1 files changed, 43 insertions, 0 deletions
diff --git a/drivers/video/fbdev/core/cfbmem.h b/drivers/video/fbdev/core/cfbmem.h
new file mode 100644
index 000000000000..ce2f5f751ea1
--- /dev/null
+++ b/drivers/video/fbdev/core/cfbmem.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0-only
+ *
+ *	I/O memory framebuffer access for drawing routines
+ *
+ *	Copyright (C) 2025 Zsolt Kajtar (soci@c64.rulez.org)
+ */
+
+/* keeps track of a bit address in framebuffer memory */
+struct fb_address {
+	void __iomem *address;
+	int bits;
+};
+
+/* initialize the bit address pointer to the beginning of the frame buffer */
+static inline struct fb_address fb_address_init(struct fb_info *p)
+{
+	void __iomem *base = p->screen_base;
+	struct fb_address ptr;
+
+	ptr.address = PTR_ALIGN_DOWN(base, BITS_PER_LONG / BITS_PER_BYTE);
+	ptr.bits = (base - ptr.address) * BITS_PER_BYTE;
+	return ptr;
+}
+
+/* framebuffer write access */
+static inline void fb_write_offset(unsigned long val, int offset, const struct fb_address *dst)
+{
+#if BITS_PER_LONG == 32
+	fb_writel(val, dst->address + offset * (BITS_PER_LONG / BITS_PER_BYTE));
+#else
+	fb_writeq(val, dst->address + offset * (BITS_PER_LONG / BITS_PER_BYTE));
+#endif
+}
+
+/* framebuffer read access */
+static inline unsigned long fb_read_offset(int offset, const struct fb_address *src)
+{
+#if BITS_PER_LONG == 32
+	return fb_readl(src->address + offset * (BITS_PER_LONG / BITS_PER_BYTE));
+#else
+	return fb_readq(src->address + offset * (BITS_PER_LONG / BITS_PER_BYTE));
+#endif
+}