cfbmem.h

 1/* SPDX-License-Identifier: GPL-2.0-only
 2 *
 3 *	I/O memory framebuffer access for drawing routines
 4 *
 5 *	Copyright (C) 2025 Zsolt Kajtar (soci@c64.rulez.org)
 6 */
 7
 8/* keeps track of a bit address in framebuffer memory */
 9struct fb_address {
10	void __iomem *address;
11	int bits;
12};
13
14/* initialize the bit address pointer to the beginning of the frame buffer */
15static inline struct fb_address fb_address_init(struct fb_info *p)
16{
17	void __iomem *base = p->screen_base;
18	struct fb_address ptr;
19
20	ptr.address = PTR_ALIGN_DOWN(base, BITS_PER_LONG / BITS_PER_BYTE);
21	ptr.bits = (base - ptr.address) * BITS_PER_BYTE;
22	return ptr;
23}
24
25/* framebuffer write access */
26static inline void fb_write_offset(unsigned long val, int offset, const struct fb_address *dst)
27{
28#if BITS_PER_LONG == 32
29	fb_writel(val, dst->address + offset * (BITS_PER_LONG / BITS_PER_BYTE));
30#else
31	fb_writeq(val, dst->address + offset * (BITS_PER_LONG / BITS_PER_BYTE));
32#endif
33}
34
35/* framebuffer read access */
36static inline unsigned long fb_read_offset(int offset, const struct fb_address *src)
37{
38#if BITS_PER_LONG == 32
39	return fb_readl(src->address + offset * (BITS_PER_LONG / BITS_PER_BYTE));
40#else
41	return fb_readq(src->address + offset * (BITS_PER_LONG / BITS_PER_BYTE));
42#endif
43}