结合APP分析LCD驱动程序#
结合APP分析LCD驱动程序#
本节视频对应源码在GIT仓库中，位置如下(这2个文件是完全一样的)：
doc_and_source_for_drivers\STM32MP157\source\A7\03_LCD\04_fb_test
或：
doc_and_source_for_drivers\IMX6ULL\source\03_LCD\04_fb_test
1. open#
app: open("/dev/fb0", ...) 主设备号: 29, 次设备号: 0
--------------------------------------------------------------
kernel:
fb_open // fbmem.c
struct fb_info *info;
info = get_fb_info(fbidx);
if (info->fbops->fb_open) {
res = info->fbops->fb_open(info,1); // 硬件相关的驱动
if (res)
module_put(info->fbops->owner);
}
2. 获得可变信息(含有分辨率等)#
app: ioctl(fd, FBIOGET_VSCREENINFO, &fb_info->var);
-------------------------------------------------------------------------
kernel:
fb_ioctl // fbmem.c
struct fb_info *info = file_fb_info(file);
do_fb_ioctl(info, cmd, arg);
var = info->var; // 硬件相关的驱动设置的
ret = copy_to_user(argp, &var, sizeof(var)) ? -EFAULT : 0;
3. 获得固定信息(含有显存信息)#
app: ioctl(fd, FBIOGET_FSCREENINFO, &fb_info->fix);
-------------------------------------------------------------------------
kernel:
fb_ioctl // fbmem.c
struct fb_info *info = file_fb_info(file);
do_fb_ioctl(info, cmd, arg);
fix = info->fix; // 硬件相关的驱动设置的
ret = copy_to_user(argp, &fix, sizeof(fix)) ? -EFAULT : 0;
4. mmap#
app：void *ptr = mmap(0,
fb_info->var.yres_virtual * fb_info->fix.line_length,
PROT_WRITE | PROT_READ,
MAP_SHARED, fd, 0);
-------------------------------------------------------------------------
kernel:
fb_mmap // fbmem.c
struct fb_info *info = file_fb_info(file);
start = info->fix.smem_start;
len = info->fix.smem_len;
return vm_iomap_memory(vma, start, len);