Framebuffer programming 1 (data structure)

The most important and frequently used data structures in framebuffer programming are as follows:

Struct fb_bitfield;

Struct fb_fix_screeninfo;

Struct fb_var_screeninfo;

In the friendly source code, there are other data structures such:

Struct fb_cmap;

Struct fb_con2fbmap;

Struct fb_vblank;

Struct fb_copyarea;

Struct fb_image;

Struct fbcurpos;

Struct fb_cursor;

If you use these basic data structures, go to the source code to find the content in the header file of FB. H on the platform.

Now we will focus on the following important data structures:

Struct fb_fix_screeninfo {
Char ID [16];/* identification string eg "TT builtin "*/
Unsigned long smem_start;/* Start of Frame Buffer mem */
/* (Physical address )*/
_ U32 smem_len;/* length of Frame Buffer mem */
_ U32 type;/* See fb_type _**/
_ U32 type_aux;/* interleave for interleaved planes */
_ U32 visual;/* See fb_visual _**/
_ 2010xpanstep;/* zero if no hardware panning */
_ 2010ypanstep;/* zero if no hardware panning */
_ 2010ywrapstep;/* zero if no hardware ywrap */
_ U32 line_length;/* length of a line in bytes */
Unsigned long mmio_start;/* Start of memory mapped I/O */
/* (Physical address )*/
_ U32 mmio_len;/* length of memory mapped I/O */
_ U32 accel;/* Indicate to driver which */
/* Specific chip/card we have */
_ 2010reserved [3];/* reserved for future compatibility */
};

Struct fb_var_screeninfo {
_ U32 xres;/* visible resolution */
_ U32 yres;
_ U32 xres_virtual;/* virtual resolution */
_ U32 yres_virtual;
_ U32 xoffset;/* offset from virtual to visible */
_ U32 yoffset;/* Resolution */

_ U32 bits_per_pixel;/* Guess what */
_ U32 grayscale ;/*! = 0 graylevels instead of colors */

Struct fb_bitfield red;/* bitfield in FB MEm if true color ,*/
Struct fb_bitfield green;/* else only length is significant */
Struct fb_bitfield blue;
Struct fb_bitfield Transp;/* Transparency */

_ U32 nonstd ;/*! = 0 non standard pixel format */

_ U32 activate;/* See fb_activate _**/

_ U32 height;/* Height of picture in mm */
_ U32 width;/* width of picture in mm */

_ U32 accel_flags;/* (obsolete) See fb_info.flags */

/* Timing: All values in pixclocks, blocks t pixclock (of course )*/
_ U32 pixclock;/* pixel clock in PS (Pico seconds )*/
_ U32 left_margin;/* time from sync to picture */
_ U32 right_margin;/* time from picture to sync */
_ U32 upper_margin;/* time from sync to picture */
_ U32 lower_margin;
_ U32 hsync_len;/* length of horizontal sync */
_ U32 vsync_len;/* length of vertical sync */
_ U32 sync;/* See fb_sync _**/
_ U32 vmode;/* See fb_vmode _**/
_ U32 rotate;/* angle we rotate counter clockwise */
_ U32 reserved [5];/* reserved for future compatibility */
};

Struct fb_bitfield {
_ U32 offset;/* beginning of bitfield */
_ U32 length;/* length of bitfield */
_ U32 msb_right ;/*! = 0: most significant bit is */
/* Right */
};