fbdev: add remove_conflicting_pci_framebuffers()

Almost all PCI drivers using remove_conflicting_framebuffers() wrap it
with the same code.

v2: add kerneldoc for DRM helper
v3: propagate remove_conflicting_framebuffers() return value
  + move kerneldoc to where function is implemented

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/7db1c278276de420eb45a1b71d06b5eb6bbd49ef.1535810304.git.mirq-linux@rere.qmqm.pl

drivers/video/fbdev/core/fbmem.c

@@ -34,6 +34,7 @@
 #include <linux/fb.h>
 #include <linux/fbcon.h>
 #include <linux/mem_encrypt.h>
+#include <linux/pci.h>
 
 #include <asm/fb.h>
 
@@ -1830,6 +1831,40 @@ int remove_conflicting_framebuffers(struct apertures_struct *a,
 }
 EXPORT_SYMBOL(remove_conflicting_framebuffers);
 
+/**
+ * remove_conflicting_pci_framebuffers - remove firmware-configured framebuffers for PCI devices
+ * @pdev: PCI device
+ * @resource_id: index of PCI BAR configuring framebuffer memory
+ * @name: requesting driver name
+ *
+ * This function removes framebuffer devices (eg. initialized by firmware)
+ * using memory range configured for @pdev's BAR @resource_id.
+ *
+ * The function assumes that PCI device with shadowed ROM drives a primary
+ * display and so kicks out vga16fb.
+ */
+int remove_conflicting_pci_framebuffers(struct pci_dev *pdev, int res_id, const char *name)
+{
+	struct apertures_struct *ap;
+	bool primary = false;
+	int err;
+
+	ap = alloc_apertures(1);
+	if (!ap)
+		return -ENOMEM;
+
+	ap->ranges[0].base = pci_resource_start(pdev, res_id);
+	ap->ranges[0].size = pci_resource_len(pdev, res_id);
+#ifdef CONFIG_X86
+	primary = pdev->resource[PCI_ROM_RESOURCE].flags &
+					IORESOURCE_ROM_SHADOW;
+#endif
+	err = remove_conflicting_framebuffers(ap, name, primary);
+	kfree(ap);
+	return err;
+}
+EXPORT_SYMBOL(remove_conflicting_pci_framebuffers);
+
 /**
  *	register_framebuffer - registers a frame buffer device
  *	@fb_info: frame buffer info structure

include/drm/drm_fb_helper.h

@@ -615,4 +615,16 @@ drm_fb_helper_remove_conflicting_framebuffers(struct apertures_struct *a,
 #endif
 }
 
+static inline int
+drm_fb_helper_remove_conflicting_pci_framebuffers(struct pci_dev *pdev,
+						  int resource_id,
+						  const char *name)
+{
+#if IS_REACHABLE(CONFIG_FB)
+	return remove_conflicting_pci_framebuffers(pdev, resource_id, name);
+#else
+	return 0;
+#endif
+}
+
 #endif

include/linux/fb.h

@@ -632,6 +632,8 @@ extern ssize_t fb_sys_write(struct fb_info *info, const char __user *buf,
 extern int register_framebuffer(struct fb_info *fb_info);
 extern int unregister_framebuffer(struct fb_info *fb_info);
 extern int unlink_framebuffer(struct fb_info *fb_info);
+extern int remove_conflicting_pci_framebuffers(struct pci_dev *pdev, int res_id,
+					       const char *name);
 extern int remove_conflicting_framebuffers(struct apertures_struct *a,
 					   const char *name, bool primary);
 extern int fb_prepare_logo(struct fb_info *fb_info, int rotate);