application to request changes to the
framebuffer format. There are two key members of the fb_var_screeninfo parameter that
must be set in order to request a change to 4-bit grayscale format: bits_per_pixel and
grayscale. bits_per_pixel must be set to 4, and grayscale must be set to one of the 2 valid
grayscale format values: GRAYSCALE_4BIT or GRAYSCALE_4BIT_INVERTED.
The following code snippet demonstrates a request to change the framebuffer to use the
Y4 pixel format:
fb_screen_info screen_info;
screen_info.bits_per_pixel = 4;
screen_info.grayscale = GRAYSCALE_4BIT;
retval = ioctl(fd_fb0, FBIOPUT_VSCREENINFO, &screen_info);
6.4 Source Code Structure
Table below lists the source files associated with the SPDC driver. These files are
available in the following directory:
drivers/video/mxc
Table 6-1. SPDC Driver Files
File Description
mxc_spdc_fb.c The SPDC frame buffer driver.
mxc_spdc_fb.h Register definitions for the SPDC module.
Table below lists the global header files associated with the SPDC driver. These files are
available in the following directory:
include/linux/
Table 6-2. SPDC Global Header Files
File Description
mxcfb.h Header file for the MXC framebuffer drivers
mxcfb_epdc_kernel.h Header file for direct kernel access to the SPDC API extension
Chapter 6 Sipix Display Controller (SPDC) Frame Buffer Driver
i.MX 6SoloLite Linux Reference Manual, Rev. L3.0.35_4.1.0, 09/2013
Freescale Semiconductor, Inc. 63