fbdev: add support for handoff from firmware to hw framebuffers

With KMS we have ran into an issue where we really want the KMS fb driver
to be the one running the console, so panics etc can be shown by switching
out of X etc.

However with vesafb/efifb built-in, we end up with those on fb0 and the
KMS fb driver on fb1, driving the same piece of hw, so this adds an fb
info flag to denote a firmware fbdev, and adds a new aperture base/size
range which can be compared when the hw drivers are installed to see if
there is a conflict with a firmware driver, and if there is the firmware
driver is unregistered and the hw driver takes over.

It uses new aperture_base/size members instead of comparing on the fix
smem_start/length, as smem_start/length might for example only cover the
first 1MB of the PCI aperture, and we could allocate the kms fb from 8MB
into the aperture, thus they would never overlap.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Dave Airlie <airlied@redhat.com>
Acked-by: Peter Jones <pjones@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 31 insertions, 0 deletions

diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index d412a1d..f8a09bf 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -1462,6 +1462,16 @@ static int fb_check_foreignness(struct fb_info *fi)
 	return 0;
 }
 
+static bool fb_do_apertures_overlap(struct fb_info *gen, struct fb_info *hw)
+{
+	/* is the generic aperture base the same as the HW one */
+	if (gen->aperture_base == hw->aperture_base)
+		return true;
+	/* is the generic aperture base inside the hw base->hw base+size */
+	if (gen->aperture_base > hw->aperture_base && gen->aperture_base <= hw->aperture_base + hw->aperture_size)
+		return true;
+	return false;
+}
 /**
  *	register_framebuffer - registers a frame buffer device
  *	@fb_info: frame buffer info structure
@@ -1485,6 +1495,23 @@ register_framebuffer(struct fb_info *fb_info)
 	if (fb_check_foreignness(fb_info))
 		return -ENOSYS;
 
+	/* check all firmware fbs and kick off if the base addr overlaps */
+	for (i = 0 ; i < FB_MAX; i++) {
+		if (!registered_fb[i])
+			continue;
+
+		if (registered_fb[i]->flags & FBINFO_MISC_FIRMWARE) {
+			if (fb_do_apertures_overlap(registered_fb[i], fb_info)) {
+				printk(KERN_ERR "fb: conflicting fb hw usage "
+				       "%s vs %s - removing generic driver\n",
+				       fb_info->fix.id,
+				       registered_fb[i]->fix.id);
+				unregister_framebuffer(registered_fb[i]);
+				break;
+			}
+		}
+	}
+
 	num_registered_fb++;
 	for (i = 0 ; i < FB_MAX; i++)
 		if (!registered_fb[i])
@@ -1586,6 +1613,10 @@ unregister_framebuffer(struct fb_info *fb_info)
 	device_destroy(fb_class, MKDEV(FB_MAJOR, i));
 	event.info = fb_info;
 	fb_notifier_call_chain(FB_EVENT_FB_UNREGISTERED, &event);
+
+	/* this may free fb info */
+	if (fb_info->fbops->fb_destroy)
+		fb_info->fbops->fb_destroy(fb_info);
 done:
 	return ret;
 }