[PATCH v2 01/19] fbdev: Prepare generic architecture helpers

Generic implementations of fb_pgprotect() and fb_is_primary_device()
have been in the source code for a long time. Prepare the header file
to make use of them.

Improve the code by using an inline function for fb_pgprotect()
and by removing include statements. The default mode set by
fb_pgprotect() is now writecombine, which is what most platforms
want.

Symbols are protected by preprocessor guards. Architectures that
provide a symbol need to define a preprocessor token of the same
name and value. Otherwise the header file will provide a generic
implementation. This pattern has been taken from <asm/io.h>.

v2:
	*  use writecombine mappings by default (Arnd)

Signed-off-by: Thomas Zimmermann <[email protected]>
---
 include/asm-generic/fb.h | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/fb.h b/include/asm-generic/fb.h
index f9f18101ed36..631d97c507ca 100644
--- a/include/asm-generic/fb.h
+++ b/include/asm-generic/fb.h
@@ -1,13 +1,32 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+
 #ifndef __ASM_GENERIC_FB_H_
 #define __ASM_GENERIC_FB_H_
-#include <linux/fb.h>
 
-#define fb_pgprotect(...) do {} while (0)
+/*
+ * Only include this header file from your architecture's <asm/fb.h>.
+ */
+
+#include <asm/page.h>
+
+struct fb_info;
+struct file;
+
+#ifndef fb_pgprotect
+#define fb_pgprotect fb_pgprotect
+static inline void fb_pgprotect(struct file *file, struct vm_area_struct *vma,
+				unsigned long off)
+{
+	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+}
+#endif
 
+#ifndef fb_is_primary_device
+#define fb_is_primary_device fb_is_primary_device
 static inline int fb_is_primary_device(struct fb_info *info)
 {
 	return 0;
 }
+#endif
 
 #endif /* __ASM_GENERIC_FB_H_ */
-- 
2.40.0