On Wed, Apr 22, 2015 at 09:54:38AM -0400, Doug Ledford wrote: > On Tue, 2015-04-21 at 14:50 -0700, Luis R. Rodriguez wrote: > > This: > > + /* MTRR was used if this is non-zero */ > > + if (!dd->wc_cookie) > > vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot); > > And this: > > + dd->wc_cookie = arch_phys_wc_add(pioaddr, piolen); > > + if (dd->wc_cookie < 0) > > + ret = -EINVAL; > > don't agree on what wc_cookie will be on error. Can you elaborate? The one below is the one that starts things, and arch_phys_wc_add() will return 0 on PAT systems. For non-PAT systems it will return a number > 0 *iff* a valid MTRR was added. It will return negative onloy on error then. The change above is meant to replace a check put in place to see if PAT was enabled. The way we replace this is to ensure that arch_phys_wc_add() returned 0. If you disagree it'd be great if you can elaborate why. Luis -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
