如何计算Framebuffer大小 内核空间Framebuffer大小的计算： 1280*720*4 = 3.5M *2 = 7M（base+ovly） 2. 用户空间Framebuffer大小的计算： info->fix.line_length = var->xres_virtual * var->bits_per_pixel / 8 = 320 *2=640 info.yres_virtual = info.yres * NUM_BUFFERS = 480*2=960; size_t fbSize = roundUpToPageSize(finfo.line_length * info.yres_virtual)= 640*960=600K;