/* SPDX-License-Identifier: GPL-2.0-only
 *
 *      Virtual 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 *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 *base = p->screen_buffer;
        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)
{
        unsigned long *mem = dst->address;

        mem[offset] = val;
}

/* framebuffer read access */
static inline unsigned long fb_read_offset(int offset, const struct fb_address *src)
{
        unsigned long *mem = src->address;

        return mem[offset];
}