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drivers/fbdev/efifb: Allow BAR to be moved instead of claiming it
On UEFI systems, the firmware may expose a Graphics Output Protocol (GOP) instance to which the efifb driver attempts to attach in order to provide a minimal, unaccelerated framebuffer. The GOP protocol itself is not very sophisticated, and only describes the offset and size of the framebuffer in memory, and the pixel format. If the GOP framebuffer is provided by a PCI device, it will have been configured and enabled by the UEFI firmware, and the GOP protocol will simply point into a live BAR region. However, the GOP protocol itself does not describe this relation, and so we have to take care not to reconfigure the BAR without taking efifb's dependency on it into account. Commit: 55d728a4 ("efi/fb: Avoid reconfiguration of BAR that covers the framebuffer") attempted to do so by claiming the BAR resource early on, which prevents the PCI resource allocation routines from changing it. However, it turns out that this only works if the PCI device is not behind any bridges, since the bridge resources need to be claimed first. So instead, allow the BAR to be moved, but make the efifb driver deal with that gracefully. So record the resource that covers the BAR early on, and if it turns out to have moved by the time we probe the efifb driver, update the framebuffer address accordingly. While this is less likely to occur on x86, given that the firmware's PCI resource allocation is more likely to be preserved, this is a worthwhile sanity check to have in place, and so let's remove the preprocessor conditional that makes it !X86 only. Signed-off-by:Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: