some divide by zero bugs in >fb_check_var() functions

My static checker find a number of divide by zero bugs in
->fb_check_var() functions.  The call tree looks like this:

  do_fb_ioctl() <- get var from the user.
  -> fb_set_var()
     -> info->fbops->fb_check_var(var, info); <- divide by zero bugs

I wonder if we could add some checking in fb_set_var() to prevent this.

drivers/video/asiliantfb.c:230 asiliantfb_check_var() error: potential divide by zero bug '/ var->pixclock'.
drivers/video/asiliantfb.c:231 asiliantfb_check_var() error: potential divide by zero bug '/ var->pixclock'.
drivers/video/asiliantfb.c:232 asiliantfb_check_var() error: potential divide by zero bug '/ var->pixclock'.
drivers/video/cirrusfb.c:535 cirrusfb_check_var() error: potential divide by zero bug '/ var->bits_per_pixel'.
drivers/video/cirrusfb.c:581 cirrusfb_check_var() error: potential divide by zero bug '/ var->xres_virtual'.
drivers/video/cyber2000fb.c:843 cyber2000fb_check_var() error: potential divide by zero bug '/ (var->bits_per_pixel * var->xres_virtual)'.
drivers/video/imsttfb.c:843 imsttfb_check_var() error: potential divide by zero bug '/ var->xres_virtual'.
drivers/video/neofb.c:594 neofb_check_var() error: potential divide by zero bug '/ (var->pixclock)'.
drivers/video/neofb.c:702 neofb_check_var() error: potential divide by zero bug '/ (var->xres_virtual * var->bits_per_pixel)'.
drivers/video/pm2fb.c:624 pm2fb_check_var() error: potential divide by zero bug '/ (var->pixclock)'.
drivers/video/pm3fb.c:1007 pm3fb_check_var() error: potential divide by zero bug '/ (var->pixclock)'.
drivers/video/s3fb.c:601 s3fb_check_var() error: potential divide by zero bug '/ (var->pixclock)'.
drivers/video/savage/savagefb_driver.c:952 savagefb_check_var() error: potential divide by zero bug '/ (var->xres_virtual * var->bits_per_pixel)'.
drivers/video/sstfb.c:359 sstfb_check_var() error: potential divide by zero bug '/ (var->pixclock)'.
drivers/video/sstfb.c:361 sstfb_check_var() error: potential divide by zero bug '/ (var->pixclock)'.
drivers/video/tdfxfb.c:518 tdfxfb_check_var() error: potential divide by zero bug '/ (var->pixclock)'.
drivers/video/tdfxfb.c:519 tdfxfb_check_var() error: potential divide by zero bug '/ (var->pixclock)'.
drivers/video/tridentfb.c:918 tridentfb_check_var() error: potential divide by zero bug '/ line_length'.
drivers/video/tridentfb.c:973 tridentfb_check_var() error: potential divide by zero bug '/ (var->pixclock)'.

regards,
dan carpenter