Linux Framebuffer modes

Question

I am currently working on embedded linux framebuffers. I know how to display the available resolutions of my system by typing:

cat /sys/class/graphics/fb0/modes

This gives me a list of resolutions, for instance:

U:720x576p-50
D:1920x1080p-50
D:1280x720p-50
D:1920x1080i-60
D:1920x1080i-50
U:1440x900p-60
S:1280x1024p-60
V:1024x768p-60
V:800x600p-60
V:640x480p-60
D:1280x720p-60
D:1920x1080p-60

I would like to know what does the first character of each lines mean (S, U, V or D). Is there a standard/documentation listing all the possible characters?

Answer 1

From the linux kernel source function mode_string()

char m = 'U';
if (mode->flag & FB_MODE_IS_DETAILED)
        m = 'D';
if (mode->flag & FB_MODE_IS_VESA)
        m = 'V';
if (mode->flag & FB_MODE_IS_STANDARD)
        m = 'S';

so it's U unknown, D detailed, V vesa, S standard.