[Linux-fbdev-devel] Explanations about fb_ops and fbgen_hwswitch

[<chr...@ph...>]

Hello,

I have to write a fb (!?) on embedded system. I will certainly reuse the sa1100fb.c frame buffer.

Can someone explain the difference between the following examples :

In some framebuffer drivers there is :
either:
************************* Ex 1
(from sa1100fb.c)
static struct fb_ops sa1100fb_ops = {
     owner:         THIS_MODULE,
     fb_get_fix:    sa1100fb_get_fix,
     fb_get_var:    sa1100fb_get_var,
     fb_set_var:    sa1100fb_set_var,
     fb_get_cmap:   sa1100fb_get_cmap,
     fb_set_cmap:   sa1100fb_set_cmap,
};

with sa1100fb_encode_fix(),  sa1100fb_getcolreg(),  sa1100fb_setcolreg() etc, defined which could belong to the fbgen_hwswitch struct.

or:
************************* Ex 2
(from pm2fb.c)
static struct fbgen_hwswitch pm2fb_hwswitch={
     pm2fb_detect, pm2fb_encode_fix, pm2fb_decode_var,
     pm2fb_encode_var, pm2fb_get_par, pm2fb_set_par,
     pm2fb_getcolreg, pm2fb_setcolreg, pm2fb_pan_display,
     pm2fb_blank, pm2fb_set_disp
};

static struct fb_ops pm2fb_ops={
     owner:         THIS_MODULE,
     fb_get_fix:    fbgen_get_fix,
     fb_get_var:    fbgen_get_var,
     fb_set_var:    fbgen_set_var,
     fb_get_cmap:   fbgen_get_cmap,
     fb_set_cmap:   fbgen_set_cmap,
     fb_pan_display:     fbgen_pan_display,
};
___________________________________________________
So in Ex1 why not defining the sa1100fb_hwswitch variable ???

Or when do you define xxxxfb_hwswitch variable and put fbgen_xxx functions in xxxxfb_ops var (like ex2) rather  than writing function for only xxxxfb_ops (like ex 1)  ?

ThanX

Christophe Levantis