// SPDX-License-Identifier: MIT

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

#include <drm/drm_drv.h>
#include <drm/drm_fbdev_shmem.h>
#include <drm/drm_fb_helper.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_gem_framebuffer_helper.h>
#include <drm/drm_gem_shmem_helper.h>
#include <drm/drm_print.h>

/*
 * struct fb_ops
 */

static int drm_fbdev_shmem_fb_open(struct fb_info *info, int user)
{
        struct drm_fb_helper *fb_helper = info->par;

        /* No need to take a ref for fbcon because it unbinds on unregister */
        if (user && !try_module_get(fb_helper->dev->driver->fops->owner))
                return -ENODEV;

        return 0;
}

static int drm_fbdev_shmem_fb_release(struct fb_info *info, int user)
{
        struct drm_fb_helper *fb_helper = info->par;

        if (user)
                module_put(fb_helper->dev->driver->fops->owner);

        return 0;
}

FB_GEN_DEFAULT_DEFERRED_SYSMEM_OPS(drm_fbdev_shmem,
                                   drm_fb_helper_damage_range,
                                   drm_fb_helper_damage_area);

static int drm_fbdev_shmem_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
{
        struct drm_fb_helper *fb_helper = info->par;
        struct drm_framebuffer *fb = fb_helper->fb;
        struct drm_gem_object *obj = drm_gem_fb_get_obj(fb, 0);
        struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);

        if (shmem->map_wc)
                vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);

        return fb_deferred_io_mmap(info, vma);
}

static void drm_fbdev_shmem_fb_destroy(struct fb_info *info)
{
        struct drm_fb_helper *fb_helper = info->par;

        if (!fb_helper->dev)
                return;

        fb_deferred_io_cleanup(info);
        drm_fb_helper_fini(fb_helper);

        drm_client_buffer_vunmap(fb_helper->buffer);
        drm_client_buffer_delete(fb_helper->buffer);
        drm_client_release(&fb_helper->client);
}

static const struct fb_ops drm_fbdev_shmem_fb_ops = {
        .owner = THIS_MODULE,
        .fb_open = drm_fbdev_shmem_fb_open,
        .fb_release = drm_fbdev_shmem_fb_release,
        __FB_DEFAULT_DEFERRED_OPS_RDWR(drm_fbdev_shmem),
        DRM_FB_HELPER_DEFAULT_OPS,
        __FB_DEFAULT_DEFERRED_OPS_DRAW(drm_fbdev_shmem),
        .fb_mmap = drm_fbdev_shmem_fb_mmap,
        .fb_destroy = drm_fbdev_shmem_fb_destroy,
};

static struct page *drm_fbdev_shmem_get_page(struct fb_info *info, unsigned long offset)
{
        struct drm_fb_helper *fb_helper = info->par;
        struct drm_framebuffer *fb = fb_helper->fb;
        struct drm_gem_object *obj = drm_gem_fb_get_obj(fb, 0);
        struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
        unsigned int i = offset >> PAGE_SHIFT;
        struct page *page;

        if (fb_WARN_ON_ONCE(info, offset > obj->size))
                return NULL;

        page = shmem->pages[i]; // protected by active vmap
        if (page)
                get_page(page);
        fb_WARN_ON_ONCE(info, !page);

        return page;
}

/*
 * struct drm_fb_helper
 */

static int drm_fbdev_shmem_helper_fb_dirty(struct drm_fb_helper *helper,
                                           struct drm_clip_rect *clip)
{
        struct drm_device *dev = helper->dev;
        int ret;

        /* Call damage handlers only if necessary */
        if (!(clip->x1 < clip->x2 && clip->y1 < clip->y2))
                return 0;

        if (helper->fb->funcs->dirty) {
                ret = helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, clip, 1);
                if (drm_WARN_ONCE(dev, ret, "Dirty helper failed: ret=%d\n", ret))
                        return ret;
        }

        return 0;
}

static const struct drm_fb_helper_funcs drm_fbdev_shmem_helper_funcs = {
        .fb_dirty = drm_fbdev_shmem_helper_fb_dirty,
};

/*
 * struct drm_driver
 */

int drm_fbdev_shmem_driver_fbdev_probe(struct drm_fb_helper *fb_helper,
                                       struct drm_fb_helper_surface_size *sizes)
{
        struct drm_client_dev *client = &fb_helper->client;
        struct drm_device *dev = fb_helper->dev;
        struct fb_info *info = fb_helper->info;
        struct drm_client_buffer *buffer;
        struct drm_gem_shmem_object *shmem;
        struct drm_framebuffer *fb;
        u32 format;
        struct iosys_map map;
        int ret;

        drm_dbg_kms(dev, "surface width(%d), height(%d) and bpp(%d)\n",
                    sizes->surface_width, sizes->surface_height,
                    sizes->surface_bpp);

        format = drm_driver_legacy_fb_format(dev, sizes->surface_bpp, sizes->surface_depth);
        buffer = drm_client_buffer_create_dumb(client, sizes->surface_width,
                                               sizes->surface_height, format);
        if (IS_ERR(buffer))
                return PTR_ERR(buffer);
        shmem = to_drm_gem_shmem_obj(buffer->gem);

        fb = buffer->fb;

        ret = drm_client_buffer_vmap(buffer, &map);
        if (ret) {
                goto err_drm_client_buffer_delete;
        } else if (drm_WARN_ON(dev, map.is_iomem)) {
                ret = -ENODEV; /* I/O memory not supported; use generic emulation */
                goto err_drm_client_buffer_delete;
        }

        fb_helper->funcs = &drm_fbdev_shmem_helper_funcs;
        fb_helper->buffer = buffer;
        fb_helper->fb = fb;

        drm_fb_helper_fill_info(info, fb_helper, sizes);

        info->fbops = &drm_fbdev_shmem_fb_ops;

        /* screen */
        info->flags |= FBINFO_VIRTFB; /* system memory */
        if (!shmem->map_wc)
                info->flags |= FBINFO_READS_FAST; /* signal caching */
        info->screen_size = sizes->surface_height * fb->pitches[0];
        info->screen_buffer = map.vaddr;
        info->fix.smem_len = info->screen_size;

        /* deferred I/O */
        fb_helper->fbdefio.delay = HZ / 20;
        fb_helper->fbdefio.get_page = drm_fbdev_shmem_get_page;
        fb_helper->fbdefio.deferred_io = drm_fb_helper_deferred_io;

        info->fbdefio = &fb_helper->fbdefio;
        ret = fb_deferred_io_init(info);
        if (ret)
                goto err_drm_client_buffer_vunmap;

        return 0;

err_drm_client_buffer_vunmap:
        fb_helper->fb = NULL;
        fb_helper->buffer = NULL;
        drm_client_buffer_vunmap(buffer);
err_drm_client_buffer_delete:
        drm_client_buffer_delete(buffer);
        return ret;
}
EXPORT_SYMBOL(drm_fbdev_shmem_driver_fbdev_probe);