[PATCH xserver] xfree86: Fix fallback driver sort order for Xorg -configure (v2)

[Adam Jackson]

On Tue, 2016-07-12 at 13:53 -0700, Keith Packard wrote:
> Adam Jackson <ajax at redhat.com> writes:
> 
> > The intent here was that fallback drivers would be at the end of the
> > list in order, but if a fallback driver happened to be at the end of the
> > list already that's not what would happen. Rather than open-code
> > something smarter, just use qsort.
> > 
> > Note that qsort puts things in ascending order, so somewhat backwardsly
> > fallbacks are greater than native drivers, and vesa is greater than
> > modesetting.
> > 
> > v2: Use strcmp to compare non-fallback drivers so we get a predictable
> > result if your libc's qsort isn't stable (Keith Packard)
> 
> Sorry, I wasn't clear at all. I'm assuming that the original driver list
> is relevant, and that what we want to do is pull the 'fallback' drivers
> out of the list and stick them at the end (in a sorted order). If that
> isn't right, then this patch looks great. If it is true, then we should
> figure out some way of preserving the order?

The original list is just whatever readdir() gave us, filtered to match
*_drv.so (although doing that bit with regex instead of glob because
why not). Which is how I found the bug in the first place: if you
reinstall vesa on a filesystem that gives you results in ctime order
vesa would be last in the list already, and the first swap would move
vesa to wherever fbdev/modesetting happened to be.

- ajax