// SPDX-License-Identifier: GPL-2.0

#include <linux/export.h>
#include <linux/fb.h>
#include <linux/module.h>
#include <linux/uaccess.h>

ssize_t fb_io_read(struct fb_info *info, char __user *buf, size_t count, loff_t *ppos)
{
        unsigned long p = *ppos;
        u8 *buffer, *dst;
        u8 __iomem *src;
        int c, cnt = 0, err = 0;
        unsigned long total_size, trailing;

        if (info->flags & FBINFO_VIRTFB)
                fb_warn_once(info, "Framebuffer is not in I/O address space.");

        if (!info->screen_base)
                return -ENODEV;

        total_size = info->screen_size;

        if (total_size == 0)
                total_size = info->fix.smem_len;

        if (p >= total_size)
                return 0;

        if (count >= total_size)
                count = total_size;

        if (count + p > total_size)
                count = total_size - p;

        buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
                         GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;

        src = (u8 __iomem *) (info->screen_base + p);

        if (info->fbops->fb_sync)
                info->fbops->fb_sync(info);

        while (count) {
                c  = (count > PAGE_SIZE) ? PAGE_SIZE : count;
                dst = buffer;
                fb_memcpy_fromio(dst, src, c);
                dst += c;
                src += c;

                trailing = copy_to_user(buf, buffer, c);
                if (trailing == c) {
                        err = -EFAULT;
                        break;
                }
                c -= trailing;

                *ppos += c;
                buf += c;
                cnt += c;
                count -= c;
        }

        kfree(buffer);

        return cnt ? cnt : err;
}
EXPORT_SYMBOL(fb_io_read);

ssize_t fb_io_write(struct fb_info *info, const char __user *buf, size_t count, loff_t *ppos)
{
        unsigned long p = *ppos;
        u8 *buffer, *src;
        u8 __iomem *dst;
        int c, cnt = 0, err = 0;
        unsigned long total_size, trailing;

        if (info->flags & FBINFO_VIRTFB)
                fb_warn_once(info, "Framebuffer is not in I/O address space.");

        if (!info->screen_base)
                return -ENODEV;

        total_size = info->screen_size;

        if (total_size == 0)
                total_size = info->fix.smem_len;

        if (p > total_size)
                return -EFBIG;

        if (count > total_size) {
                err = -EFBIG;
                count = total_size;
        }

        if (count + p > total_size) {
                if (!err)
                        err = -ENOSPC;

                count = total_size - p;
        }

        buffer = kmalloc((count > PAGE_SIZE) ? PAGE_SIZE : count,
                         GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;

        dst = (u8 __iomem *) (info->screen_base + p);

        if (info->fbops->fb_sync)
                info->fbops->fb_sync(info);

        while (count) {
                c = (count > PAGE_SIZE) ? PAGE_SIZE : count;
                src = buffer;

                trailing = copy_from_user(src, buf, c);
                if (trailing == c) {
                        err = -EFAULT;
                        break;
                }
                c -= trailing;

                fb_memcpy_toio(dst, src, c);
                dst += c;
                src += c;
                *ppos += c;
                buf += c;
                cnt += c;
                count -= c;
        }

        kfree(buffer);

        return (cnt) ? cnt : err;
}
EXPORT_SYMBOL(fb_io_write);

int fb_io_mmap(struct fb_info *info, struct vm_area_struct *vma)
{
        unsigned long start = info->fix.smem_start;
        u32 len = info->fix.smem_len;
        unsigned long mmio_pgoff = PAGE_ALIGN((start & ~PAGE_MASK) + len) >> PAGE_SHIFT;

        if (info->flags & FBINFO_VIRTFB)
                fb_warn_once(info, "Framebuffer is not in I/O address space.");

        /*
         * This can be either the framebuffer mapping, or if pgoff points
         * past it, the mmio mapping.
         */
        if (vma->vm_pgoff >= mmio_pgoff) {
                if (info->var.accel_flags)
                        return -EINVAL;

                vma->vm_pgoff -= mmio_pgoff;
                start = info->fix.mmio_start;
                len = info->fix.mmio_len;
        }

        vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
        vma->vm_page_prot = pgprot_framebuffer(vma->vm_page_prot, vma->vm_start,
                                               vma->vm_end, start);

        return vm_iomap_memory(vma, start, len);
}
EXPORT_SYMBOL(fb_io_mmap);

MODULE_DESCRIPTION("Fbdev helpers for framebuffers in I/O memory");
MODULE_LICENSE("GPL");