hyperv: avoid dependency on screen_info

The two hyperv framebuffer drivers (hyperv_fb or hyperv_drm_drv) access the
global screen_info in order to take over from the sysfb framebuffer, which
in turn could be handled by simplefb, simpledrm or efifb. Similarly, the
vmbus_drv code marks the original EFI framebuffer as reserved, but this
is not required if there is no sysfb.

As a preparation for making screen_info itself more local to the sysfb
helper code, add a compile-time conditional in all three files that relate
to hyperv fb and just skip this code if there is no sysfb that needs to
be unregistered.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20231009211845.3136536-9-arnd@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: arndb

drivers/gpu/drm/hyperv/hyperv_drm_drv.c

@@ -73,9 +73,10 @@ static int hyperv_setup_vram(struct hyperv_drm_device *hv,
 	struct drm_device *dev = &hv->dev;
 	int ret;
 
-	drm_aperture_remove_conflicting_framebuffers(screen_info.lfb_base,
-						     screen_info.lfb_size,
-						     &hyperv_driver);
+	if (IS_ENABLED(CONFIG_SYSFB))
+		drm_aperture_remove_conflicting_framebuffers(screen_info.lfb_base,
+							     screen_info.lfb_size,
+							     &hyperv_driver);
 
 	hv->fb_size = (unsigned long)hv->mmio_megabytes * 1024 * 1024;
 

drivers/hv/vmbus_drv.c

@@ -2100,8 +2100,10 @@ static void __maybe_unused vmbus_reserve_fb(void)
 
 	if (efi_enabled(EFI_BOOT)) {
 		/* Gen2 VM: get FB base from EFI framebuffer */
-		start = screen_info.lfb_base;
-		size = max_t(__u32, screen_info.lfb_size, 0x800000);
+		if (IS_ENABLED(CONFIG_SYSFB)) {
+			start = screen_info.lfb_base;
+			size = max_t(__u32, screen_info.lfb_size, 0x800000);
+		}
 	} else {
 		/* Gen1 VM: get FB base from PCI */
 		pdev = pci_get_device(PCI_VENDOR_ID_MICROSOFT,

drivers/video/fbdev/hyperv_fb.c

@@ -1030,7 +1030,7 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
 			goto getmem_done;
 		}
 		pr_info("Unable to allocate enough contiguous physical memory on Gen 1 VM. Using MMIO instead.\n");
-	} else {
+	} else if (IS_ENABLED(CONFIG_SYSFB)) {
 		base = screen_info.lfb_base;
 		size = screen_info.lfb_size;
 	}
@@ -1076,13 +1076,13 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
 getmem_done:
 	aperture_remove_conflicting_devices(base, size, KBUILD_MODNAME);
 
-	if (gen2vm) {
+	if (!gen2vm) {
+		pci_dev_put(pdev);
+	} else if (IS_ENABLED(CONFIG_SYSFB)) {
 		/* framebuffer is reallocated, clear screen_info to avoid misuse from kexec */
 		screen_info.lfb_size = 0;
 		screen_info.lfb_base = 0;
 		screen_info.orig_video_isVGA = 0;
-	} else {
-		pci_dev_put(pdev);
 	}
 
 	return 0;