Use of 'reserved' fields in var_screeninfo
From: Kevin Hilman <hidden>
Date: 2005-11-14 19:17:37
Hello,
I've got a question about the purpose of the reserved fields in the
var_screeninfo struct:
struct fb_var_screeninfo {
[ ... ]
__u32 reserved[5]; /* Reserved for future compatibility */
};
What are these reserved for? Is it appropriate for drivers to use these for
additional, HW-specific values that are then made available to the VSCREENINFO
ioctls?
If a driver does store state here, or attempt to pass info using an ioctl, the
data is promptly overwritten by fbcon during an fbcon_switch(), when it creates
a var_screeninfo struct, memsets it to zero, copies a couple fields and passes
it to fb_set_var().
I have a patch to copy the 'reserved' fields during an fbcon_switch() that
solves the problem but I'm not sure if this is the right thing to do.
--
Kevin Hilman
MontaVista Software -- http://www.mvista.com/
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