515_33.diff

From 32017a4771c8a1fe0b27f59644b105b033cff5c8 Mon Sep 17 00:00:00 2001
From: Daniel Kolesa <daniel@octaforge.org>
Date: Mon, 11 Apr 2022 00:05:30 +0200
Subject: [PATCH] REVERT: fbdev: Hot-unplug firmware fb devices on forced
 removal

This breaks at very least virtio-gpu, resulting on NULL dereference
upon probe.

https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/drivers/video/fbdev/core?h=linux-5.15.y&id=c894ac44786cfed383a6c6b20c1bfb12eb96018a
---
 drivers/video/fbdev/core/fbmem.c | 29 +++--------------------------
 1 file changed, 3 insertions(+), 26 deletions(-)

diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
index 91145d9..7bd5e2a 100644
--- a/drivers/video/fbdev/core/fbmem.c
+++ b/drivers/video/fbdev/core/fbmem.c
@@ -25,7 +25,6 @@
 #include <linux/init.h>
 #include <linux/linux_logo.h>
 #include <linux/proc_fs.h>
-#include <linux/platform_device.h>
 #include <linux/seq_file.h>
 #include <linux/console.h>
 #include <linux/kmod.h>
@@ -1558,36 +1557,18 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a,
 	/* check all firmware fbs and kick off if the base addr overlaps */
 	for_each_registered_fb(i) {
 		struct apertures_struct *gen_aper;
-		struct device *device;
 
 		if (!(registered_fb[i]->flags & FBINFO_MISC_FIRMWARE))
 			continue;
 
 		gen_aper = registered_fb[i]->apertures;
-		device = registered_fb[i]->device;
 		if (fb_do_apertures_overlap(gen_aper, a) ||
 			(primary && gen_aper && gen_aper->count &&
 			 gen_aper->ranges[0].base == VGA_FB_PHYS)) {
 
 			printk(KERN_INFO "fb%d: switching to %s from %s\n",
 			       i, name, registered_fb[i]->fix.id);
-
-			/*
-			 * If we kick-out a firmware driver, we also want to remove
-			 * the underlying platform device, such as simple-framebuffer,
-			 * VESA, EFI, etc. A native driver will then be able to
-			 * allocate the memory range.
-			 *
-			 * If it's not a platform device, at least print a warning. A
-			 * fix would add code to remove the device from the system.
-			 */
-			if (dev_is_platform(device)) {
-				registered_fb[i]->forced_out = true;
-				platform_device_unregister(to_platform_device(device));
-			} else {
-				pr_warn("fb%d: cannot remove device\n", i);
-				do_unregister_framebuffer(registered_fb[i]);
-			}
+			do_unregister_framebuffer(registered_fb[i]);
 		}
 	}
 }
@@ -1914,13 +1895,9 @@ EXPORT_SYMBOL(register_framebuffer);
 void
 unregister_framebuffer(struct fb_info *fb_info)
 {
-	bool forced_out = fb_info->forced_out;
-
-	if (!forced_out)
-		mutex_lock(&registration_lock);
+	mutex_lock(&registration_lock);
 	do_unregister_framebuffer(fb_info);
-	if (!forced_out)
-		mutex_unlock(&registration_lock);
+	mutex_unlock(&registration_lock);
 }
 EXPORT_SYMBOL(unregister_framebuffer);
 
-- 
2.35.1