framebuffer驱动全篇（二）－－－补

framebuffer驱动全篇（二）－－－补

2008-12-31 21:23

/*不可修改的屏幕信息，用户空间可见*/ struct fb_fix_screeninfo { char id[16]; /* identification string eg "TT Builtin" */ unsigned long smem_start; /* Start of frame buffer mem 显存的起始地址*/ /* (physical address) */ __u32 smem_len; /* Length of frame buffer mem 显存的大小 */ __u32 type; /* see FB_TYPE_* */ __u32 type_aux; /* Interleave for interleaved Planes */ __u32 visual; /* see FB_VISUAL_* */ __u16 xpanstep; /* zero if no hardware panning */ __u16 ypanstep; /* zero if no hardware panning */ __u16 ywrapstep; /* zero if no hardware ywrap */ __u32 line_length; /* length of a line in bytes 每行的字节数 */ unsigned long mmio_start; /* Start of Memory Mapped I/O */ /* (physical address) */ __u32 mmio_len; /* Length of Memory Mapped I/O */ __u32 accel; /* Type of acceleration available */ __u16 reserved[3]; /* Reserved for future compatibility */ }; /* Interpretation of offset for color fields: All offsets are from the right, * inside a "pixel" value, which is exactly 'bits_per_pixel' wide (means: you * can use the offset as right argument to <<). A pixel afterwards is a bit * stream and is written to video memory as that unmodified. This implies * big-endian byte order if bits_per_pixel is greater than 8. */ /*像素所占字节内，各个颜色的位分配比如RGB=888,565,555等等，*/ struct fb_bitfield { __u32 offset; /* beginning of bitfield */ __u32 length; /* length of bitfield */ __u32 msb_right; /* != 0 : Most significant bit is */ /* right */ }; /*下面的宏也不常用*/ #define FB_NONSTD_HAM 1 /* Hold-And-Modify (HAM) */ #define FB_ACTIVATE_NOW 0 /* set values immediately (or vbl)*/ #define FB_ACTIVATE_NXTOPEN 1 /* activate on next open */ #define FB_ACTIVATE_TEST 2 /* don't set, round up impossible */ #define FB_ACTIVATE_MASK 15 /* values */ #define FB_ACTIVATE_VBL 16 /* activate values on next vbl */ #define FB_CHANGE_CMAP_VBL 32 /* change colormap on vbl */ #define FB_ACTIVATE_ALL 64 /* change all VCs on this fb */ #define FB_ACCELF_TEXT 1 /* text mode acceleration */ #define FB_SYNC_HOR_HIGH_ACT 1 /* horizontal sync high active */ #define FB_SYNC_VERT_HIGH_ACT 2 /* vertical sync high active */ #define FB_SYNC_EXT 4 /* external sync */ #define FB_SYNC_COMP_HIGH_ACT 8 /* composite sync high active */ #define FB_SYNC_BROADCAST 16 /* broadcast video timings 　 Framebuffer驱动程序模型 下图会向你展示目前的framebuffer设备驱动的结构，最常用的是非标准驱动。很明显他所处的层次最高，程序编写是最容易的。 理解了这个图的，你已经很轻松的去完成一个fb驱动，比如给sa1100,s2410,s2440系列的ARM的LCD控制器写驱动。