parisc/stifb: Implement fb_is_primary_device()

Implement fb_is_primary_device() function, so that fbcon detects if this
framebuffer belongs to the default graphics card which was used to start
the system.
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org   # v5.10+

arch/parisc/include/asm/fb.h

@@ -12,9 +12,13 @@ static inline void fb_pgprotect(struct file *file, struct vm_area_struct *vma,
 	pgprot_val(vma->vm_page_prot) |= _PAGE_NO_CACHE;
 }
 
+#if defined(CONFIG_STI_CONSOLE) || defined(CONFIG_FB_STI)
+int fb_is_primary_device(struct fb_info *info);
+#else
 static inline int fb_is_primary_device(struct fb_info *info)
 {
 	return 0;
 }
+#endif
 
 #endif /* _ASM_FB_H_ */

drivers/video/console/sticore.c

@@ -30,6 +30,7 @@
 #include <asm/pdc.h>
 #include <asm/cacheflush.h>
 #include <asm/grfioctl.h>
+#include <asm/fb.h>
 
 #include "../fbdev/sticore.h"
 
@@ -1127,6 +1128,22 @@ int sti_call(const struct sti_struct *sti, unsigned long func,
 	return ret;
 }
 
+/* check if given fb_info is the primary device */
+int fb_is_primary_device(struct fb_info *info)
+{
+	struct sti_struct *sti;
+
+	sti = sti_get_rom(0);
+
+	/* if no built-in graphics card found, allow any fb driver as default */
+	if (!sti)
+		return true;
+
+	/* return true if it's the default built-in framebuffer driver */
+	return (sti->info == info);
+}
+EXPORT_SYMBOL(fb_is_primary_device);
+
 MODULE_AUTHOR("Philipp Rumpf, Helge Deller, Thomas Bogendoerfer");
 MODULE_DESCRIPTION("Core STI driver for HP's NGLE series graphics cards in HP PARISC machines");
 MODULE_LICENSE("GPL v2");

drivers/video/fbdev/stifb.c

@@ -1358,11 +1358,11 @@ static int __init stifb_init_fb(struct sti_struct *sti, int bpp_pref)
 		goto out_err3;
 	}
 
+	/* save for primary gfx device detection & unregister_framebuffer() */
+	sti->info = info;
 	if (register_framebuffer(&fb->info) < 0)
 		goto out_err4;
 
-	sti->info = info; /* save for unregister_framebuffer() */
-
 	fb_info(&fb->info, "%s %dx%d-%d frame buffer device, %s, id: %04x, mmio: 0x%04lx\n",
 		fix->id,
 		var->xres,