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Subject: [Intel-gfx] [RFC v3 10/12] drm/client: Add fbdev emulation client
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This adds generic fbdev emulation for drivers that support the
dumb buffer API. No fbdev code is necessary in the driver.

Differences from drm_fb_helper:
- The backing buffer is created when the first fd is opened.
- Supports changing the mode from userspace.
- Doesn't restore on lastclose if there is no fd/fbcon open.
- Supports changing the buffer size (yres_virtual) from userspace before
  the fd is opened (double/trippel/... buffering).
- Panning is only supported as page flipping, so no partial offset.
- Supports real page flipping with FBIO_WAITFORVSYNC waiting on the
  actual flip.
- Supports framebuffer flushing for fbcon on buffers that doesn't support
  fbdev deferred I/O (shmem). mmap doesn't work but fbcon does.

TODO:
- suspend/resume
- sysrq
- Look more into plane format selection/support.
- Need a way for the driver to say that it wants generic fbdev emulation.
  The client .new hook is run in drm_dev_register() which is before
  drivers set up fbdev themselves. So the client can't look at
  drm_device->fb_helper to find out.
- Do we need to support FB_VISUAL_PSEUDOCOLOR?

TROUBLE:
- fbcon can't handle fb_open returning an error, it just heads on. This
  results in a NULL deref in fbcon_init(). fbcon/vt is awful when it
  comes to error handling. It doesn't look to be easily fixed, so I guess
  a buffer has to be pre-allocated to ensure health and safety.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---
 drivers/gpu/drm/client/Kconfig     |  16 +
 drivers/gpu/drm/client/Makefile    |   2 +
 drivers/gpu/drm/client/drm_fbdev.c | 997 +++++++++++++++++++++++++++++++++++++
 3 files changed, 1015 insertions(+)
 create mode 100644 drivers/gpu/drm/client/drm_fbdev.c

diff --git a/drivers/gpu/drm/client/Kconfig b/drivers/gpu/drm/client/Kconfig
index 4bb8e4655ff7..73902ab44c75 100644
--- a/drivers/gpu/drm/client/Kconfig
+++ b/drivers/gpu/drm/client/Kconfig
@@ -1,4 +1,20 @@
 menu "DRM Clients"
 	depends on DRM
 
+config DRM_CLIENT_FBDEV
+	tristate "Generic fbdev emulation"
+	depends on DRM
+	select FB
+	select FRAMEBUFFER_CONSOLE if !EXPERT
+	select FRAMEBUFFER_CONSOLE_DETECT_PRIMARY if FRAMEBUFFER_CONSOLE
+	select FB_SYS_FOPS
+	select FB_SYS_FILLRECT
+	select FB_SYS_COPYAREA
+	select FB_SYS_IMAGEBLIT
+	select FB_DEFERRED_IO
+	select FB_MODE_HELPERS
+	select VIDEOMODE_HELPERS
+	help
+	  Generic fbdev emulation
+
 endmenu
diff --git a/drivers/gpu/drm/client/Makefile b/drivers/gpu/drm/client/Makefile
index f66554cd5c45..3ff694429dec 100644
--- a/drivers/gpu/drm/client/Makefile
+++ b/drivers/gpu/drm/client/Makefile
@@ -1 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_DRM_CLIENT_FBDEV) += drm_fbdev.o
diff --git a/drivers/gpu/drm/client/drm_fbdev.c b/drivers/gpu/drm/client/drm_fbdev.c
new file mode 100644
index 000000000000..e28416d72de1
--- /dev/null
+++ b/drivers/gpu/drm/client/drm_fbdev.c
@@ -0,0 +1,997 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright 2018 Noralf Trønnes
+
+#include <linux/console.h>
+#include <linux/dma-buf.h>
+#include <linux/fb.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include <video/videomode.h>
+
+#include <drm/drm_client.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_modes.h>
+#include <drm/drm_print.h>
+
+struct drm_fbdev {
+	struct mutex lock;
+
+	struct drm_client_dev *client;
+	struct drm_client_display *display;
+
+	unsigned int open_count;
+	struct drm_client_buffer *buffer;
+	bool page_flip_sent;
+	u32 curr_fb;
+
+	struct fb_info *info;
+	u32 pseudo_palette[17];
+
+	bool flush;
+	bool defio_no_flushing;
+	struct drm_clip_rect dirty_clip;
+	spinlock_t dirty_lock;
+	struct work_struct dirty_work;
+};
+
+static int drm_fbdev_mode_to_fb_mode(struct drm_device *dev,
+				     struct drm_mode_modeinfo *mode,
+				     struct fb_videomode *fb_mode)
+{
+	struct drm_display_mode display_mode = { };
+	struct videomode videomode = { };
+	int ret;
+
+	ret = drm_mode_convert_umode(dev, &display_mode, mode);
+	if (ret)
+		return ret;
+
+	memset(fb_mode, 0, sizeof(*fb_mode));
+	drm_display_mode_to_videomode(&display_mode, &videomode);
+	fb_videomode_from_videomode(&videomode, fb_mode);
+
+	return 0;
+}
+
+static void drm_fbdev_destroy_modelist(struct fb_info *info)
+{
+	struct fb_modelist *modelist, *tmp;
+
+	list_for_each_entry_safe(modelist, tmp, &info->modelist, list) {
+		kfree(modelist->mode.name);
+		list_del(&modelist->list);
+		kfree(modelist);
+	}
+}
+
+static void drm_fbdev_use_first_mode(struct fb_info *info)
+{
+	struct fb_modelist *modelist;
+
+	modelist = list_first_entry(&info->modelist, struct fb_modelist, list);
+	fb_videomode_to_var(&info->var, &modelist->mode);
+	info->mode = &modelist->mode;
+}
+
+static struct drm_mode_modeinfo *drm_fbdev_get_drm_mode(struct drm_fbdev *fbdev)
+{
+	struct drm_mode_modeinfo *mode_pos, *mode = NULL;
+	struct fb_info *info = fbdev->info;
+	struct fb_videomode tmp;
+
+	mutex_lock(&fbdev->display->modes_lock);
+	drm_client_display_for_each_mode(fbdev->display, mode_pos) {
+		if (drm_fbdev_mode_to_fb_mode(fbdev->client->dev, mode_pos, &tmp))
+			continue;
+		if (fb_mode_is_equal(info->mode, &tmp)) {
+			mode = mode_pos;
+			break;
+		}
+	}
+	mutex_unlock(&fbdev->display->modes_lock);
+
+	return mode;
+}
+
+/* Return number of modes or negative error */
+static int drm_fbdev_sync_modes(struct drm_fbdev *fbdev, bool force)
+{
+	struct fb_info *info = fbdev->info;
+	struct drm_mode_modeinfo *mode;
+	struct fb_videomode fb_mode;
+	bool changed;
+
+	struct fb_modelist *fbdev_modelist;
+	int num_modes;
+
+	num_modes = drm_client_display_update_modes(fbdev->display, &changed);
+	if (num_modes <= 0)
+		return num_modes;
+
+	if (!info)
+		return num_modes;
+
+	if (!force && !changed)
+		return num_modes;
+
+	drm_fbdev_destroy_modelist(info);
+
+	mutex_lock(&fbdev->display->modes_lock);
+	drm_client_display_for_each_mode(fbdev->display, mode) {
+		if (drm_fbdev_mode_to_fb_mode(fbdev->client->dev, mode, &fb_mode)) {
+			num_modes--;
+			continue;
+		}
+
+		fbdev_modelist = kzalloc(sizeof(*fbdev_modelist), GFP_KERNEL);
+		if (!fbdev_modelist) {
+			drm_fbdev_destroy_modelist(info);
+			mutex_unlock(&fbdev->display->modes_lock);
+			return -ENOMEM;
+		}
+
+		fbdev_modelist->mode = fb_mode;
+		fbdev_modelist->mode.name = kstrndup(mode->name,
+						     DRM_DISPLAY_MODE_LEN,
+						     GFP_KERNEL);
+
+		if (mode->type & DRM_MODE_TYPE_PREFERRED)
+			fbdev_modelist->mode.flag |= FB_MODE_IS_FIRST;
+
+		list_add_tail(&fbdev_modelist->list, &info->modelist);
+	}
+	mutex_unlock(&fbdev->display->modes_lock);
+
+	if (!fbdev->open_count)
+		drm_fbdev_use_first_mode(info);
+
+	return num_modes;
+}
+
+static void drm_fbdev_format_fill_var(u32 format, struct fb_var_screeninfo *var)
+{
+	switch (format) {
+	case DRM_FORMAT_XRGB1555:
+		var->red.offset = 10;
+		var->red.length = 5;
+		var->green.offset = 5;
+		var->green.length = 5;
+		var->blue.offset = 0;
+		var->blue.length = 5;
+		var->transp.offset = 0;
+		var->transp.length = 0;
+		break;
+	case DRM_FORMAT_ARGB1555:
+		var->red.offset = 10;
+		var->red.length = 5;
+		var->green.offset = 5;
+		var->green.length = 5;
+		var->blue.offset = 0;
+		var->blue.length = 5;
+		var->transp.offset = 15;
+		var->transp.length = 1;
+		break;
+	case DRM_FORMAT_RGB565:
+		var->red.offset = 11;
+		var->red.length = 5;
+		var->green.offset = 5;
+		var->green.length = 6;
+		var->blue.offset = 0;
+		var->blue.length = 5;
+		var->transp.offset = 0;
+		var->transp.length = 0;
+		break;
+	case DRM_FORMAT_RGB888:
+	case DRM_FORMAT_XRGB8888:
+		var->red.offset = 16;
+		var->red.length = 8;
+		var->green.offset = 8;
+		var->green.length = 8;
+		var->blue.offset = 0;
+		var->blue.length = 8;
+		var->transp.offset = 0;
+		var->transp.length = 0;
+		break;
+	case DRM_FORMAT_ARGB8888:
+		var->red.offset = 16;
+		var->red.length = 8;
+		var->green.offset = 8;
+		var->green.length = 8;
+		var->blue.offset = 0;
+		var->blue.length = 8;
+		var->transp.offset = 24;
+		var->transp.length = 8;
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		return;
+	}
+
+	var->colorspace = 0;
+	var->grayscale = 0;
+	var->nonstd = 0;
+}
+
+int drm_fbdev_var_to_format(struct fb_var_screeninfo *var, u32 *format)
+{
+	switch (var->bits_per_pixel) {
+	case 15:
+		*format = DRM_FORMAT_ARGB1555;
+		break;
+	case 16:
+		if (var->green.length != 5)
+			*format = DRM_FORMAT_RGB565;
+		else if (var->transp.length > 0)
+			*format = DRM_FORMAT_ARGB1555;
+		else
+			*format = DRM_FORMAT_XRGB1555;
+		break;
+	case 24:
+		*format = DRM_FORMAT_RGB888;
+		break;
+	case 32:
+		if (var->transp.length > 0)
+			*format = DRM_FORMAT_ARGB8888;
+		else
+			*format = DRM_FORMAT_XRGB8888;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void drm_fbdev_dirty_work(struct work_struct *work)
+{
+	struct drm_fbdev *fbdev = container_of(work, struct drm_fbdev,
+					       dirty_work);
+	struct drm_clip_rect *clip = &fbdev->dirty_clip;
+	struct drm_clip_rect clip_copy;
+	unsigned long flags;
+
+	spin_lock_irqsave(&fbdev->dirty_lock, flags);
+	clip_copy = *clip;
+	clip->x1 = clip->y1 = ~0;
+	clip->x2 = clip->y2 = 0;
+	spin_unlock_irqrestore(&fbdev->dirty_lock, flags);
+
+	/* call dirty callback only when it has been really touched */
+	if (clip_copy.x1 < clip_copy.x2 && clip_copy.y1 < clip_copy.y2)
+		drm_client_display_flush(fbdev->display, fbdev->curr_fb,
+					 &clip_copy, 1);
+}
+
+static void drm_fbdev_dirty(struct fb_info *info, u32 x, u32 y,
+			    u32 width, u32 height)
+{
+	struct drm_fbdev *fbdev = info->par;
+	struct drm_clip_rect *clip = &fbdev->dirty_clip;
+	unsigned long flags;
+
+	if (!fbdev->flush)
+		return;
+
+	spin_lock_irqsave(&fbdev->dirty_lock, flags);
+	clip->x1 = min_t(u32, clip->x1, x);
+	clip->y1 = min_t(u32, clip->y1, y);
+	clip->x2 = max_t(u32, clip->x2, x + width);
+	clip->y2 = max_t(u32, clip->y2, y + height);
+	spin_unlock_irqrestore(&fbdev->dirty_lock, flags);
+
+	schedule_work(&fbdev->dirty_work);
+}
+
+static void drm_fbdev_deferred_io(struct fb_info *info,
+				  struct list_head *pagelist)
+{
+	struct drm_fbdev *fbdev = info->par;
+	unsigned long start, end, min, max;
+	struct page *page;
+	u32 y1, y2;
+
+	/* Is userspace doing explicit pageflip flushing? */
+	if (fbdev->defio_no_flushing)
+		return;
+
+	min = ULONG_MAX;
+	max = 0;
+	list_for_each_entry(page, pagelist, lru) {
+		start = page->index << PAGE_SHIFT;
+		end = start + PAGE_SIZE;
+		min = min(min, start);
+		max = max(max, end);
+	}
+
+	if (min < max) {
+		y1 = min / info->fix.line_length;
+		y2 = DIV_ROUND_UP(max, info->fix.line_length);
+		y2 = min(y2, info->var.yres);
+		drm_fbdev_dirty(info, 0, y1, info->var.xres, y2 - y1);
+	}
+}
+
+static struct fb_deferred_io drm_fbdev_fbdefio = {
+	.delay		= HZ / 20,
+	.deferred_io	= drm_fbdev_deferred_io,
+};
+
+static int
+drm_fbdev_fb_mmap_notsupp(struct fb_info *info, struct vm_area_struct *vma)
+{
+	return -ENOTSUPP;
+}
+
+static void drm_fbdev_delete_buffer(struct drm_fbdev *fbdev)
+{
+	struct fb_info *info = fbdev->info;
+
+	if (info->fbdefio) {
+		/* Stop worker and clear page->mapping */
+		fb_deferred_io_cleanup(info);
+		info->fbdefio = NULL;
+	}
+	if (fbdev->flush) {
+		fbdev->flush = false;
+		cancel_work_sync(&fbdev->dirty_work);
+	}
+
+	drm_client_buffer_rmfb(fbdev->buffer);
+	drm_client_buffer_delete(fbdev->buffer);
+
+	fbdev->buffer = NULL;
+	fbdev->curr_fb = 0;
+	fbdev->page_flip_sent = false;
+	info->screen_buffer = NULL;
+	info->screen_size = 0;
+	info->fix.smem_len = 0;
+	info->fix.line_length = 0;
+}
+
+/* Temporary hack to make tinydrm work before converting to vmalloc buffers */
+static int drm_fbdev_cma_deferred_io_mmap(struct fb_info *info,
+					  struct vm_area_struct *vma)
+{
+	fb_deferred_io_mmap(info, vma);
+	vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+
+	return 0;
+}
+
+static int drm_fbdev_create_buffer(struct drm_fbdev *fbdev)
+{
+	struct drm_client_dev *client = fbdev->client;
+	struct fb_info *info = fbdev->info;
+	struct drm_client_buffer *buffer;
+	struct drm_mode_modeinfo *mode;
+	u32 format;
+	int ret;
+
+	ret = drm_fbdev_var_to_format(&info->var, &format);
+	if (ret)
+		return ret;
+
+	buffer = drm_client_buffer_create(client, info->var.xres_virtual,
+					  info->var.yres_virtual, format);
+	if (IS_ERR(buffer))
+		return PTR_ERR(buffer);
+
+	mode = drm_fbdev_get_drm_mode(fbdev);
+	if (!mode)
+		return -EINVAL;
+
+	ret = drm_client_buffer_addfb(buffer, mode);
+	if (ret)
+		goto err_free_buffer;
+
+	fbdev->curr_fb = buffer->fb_ids[0];
+
+	if (drm_mode_can_dirtyfb(client->dev, fbdev->curr_fb, client->file)) {
+		fbdev->flush = true;
+/*		if (is_vmalloc_addr(buffer->vaddr)) { */
+/* Temporary hack for testing on tinydrm before it has moved to vmalloc */
+		if (1) {
+			fbdev->dirty_clip.x1 = fbdev->dirty_clip.y1 = ~0;
+			fbdev->dirty_clip.x2 = fbdev->dirty_clip.y2 = 0;
+			info->fbdefio = &drm_fbdev_fbdefio;
+
+			/* tinydrm hack */
+			info->fix.smem_start = page_to_phys(virt_to_page(buffer->vaddr));
+
+			fb_deferred_io_init(info);
+			/* tinydrm hack */
+			info->fbops->fb_mmap = drm_fbdev_cma_deferred_io_mmap;
+		} else {
+			info->fbops->fb_mmap = drm_fbdev_fb_mmap_notsupp;
+		}
+	}
+
+	fbdev->buffer = buffer;
+	info->screen_buffer = buffer->vaddr;
+	info->screen_size = buffer->size;
+	info->fix.smem_len = buffer->size;
+	info->fix.line_length = buffer->pitch;
+
+	return 0;
+
+err_free_buffer:
+	drm_client_buffer_delete(buffer);
+
+	return ret;
+}
+
+static int drm_fbdev_fb_open(struct fb_info *info, int user)
+{
+	struct drm_fbdev *fbdev = info->par;
+	int ret = 0;
+
+	DRM_DEV_DEBUG_KMS(fbdev->client->dev->dev, "\n");
+
+	mutex_lock(&fbdev->lock);
+
+	if (!fbdev->display) {
+		ret = -ENODEV;
+		goto out_unlock;
+	}
+
+	if (!fbdev->open_count) {
+		/* Pipeline is disabled, make sure it's forced on */
+		info->var.activate = FB_ACTIVATE_NOW | FB_ACTIVATE_FORCE;
+		ret = drm_fbdev_create_buffer(fbdev);
+		if (ret)
+			goto out_unlock;
+	}
+
+	fbdev->open_count++;
+
+out_unlock:
+	mutex_unlock(&fbdev->lock);
+
+	if (ret)
+		DRM_DEV_ERROR(fbdev->client->dev->dev, "fb_open failed (%d)\n", ret);
+
+	return ret;
+}
+
+static int drm_fbdev_fb_release(struct fb_info *info, int user)
+{
+	struct drm_fbdev *fbdev = info->par;
+
+	DRM_DEV_DEBUG_KMS(fbdev->client->dev->dev, "\n");
+	mutex_lock(&fbdev->lock);
+
+	if (--fbdev->open_count == 0) {
+		drm_client_display_dpms(fbdev->display, DRM_MODE_DPMS_OFF);
+		drm_fbdev_delete_buffer(fbdev);
+	}
+
+	fbdev->defio_no_flushing = false;
+
+	mutex_unlock(&fbdev->lock);
+
+	return 0;
+}
+
+static ssize_t drm_fbdev_fb_write(struct fb_info *info, const char __user *buf,
+				  size_t count, loff_t *ppos)
+{
+	ssize_t ret;
+
+	ret = fb_sys_write(info, buf, count, ppos);
+	if (ret > 0)
+		drm_fbdev_dirty(info, 0, 0, info->var.xres, info->var.yres);
+
+	return ret;
+}
+
+static void
+drm_fbdev_fb_fillrect(struct fb_info *info, const struct fb_fillrect *rect)
+{
+	sys_fillrect(info, rect);
+	drm_fbdev_dirty(info, rect->dx, rect->dy, rect->width, rect->height);
+}
+
+static void
+drm_fbdev_fb_copyarea(struct fb_info *info, const struct fb_copyarea *area)
+{
+	sys_copyarea(info, area);
+	drm_fbdev_dirty(info, area->dx, area->dy, area->width, area->height);
+}
+
+static void
+drm_fbdev_fb_imageblit(struct fb_info *info, const struct fb_image *image)
+{
+	sys_imageblit(info, image);
+	drm_fbdev_dirty(info, image->dx, image->dy, image->width, image->height);
+}
+
+static int
+drm_fbdev_fb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
+{
+	u32 new_format, old_format, yres_virtual;
+	struct drm_fbdev *fbdev = info->par;
+	const struct fb_videomode *fb_mode;
+	bool is_open;
+	int ret;
+
+	mutex_lock(&fbdev->lock);
+	is_open = fbdev->open_count;
+	mutex_unlock(&fbdev->lock);
+
+	if (!is_open && in_dbg_master())
+		return -EINVAL;
+
+	/* Can be called from sysfs */
+	if (is_open && (var->xres_virtual > fbdev->buffer->width ||
+	    var->yres_virtual > fbdev->buffer->height)) {
+		DRM_DEBUG_KMS("Cannot increase virtual resolution while open\n");
+		return -EBUSY;
+	}
+
+	if (var->xres > var->xres_virtual || var->yres > var->yres_virtual) {
+		DRM_DEBUG_KMS("Requested width/height to big: %dx%d > virtual %dx%d\n",
+			      var->xres, var->yres, var->xres_virtual,
+			      var->yres_virtual);
+		return -EINVAL;
+	}
+
+	ret = drm_fbdev_var_to_format(var, &new_format);
+	if (ret) {
+		DRM_DEBUG_KMS("Unsupported format\n");
+		return -EINVAL;
+	}
+
+	ret = drm_fbdev_var_to_format(&info->var, &old_format);
+	if (ret)
+		return ret;
+
+	if (new_format != old_format && is_open) {
+		DRM_DEBUG_KMS("Cannot change format while open\n");
+		return -EBUSY;
+	}
+
+	drm_fbdev_format_fill_var(new_format, var);
+
+	fb_mode = fb_find_best_mode(var, &info->modelist);
+	if (!fb_mode)
+		return -EINVAL;
+
+	yres_virtual = var->yres_virtual;
+	fb_videomode_to_var(var, fb_mode);
+	var->yres_virtual = yres_virtual;
+
+	return 0;
+}
+
+static int drm_fbdev_fb_set_par(struct fb_info *info)
+{
+	struct drm_fbdev *fbdev = info->par;
+	const struct fb_videomode *fb_mode;
+	struct drm_mode_modeinfo *mode;
+	bool mode_changed;
+	int ret;
+
+	mutex_lock(&fbdev->lock);
+
+	if (!fbdev->open_count) {
+		ret = 0;
+		goto out_unlock;
+	}
+
+	fb_mode = fb_match_mode(&info->var, &info->modelist);
+	if (!fb_mode) {
+		DRM_DEBUG_KMS("Couldn't find var mode\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	mode_changed = !fb_mode_is_equal(info->mode, fb_mode);
+	info->mode = (struct fb_videomode *)fb_mode;
+
+	mode = drm_fbdev_get_drm_mode(fbdev);
+	if (!mode) {
+		DRM_DEBUG_KMS("Couldn't find the matching DRM mode\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	if (mode_changed) {
+		drm_client_buffer_rmfb(fbdev->buffer);
+		fbdev->curr_fb = 0;
+		ret = drm_client_buffer_addfb(fbdev->buffer, mode);
+		if (ret)
+			goto out_unlock;
+
+		fbdev->curr_fb = fbdev->buffer->fb_ids[0];
+		info->var.yoffset = 0;
+	}
+
+//	info->var.width = drm_mode->width_mm;
+//	info->var.height = drm_mode->height_mm;
+
+	/* Panning is only supported to do page flipping */
+	info->fix.ypanstep = info->var.yres;
+
+	ret = drm_client_display_commit_mode(fbdev->display, fbdev->curr_fb, mode);
+
+out_unlock:
+	mutex_unlock(&fbdev->lock);
+
+	return ret;
+}
+
+/*
+ * Do we need to support FB_VISUAL_PSEUDOCOLOR?
+
+static int drm_fbdev_fb_setcolreg(unsigned regno, unsigned red, unsigned green,
+		    unsigned blue, unsigned transp, struct fb_info *info)
+{
+
+}
+*/
+
+static int setcmap_pseudo_palette(struct fb_cmap *cmap, struct fb_info *info)
+{
+	u32 *palette = (u32 *)info->pseudo_palette;
+	int i;
+
+	if (cmap->start + cmap->len > 16)
+		return -EINVAL;
+
+	for (i = 0; i < cmap->len; ++i) {
+		u16 red = cmap->red[i];
+		u16 green = cmap->green[i];
+		u16 blue = cmap->blue[i];
+		u32 value;
+
+		red >>= 16 - info->var.red.length;
+		green >>= 16 - info->var.green.length;
+		blue >>= 16 - info->var.blue.length;
+		value = (red << info->var.red.offset) |
+			(green << info->var.green.offset) |
+			(blue << info->var.blue.offset);
+		if (info->var.transp.length > 0) {
+			u32 mask = (1 << info->var.transp.length) - 1;
+
+			mask <<= info->var.transp.offset;
+			value |= mask;
+		}
+		palette[cmap->start + i] = value;
+	}
+
+	return 0;
+}
+
+static int drm_fbdev_fb_setcmap(struct fb_cmap *cmap, struct fb_info *info)
+{
+	if (oops_in_progress)
+		return -EBUSY;
+
+	if (info->fix.visual == FB_VISUAL_TRUECOLOR)
+		return setcmap_pseudo_palette(cmap, info);
+
+	return -EINVAL;
+}
+
+static int drm_fbdev_fb_blank(int blank, struct fb_info *info)
+{
+	struct drm_fbdev *fbdev = info->par;
+	bool is_open;
+	int mode;
+
+	if (oops_in_progress)
+		return -EBUSY;
+
+	mutex_lock(&fbdev->lock);
+	is_open = fbdev->open_count;
+	mutex_unlock(&fbdev->lock);
+
+	if (!is_open)
+		return -EINVAL;
+
+	if (blank == FB_BLANK_UNBLANK)
+		mode = DRM_MODE_DPMS_ON;
+	else
+		mode = DRM_MODE_DPMS_OFF;
+
+	return drm_client_display_dpms(fbdev->display, mode);
+}
+
+static int
+drm_fbdev_fb_pan_display(struct fb_var_screeninfo *var, struct fb_info *info)
+{
+	struct drm_fbdev *fbdev = info->par;
+	struct drm_event *event;
+	unsigned int fb_idx;
+	int ret = 0;
+
+	mutex_lock(&fbdev->lock);
+
+	if (!fbdev->open_count)
+		goto out_unlock;
+
+	fb_idx = var->yoffset / info->var.yres;
+	if (fb_idx >= fbdev->buffer->num_fbs) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	/* Drain previous flip event if userspace didn't care */
+	if (fbdev->page_flip_sent) {
+		event = drm_client_read_event(fbdev->client, false);
+		if (!IS_ERR(event))
+			kfree(event);
+		fbdev->page_flip_sent = false;
+	}
+
+	if (fbdev->curr_fb == fbdev->buffer->fb_ids[fb_idx])
+		goto out_unlock;
+
+	fbdev->curr_fb = fbdev->buffer->fb_ids[fb_idx];
+	fbdev->defio_no_flushing = true;
+
+	ret = drm_client_display_page_flip(fbdev->display, fbdev->curr_fb, true);
+	if (ret)
+		goto out_unlock;
+
+	fbdev->page_flip_sent = true;
+
+out_unlock:
+	mutex_unlock(&fbdev->lock);
+
+	return ret;
+}
+
+static int drm_fbdev_fb_ioctl(struct fb_info *info, unsigned int cmd,
+			      unsigned long arg)
+{
+	struct drm_fbdev *fbdev = info->par;
+	struct drm_event *event;
+	bool page_flip_sent;
+	int ret = 0;
+
+	switch (cmd) {
+//	case FBIOGET_VBLANK:
+//		break;
+	case FBIO_WAITFORVSYNC:
+		mutex_lock(&fbdev->lock);
+		page_flip_sent = fbdev->page_flip_sent;
+		fbdev->page_flip_sent = false;
+		mutex_unlock(&fbdev->lock);
+
+		if (page_flip_sent) {
+			event = drm_client_read_event(fbdev->client, true);
+			if (IS_ERR(event))
+				ret = PTR_ERR(event);
+			else
+				kfree(event);
+		} else {
+			drm_client_display_wait_vblank(fbdev->display);
+		}
+
+		break;
+	default:
+		ret = -ENOTTY;
+	}
+
+	return ret;
+}
+
+static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
+{
+	struct drm_fbdev *fbdev = info->par;
+
+	return dma_buf_mmap(fbdev->buffer->dma_buf, vma, 0);
+}
+
+static void drm_fbdev_fb_destroy(struct fb_info *info)
+{
+	struct drm_fbdev *fbdev = info->par;
+
+	DRM_DEV_DEBUG_KMS(fbdev->client->dev->dev, "\n");
+	drm_client_display_free(fbdev->display);
+	drm_client_free(fbdev->client);
+	kfree(fbdev);
+}
+
+static struct fb_ops drm_fbdev_fb_ops = {
+	.owner		= THIS_MODULE,
+	.fb_open	= drm_fbdev_fb_open,
+	.fb_release	= drm_fbdev_fb_release,
+	.fb_read	= fb_sys_read,
+	.fb_write	= drm_fbdev_fb_write,
+	.fb_check_var	= drm_fbdev_fb_check_var,
+	.fb_set_par	= drm_fbdev_fb_set_par,
+//	.fb_setcolreg	= drm_fbdev_fb_setcolreg,
+	.fb_setcmap	= drm_fbdev_fb_setcmap,
+	.fb_blank	= drm_fbdev_fb_blank,
+	.fb_pan_display	= drm_fbdev_fb_pan_display,
+	.fb_fillrect	= drm_fbdev_fb_fillrect,
+	.fb_copyarea	= drm_fbdev_fb_copyarea,
+	.fb_imageblit	= drm_fbdev_fb_imageblit,
+	.fb_ioctl	= drm_fbdev_fb_ioctl,
+	.fb_mmap	= drm_fbdev_fb_mmap,
+	.fb_destroy	= drm_fbdev_fb_destroy,
+};
+
+static int drm_fbdev_register_framebuffer(struct drm_fbdev *fbdev)
+{
+	struct drm_client_display *display;
+	struct fb_info *info;
+	struct fb_ops *fbops;
+	u32 format;
+	int ret;
+
+	display = drm_client_display_get_first_enabled(fbdev->client, false);
+	if (IS_ERR_OR_NULL(display))
+		return PTR_ERR_OR_ZERO(display);
+
+	fbdev->display = display;
+
+	/*
+	 * fb_deferred_io_cleanup() clears &fbops->fb_mmap so a per instance
+	 * version is necessary. We do it for all users since we don't know
+	 * yet if the fb has a dirty callback.
+	 */
+	fbops = kzalloc(sizeof(*fbops), GFP_KERNEL);
+	if (!fbops) {
+		ret = -ENOMEM;
+		goto err_free;
+	}
+
+	*fbops = drm_fbdev_fb_ops;
+
+	info = framebuffer_alloc(0, fbdev->client->dev->dev);
+	if (!info) {
+		ret = -ENOMEM;
+		goto err_free;
+	}
+
+	ret = fb_alloc_cmap(&info->cmap, 256, 0);
+	if (ret)
+		goto err_release;
+
+	info->par = fbdev;
+	info->fbops = fbops;
+	INIT_LIST_HEAD(&info->modelist);
+	info->pseudo_palette = fbdev->pseudo_palette;
+
+	info->fix.type = FB_TYPE_PACKED_PIXELS;
+	info->fix.visual = FB_VISUAL_TRUECOLOR;
+	info->fix.ypanstep = info->var.yres;
+
+	strcpy(info->fix.id, "DRM emulated");
+
+	fbdev->info = info;
+	ret = drm_fbdev_sync_modes(fbdev, true);
+	if (ret < 0)
+		goto err_free_cmap;
+
+	info->var.bits_per_pixel = drm_client_display_preferred_depth(fbdev->display);
+	ret = drm_fbdev_var_to_format(&info->var, &format);
+	if (ret) {
+		DRM_WARN("Unsupported bpp, assuming x8r8g8b8 pixel format\n");
+		format = DRM_FORMAT_XRGB8888;
+	}
+	drm_fbdev_format_fill_var(format, &info->var);
+
+	info->var.xres_virtual = info->var.xres;
+	info->var.yres_virtual = info->var.yres;
+
+	info->var.yres_virtual *= CONFIG_DRM_FBDEV_OVERALLOC;
+	info->var.yres_virtual /= 100;
+
+	ret = register_framebuffer(info);
+	if (ret)
+		goto err_free_cmap;
+
+	dev_info(fbdev->client->dev->dev, "fb%d: %s frame buffer device\n",
+		 info->node, info->fix.id);
+
+	return 0;
+
+err_free_cmap:
+	fb_dealloc_cmap(&info->cmap);
+err_release:
+	framebuffer_release(info);
+err_free:
+	kfree(fbops);
+	fbdev->info = NULL;
+	drm_client_display_free(fbdev->display);
+	fbdev->display = NULL;
+
+	return ret;
+}
+
+static int drm_fbdev_client_hotplug(struct drm_client_dev *client)
+{
+	struct drm_fbdev *fbdev = client->private;
+	int ret;
+
+	if (!fbdev->info)
+		ret = drm_fbdev_register_framebuffer(fbdev);
+	else
+		ret = drm_fbdev_sync_modes(fbdev, false);
+
+	return ret;
+}
+
+static int drm_fbdev_client_new(struct drm_client_dev *client)
+{
+	struct drm_fbdev *fbdev;
+
+	fbdev = kzalloc(sizeof(*fbdev), GFP_KERNEL);
+	if (!fbdev)
+		return -ENOMEM;
+
+	mutex_init(&fbdev->lock);
+	spin_lock_init(&fbdev->dirty_lock);
+	INIT_WORK(&fbdev->dirty_work, drm_fbdev_dirty_work);
+
+	fbdev->client = client;
+	client->private = fbdev;
+
+	/*
+	 * vc4 isn't done with it's setup when drm_dev_register() is called.
+	 * It should have shouldn't it?
+	 * So to keep it from crashing defer setup to hotplug...
+	 */
+	if (client->dev->mode_config.max_width)
+		drm_fbdev_client_hotplug(client);
+
+	return 0;
+}
+
+static int drm_fbdev_client_remove(struct drm_client_dev *client)
+{
+	struct drm_fbdev *fbdev = client->private;
+
+	if (!fbdev->info) {
+		kfree(fbdev);
+		return 0;
+	}
+
+	unregister_framebuffer(fbdev->info);
+
+	/* drm_fbdev_fb_destroy() frees the client */
+	return 1;
+}
+
+static int drm_fbdev_client_lastclose(struct drm_client_dev *client)
+{
+	struct drm_fbdev *fbdev = client->private;
+	int ret = -ENOENT;
+
+	if (fbdev->info)
+		ret = fbdev->info->fbops->fb_set_par(fbdev->info);
+
+	return ret;
+}
+
+static const struct drm_client_funcs drm_fbdev_client_funcs = {
+	.name		= "drm_fbdev",
+	.new		= drm_fbdev_client_new,
+	.remove		= drm_fbdev_client_remove,
+	.lastclose	= drm_fbdev_client_lastclose,
+	.hotplug	= drm_fbdev_client_hotplug,
+};
+
+static int __init drm_fbdev_init(void)
+{
+	return drm_client_register(&drm_fbdev_client_funcs);
+}
+module_init(drm_fbdev_init);
+
+static void __exit drm_fbdev_exit(void)
+{
+	drm_client_unregister(&drm_fbdev_client_funcs);
+}
+module_exit(drm_fbdev_exit);
+
+MODULE_DESCRIPTION("DRM Generic fbdev emulation");
+MODULE_AUTHOR("Noralf Trønnes");
+MODULE_LICENSE("GPL");