[PATCH v5 2/6] hid: add framebuffer support to PicoLCD device

["Bruno Prémont" <bonbons@linux-vserver.org>]

Add framebuffer support to PicoLCD device with use of deferred-io.

Only changed areas of framebuffer get sent to device in order to
save USB bandwidth and especially resources on PicoLCD device or
allow higher refresh rate for a small area. Changed tiles are
determined while updating shadow framebuffer.

Changes since v4:
 - make backbuffer inconsistent with framebuffer to force refresh
   in picolcd_fb_reset (e.g. for reset_resume)
 - force picolcd_fb_update() to wait for urbs to get out of the queue
   when it sends more than 1/2 queue worth as a full display refresh
   fills the whole queue eventually causing queue overrun (and lost
   report) on a quick system
Changes since v3:
 - document fb_update_rate sysfs attribute
 - change fb_update_rate read behavior to match enum with selected
   in brackets presentation
Changes since v2:
 - add 8bit grayscale depth as near to no userspace app handles 1bit
 - properly send whole framebuffer on reset/init
 - drop inline keywords from non-stub functions
 - use device_{create,remove}_file instead of sysfs_{create,remove}_file

Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
---

Because on a quick system I get "output queue full" messages (and
incomplete update of device's display) when a full framebuffer has to
be transmitted back to PicoLCD device I have to wait on the queue to
get a few reports out.
Instead of duplicating "usbhid_wait_io()" I marked it with EXPORT_SYMBOL_GPL
so I can still build hid-picolcd as a module.



 Documentation/ABI/testing/sysfs-driver-hid-picolcd |   17 +
 drivers/hid/Kconfig                                |    7 +-
 drivers/hid/hid-picolcd.c                          |  570 +++++++++++++++++++-
 drivers/hid/usbhid/hid-core.c                      |    1 +
 4 files changed, 593 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-driver-hid-picolcd b/Documentation/ABI/testing/sysfs-driver-hid-picolcd
index 6fb4f21..14f52d7 100644
--- a/Documentation/ABI/testing/sysfs-driver-hid-picolcd
+++ b/Documentation/ABI/testing/sysfs-driver-hid-picolcd
@@ -15,3 +15,20 @@ Description:	Make it possible to switch the PicoLCD device between LCD
 		disconnected and reconnects after above delay (default value
 		is 5 seconds though this default should not be relied on).
 
+
+What:		/sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/<hid-bus>:<vendor-id>:<product-id>.<num>/fb_update_rate
+Date:		March 2010
+Contact:	Bruno Prémont <bonbons@linux-vserver.org>
+Description:	Make it possible to adjust defio refresh rate.
+
+		Reading: returns list of available refresh rates (expressed in Hz),
+		the active refresh rate being enclosed in brackets ('[' and ']')
+
+		Writing: accepts new refresh rate expressed in integer Hz
+		within permitted rates.
+
+		Note: As device can barely do 2 complete refreshes a second
+		it only makes sense to adjust this value if only one or two
+		tiles get changed and it's not appropriate to expect the application
+		to flush it's tiny changes explicitely at higher than default rate.
+
diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 138ba6a..a813ea9 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -265,6 +265,11 @@ config HID_PETALYNX
 config HID_PICOLCD
 	tristate "PicoLCD (graphic version)"
 	depends on USB_HID
+	select FB_DEFERRED_IO if FB
+	select FB_SYS_FILLRECT if FB
+	select FB_SYS_COPYAREA if FB
+	select FB_SYS_IMAGEBLIT if FB
+	select FB_SYS_FOPS if FB
 	---help---
 	  This provides support for Minibox PicoLCD devices, currently
 	  only the graphical ones are supported.
@@ -272,8 +277,8 @@ config HID_PICOLCD
 	  This includes support for the following device features:
 	  - Keypad
 	  - Switching between Firmware and Flash mode
-	  Features that are not (yet) supported:
 	  - Framebuffer for monochrome 256x64 display
+	  Features that are not (yet) supported:
 	  - Backlight control
 	  - Contrast control
 	  - IR
diff --git a/drivers/hid/hid-picolcd.c b/drivers/hid/hid-picolcd.c
index 28f8ea0..efc4bc8 100644
--- a/drivers/hid/hid-picolcd.c
+++ b/drivers/hid/hid-picolcd.c
@@ -24,6 +24,9 @@
 #include "usbhid/usbhid.h"
 #include <linux/usb.h>
 
+#include <linux/fb.h>
+#include <linux/vmalloc.h>
+
 #include <linux/seq_file.h>
 #include <linux/debugfs.h>
 
@@ -69,6 +72,59 @@
 #define REPORT_HOOK_VERSION    0xf7 /* LCD: IN[2], OUT[1]   */
 #define REPORT_EXIT_FLASHER    0xff /*                      Bootloader: OUT[2]         */
 
+#if defined(CONFIG_FB) || defined(CONFIG_FB_MODULE)
+/* Framebuffer
+ *
+ * The PicoLCD use a Topway LCD module of 256x64 pixel
+ * This display area is tiled over 4 controllers with 8 tiles
+ * each. Each tile has 8x64 pixel, each data byte representing
+ * a 1-bit wide vertical line of the tile.
+ *
+ * The display can be updated at a tile granularity.
+ *
+ *       Chip 1           Chip 2           Chip 3           Chip 4
+ * +----------------+----------------+----------------+----------------+
+ * |     Tile 1     |     Tile 1     |     Tile 1     |     Tile 1     |
+ * +----------------+----------------+----------------+----------------+
+ * |     Tile 2     |     Tile 2     |     Tile 2     |     Tile 2     |
+ * +----------------+----------------+----------------+----------------+
+ *                                  ...
+ * +----------------+----------------+----------------+----------------+
+ * |     Tile 8     |     Tile 8     |     Tile 8     |     Tile 8     |
+ * +----------------+----------------+----------------+----------------+
+ */
+#define PICOLCDFB_NAME "picolcdfb"
+#define PICOLCDFB_WIDTH (256)
+#define PICOLCDFB_HEIGHT (64)
+#define PICOLCDFB_SIZE (PICOLCDFB_WIDTH * PICOLCDFB_HEIGHT / 8)
+
+#define PICOLCDFB_UPDATE_RATE_LIMIT   10
+#define PICOLCDFB_UPDATE_RATE_DEFAULT  2
+
+/* Framebuffer visual structures */
+static const struct fb_fix_screeninfo picolcdfb_fix = {
+	.id          = PICOLCDFB_NAME,
+	.type        = FB_TYPE_PACKED_PIXELS,
+	.visual      = FB_VISUAL_MONO01,
+	.xpanstep    = 0,
+	.ypanstep    = 0,
+	.ywrapstep   = 0,
+	.line_length = PICOLCDFB_WIDTH / 8,
+	.accel       = FB_ACCEL_NONE,
+};
+
+static const struct fb_var_screeninfo picolcdfb_var = {
+	.xres           = PICOLCDFB_WIDTH,
+	.yres           = PICOLCDFB_HEIGHT,
+	.xres_virtual   = PICOLCDFB_WIDTH,
+	.yres_virtual   = PICOLCDFB_HEIGHT,
+	.width          = 103,
+	.height         = 26,
+	.bits_per_pixel = 1,
+	.grayscale      = 1,
+};
+#endif /* CONFIG_FB */
+
 /* Input device
  *
  * The PicoLCD has an IR receiver header, a built-in keypad with 5 keys
@@ -118,6 +174,16 @@ struct picolcd_data {
 	struct input_dev *input_cir;
 	unsigned short keycode[PICOLCD_KEYS];
 
+#if defined(CONFIG_FB) || defined(CONFIG_FB_MODULE)
+	/* Framebuffer stuff */
+	u8 fb_update_rate;
+	u8 fb_bpp;
+	u8 *fb_vbitmap;		/* local copy of what was sent to PicoLCD */
+	u8 *fb_bitmap;		/* framebuffer */
+	struct fb_info *fb_info;
+	struct fb_deferred_io fb_defio;
+#endif /* CONFIG_FB */
+
 	/* Housekeeping stuff */
 	spinlock_t lock;
 	struct mutex mutex;
@@ -125,6 +191,7 @@ struct picolcd_data {
 	int status;
 #define PICOLCD_BOOTLOADER 1
 #define PICOLCD_FAILED 2
+#define PICOLCD_READY_FB 4
 };
 
 
@@ -197,6 +264,486 @@ static struct picolcd_pending *picolcd_send_and_wait(struct hid_device *hdev,
 	return work;
 }
 
+#if defined(CONFIG_FB) || defined(CONFIG_FB_MODULE)
+/* Send a given tile to PicoLCD */
+static int picolcd_fb_send_tile(struct hid_device *hdev, int chip, int tile)
+{
+	struct picolcd_data *data = hid_get_drvdata(hdev);
+	struct hid_report *report1 = picolcd_out_report(REPORT_LCD_CMD_DATA, hdev);
+	struct hid_report *report2 = picolcd_out_report(REPORT_LCD_DATA, hdev);
+	unsigned long flags;
+	u8 *tdata;
+	int i;
+
+	if (!report1 || report1->maxfield != 1 || !report2 || report2->maxfield != 1)
+		return -ENODEV;
+
+	spin_lock_irqsave(&data->lock, flags);
+	hid_set_field(report1->field[0],  0, chip << 2);
+	hid_set_field(report1->field[0],  1, 0x02);
+	hid_set_field(report1->field[0],  2, 0x00);
+	hid_set_field(report1->field[0],  3, 0x00);
+	hid_set_field(report1->field[0],  4, 0xb8 | tile);
+	hid_set_field(report1->field[0],  5, 0x00);
+	hid_set_field(report1->field[0],  6, 0x00);
+	hid_set_field(report1->field[0],  7, 0x40);
+	hid_set_field(report1->field[0],  8, 0x00);
+	hid_set_field(report1->field[0],  9, 0x00);
+	hid_set_field(report1->field[0], 10,   32);
+
+	hid_set_field(report2->field[0],  0, (chip << 2) | 0x01);
+	hid_set_field(report2->field[0],  1, 0x00);
+	hid_set_field(report2->field[0],  2, 0x00);
+	hid_set_field(report2->field[0],  3,   32);
+
+	tdata = data->fb_vbitmap + (tile * 4 + chip) * 64;
+	for (i = 0; i < 64; i++)
+		if (i < 32)
+			hid_set_field(report1->field[0], 11 + i, tdata[i]);
+		else
+			hid_set_field(report2->field[0], 4 + i - 32, tdata[i]);
+
+	usbhid_submit_report(data->hdev, report1, USB_DIR_OUT);
+	usbhid_submit_report(data->hdev, report2, USB_DIR_OUT);
+	spin_unlock_irqrestore(&data->lock, flags);
+	return 0;
+}
+
+/* Translate a single tile*/
+static int picolcd_fb_update_tile(u8 *vbitmap, const u8 *bitmap, int bpp,
+		int chip, int tile)
+{
+	int i, b, changed = 0;
+	u8 tdata[64];
+	u8 *vdata = vbitmap + (tile * 4 + chip) * 64;
+
+	if (bpp == 1) {
+		for (b = 7; b >= 0; b--) {
+			const u8 *bdata = bitmap + tile * 256 + chip * 8 + b * 32;
+			for (i = 0; i < 64; i++) {
+				tdata[i] <<= 1;
+				tdata[i] |= (bdata[i/8] >> (7 - i % 8)) & 0x01;
+			}
+		}
+	} else if (bpp == 8) {
+		for (b = 7; b >= 0; b--) {
+			const u8 *bdata = bitmap + (tile * 256 + chip * 8 + b * 32) * 8;
+			for (i = 0; i < 64; i++) {
+				tdata[i] <<= 1;
+				tdata[i] |= (bdata[i] & 0x80) ? 0x01 : 0x00;
+			}
+		}
+	} else {
+		/* Oops, we should never get here! */
+		WARN_ON(1);
+		return 0;
+	}
+
+	for (i = 0; i < 64; i++)
+		if (tdata[i] != vdata[i]) {
+			changed = 1;
+			vdata[i] = tdata[i];
+		}
+	return changed;
+}
+
+/* Reconfigure LCD display */
+static int picolcd_fb_reset(struct picolcd_data *data, int clear)
+{
+	struct hid_report *report = picolcd_out_report(REPORT_LCD_CMD, data->hdev);
+	int i, j;
+	unsigned long flags;
+	static const u8 mapcmd[8] = { 0x00, 0x02, 0x00, 0x64, 0x3f, 0x00, 0x64, 0xc0 };
+
+	if (!report || report->maxfield != 1)
+		return -ENODEV;
+
+	spin_lock_irqsave(&data->lock, flags);
+	for (i = 0; i < 4; i++) {
+		for (j = 0; j < report->field[0]->maxusage; j++)
+			if (j == 0)
+				hid_set_field(report->field[0], j, i << 2);
+			else if (j < sizeof(mapcmd))
+				hid_set_field(report->field[0], j, mapcmd[j]);
+			else
+				hid_set_field(report->field[0], j, 0);
+		usbhid_submit_report(data->hdev, report, USB_DIR_OUT);
+	}
+
+	data->status |= PICOLCD_READY_FB;
+	spin_unlock_irqrestore(&data->lock, flags);
+
+	if (data->fb_bitmap) {
+		if (clear) {
+			memset(data->fb_vbitmap, 0xff, PICOLCDFB_SIZE);
+			memset(data->fb_bitmap, 0, PICOLCDFB_SIZE*data->fb_bpp);
+		} else {
+			/* invert 1 byte in each tile to force resend */
+			for (i = 0; i < PICOLCDFB_SIZE; i+=64)
+				data->fb_vbitmap[i] = ~data->fb_vbitmap[i];
+		}
+	}
+
+	/* schedule first output of framebuffer */
+	if (data->fb_info)
+		schedule_delayed_work(&data->fb_info->deferred_work, 0);
+
+	return 0;
+}
+
+/* Update fb_vbitmap from the screen_base and send changed tiles to device */
+static void picolcd_fb_update(struct picolcd_data *data)
+{
+	int chip, tile, n;
+	unsigned long flags;
+
+	spin_lock_irqsave(&data->lock, flags);
+	if (!(data->status & PICOLCD_READY_FB)) {
+		spin_unlock_irqrestore(&data->lock, flags);
+		picolcd_fb_reset(data, 0);
+	} else {
+		spin_unlock_irqrestore(&data->lock, flags);
+	}
+
+	/*
+	 * Translate the framebuffer into the format needed by the PicoLCD.
+	 * See display layout above.
+	 * Do this one tile after the other and push those tiles that changed.
+	 *
+	 * Wait for our IO to complete as otherwise we might flood the queue!
+	 */
+	n = 0;
+	for (chip = 0; chip < 4; chip++)
+		for (tile = 0; tile < 8; tile++)
+			if (picolcd_fb_update_tile(data->fb_vbitmap,
+					data->fb_bitmap, data->fb_bpp, chip, tile)) {
+				n += 2;
+				if (n >= HID_OUTPUT_FIFO_SIZE / 2) {
+					usbhid_wait_io(data->hdev);
+					n = 0;
+				}
+				picolcd_fb_send_tile(data->hdev, chip, tile);
+			}
+	if (n)
+		usbhid_wait_io(data->hdev);
+}
+
+/* Stub to call the system default and update the image on the picoLCD */
+static void picolcd_fb_fillrect(struct fb_info *info,
+		const struct fb_fillrect *rect)
+{
+	if (!info->par)
+		return;
+	sys_fillrect(info, rect);
+
+	schedule_delayed_work(&info->deferred_work, 0);
+}
+
+/* Stub to call the system default and update the image on the picoLCD */
+static void picolcd_fb_copyarea(struct fb_info *info,
+		const struct fb_copyarea *area)
+{
+	if (!info->par)
+		return;
+	sys_copyarea(info, area);
+
+	schedule_delayed_work(&info->deferred_work, 0);
+}
+
+/* Stub to call the system default and update the image on the picoLCD */
+static void picolcd_fb_imageblit(struct fb_info *info, const struct fb_image *image)
+{
+	if (!info->par)
+		return;
+	sys_imageblit(info, image);
+
+	schedule_delayed_work(&info->deferred_work, 0);
+}
+
+/*
+ * this is the slow path from userspace. they can seek and write to
+ * the fb. it's inefficient to do anything less than a full screen draw
+ */
+static ssize_t picolcd_fb_write(struct fb_info *info, const char __user *buf,
+		size_t count, loff_t *ppos)
+{
+	ssize_t ret;
+	if (!info->par)
+		return -ENODEV;
+	ret = fb_sys_write(info, buf, count, ppos);
+	if (ret >= 0)
+		schedule_delayed_work(&info->deferred_work, 0);
+	return ret;
+}
+
+static int picolcd_fb_blank(int blank, struct fb_info *info)
+{
+	if (!info->par)
+		return -ENODEV;
+	/* We let fb notification do this for us via lcd/backlight device */
+	return 0;
+}
+
+static void picolcd_fb_destroy(struct fb_info *info)
+{
+	struct picolcd_data *data = info->par;
+	info->par = NULL;
+	if (data)
+		data->fb_info = NULL;
+	fb_deferred_io_cleanup(info);
+	framebuffer_release(info);
+}
+
+static int picolcd_fb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
+{
+	__u32 bpp      = var->bits_per_pixel;
+	__u32 activate = var->activate;
+
+	/* only allow 1/8 bit depth (8-bit is grayscale) */
+	*var = picolcdfb_var;
+	var->activate = activate;
+	if (bpp >= 8)
+		var->bits_per_pixel = 8;
+	else
+		var->bits_per_pixel = 1;
+	return 0;
+}
+
+static int picolcd_set_par(struct fb_info *info)
+{
+	struct picolcd_data *data = info->par;
+	u8 *o_fb, *n_fb;
+	if (info->var.bits_per_pixel == data->fb_bpp)
+		return 0;
+	/* switch between 1/8 bit depths */
+	if (info->var.bits_per_pixel != 1 && info->var.bits_per_pixel != 8)
+		return -EINVAL;
+
+	o_fb = data->fb_bitmap;
+	n_fb = vmalloc(PICOLCDFB_SIZE*info->var.bits_per_pixel);
+	if (!n_fb)
+		return -ENOMEM;
+
+	fb_deferred_io_cleanup(info);
+	/* translate FB content to new bits-per-pixel */
+	if (info->var.bits_per_pixel == 1) {
+		int i, b;
+		for (i = 0; i < PICOLCDFB_SIZE; i++) {
+			u8 p = 0;
+			for (b = 0; b < 8; b++) {
+				p <<= 1;
+				p |= o_fb[i*8+b] ? 0x01 : 0x00;
+			}
+		}
+		info->fix.visual = FB_VISUAL_MONO01;
+		info->fix.line_length = PICOLCDFB_WIDTH / 8;
+	} else {
+		int i;
+		for (i = 0; i < PICOLCDFB_SIZE * 8; i++)
+			n_fb[i] = o_fb[i/8] & (0x01 << (7 - i % 8)) ? 0xff : 0x00;
+		info->fix.visual = FB_VISUAL_TRUECOLOR;
+		info->fix.line_length = PICOLCDFB_WIDTH;
+	}
+
+	data->fb_bitmap   = n_fb;
+	data->fb_bpp      = info->var.bits_per_pixel;
+	info->screen_base = (char __force __iomem *)n_fb;
+	info->fix.smem_start = (unsigned long)n_fb;
+	info->fix.smem_len   = PICOLCDFB_SIZE*data->fb_bpp;
+	fb_deferred_io_init(info);
+	vfree(o_fb);
+	return 0;
+}
+
+/* Note this can't be const because of struct fb_info definition */
+static struct fb_ops picolcdfb_ops = {
+	.owner        = THIS_MODULE,
+	.fb_destroy   = picolcd_fb_destroy,
+	.fb_read      = fb_sys_read,
+	.fb_write     = picolcd_fb_write,
+	.fb_blank     = picolcd_fb_blank,
+	.fb_fillrect  = picolcd_fb_fillrect,
+	.fb_copyarea  = picolcd_fb_copyarea,
+	.fb_imageblit = picolcd_fb_imageblit,
+	.fb_check_var = picolcd_fb_check_var,
+	.fb_set_par   = picolcd_set_par,
+};
+
+
+/* Callback from deferred IO workqueue */
+static void picolcd_fb_deferred_io(struct fb_info *info, struct list_head *pagelist)
+{
+	picolcd_fb_update(info->par);
+}
+
+static const struct fb_deferred_io picolcd_fb_defio = {
+	.delay = HZ / PICOLCDFB_UPDATE_RATE_DEFAULT,
+	.deferred_io = picolcd_fb_deferred_io,
+};
+
+
+/*
+ * The "fb_update_rate" sysfs attribute
+ */
+static ssize_t picolcd_fb_update_rate_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct picolcd_data *data = dev_get_drvdata(dev);
+	unsigned i, fb_update_rate = data->fb_update_rate;
+	size_t ret = 0;
+
+	for (i = 1; i <= PICOLCDFB_UPDATE_RATE_LIMIT; i++)
+		if (ret >= PAGE_SIZE)
+			break;
+		else if (i == fb_update_rate)
+			ret += snprintf(buf+ret, PAGE_SIZE-ret, "[%u] ", i);
+		else
+			ret += snprintf(buf+ret, PAGE_SIZE-ret, "%u ", i);
+	if (ret > 0)
+		buf[min(ret, (size_t)PAGE_SIZE)-1] = '\n';
+	return ret;
+}
+
+static ssize_t picolcd_fb_update_rate_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct picolcd_data *data = dev_get_drvdata(dev);
+	int i;
+	unsigned u;
+
+	if (count < 1 || count > 10)
+		return -EINVAL;
+
+	i = sscanf(buf, "%u", &u);
+	if (i != 1)
+		return -EINVAL;
+
+	if (u > PICOLCDFB_UPDATE_RATE_LIMIT)
+		return -ERANGE;
+	else if (u == 0)
+		u = PICOLCDFB_UPDATE_RATE_DEFAULT;
+
+	data->fb_update_rate = u;
+	data->fb_defio.delay = HZ / data->fb_update_rate;
+	return count;
+}
+
+static DEVICE_ATTR(fb_update_rate, 0666, picolcd_fb_update_rate_show,
+		picolcd_fb_update_rate_store);
+
+/* initialize Framebuffer device */
+static int picolcd_init_framebuffer(struct picolcd_data *data)
+{
+	struct device *dev = &data->hdev->dev;
+	struct fb_info *info = NULL;
+	int error = -ENOMEM;
+	u8 *fb_vbitmap = NULL;
+	u8 *fb_bitmap  = NULL;
+
+	fb_bitmap = vmalloc(PICOLCDFB_SIZE*picolcdfb_var.bits_per_pixel);
+	if (fb_bitmap == NULL) {
+		dev_err(dev, "can't get a free page for framebuffer\n");
+		goto err_nomem;
+	}
+
+	fb_vbitmap = kmalloc(PICOLCDFB_SIZE, GFP_KERNEL);
+	if (fb_vbitmap == NULL) {
+		dev_err(dev, "can't alloc vbitmap image buffer\n");
+		goto err_nomem;
+	}
+
+	data->fb_update_rate = PICOLCDFB_UPDATE_RATE_DEFAULT;
+	data->fb_defio = picolcd_fb_defio;
+	info = framebuffer_alloc(0, dev);
+	if (info == NULL) {
+		dev_err(dev, "failed to allocate a framebuffer\n");
+		goto err_nomem;
+	}
+
+	info->fbdefio = &data->fb_defio;
+	info->screen_base = (char __force __iomem *)fb_bitmap;
+	info->fbops = &picolcdfb_ops;
+	info->var = picolcdfb_var;
+	info->fix = picolcdfb_fix;
+	info->fix.smem_len   = PICOLCDFB_SIZE;
+	info->fix.smem_start = (unsigned long)fb_bitmap;
+	info->par = data;
+	info->flags = FBINFO_FLAG_DEFAULT;
+
+	data->fb_vbitmap = fb_vbitmap;
+	data->fb_bitmap  = fb_bitmap;
+	data->fb_bpp     = picolcdfb_var.bits_per_pixel;
+	error = picolcd_fb_reset(data, 1);
+	if (error) {
+		dev_err(dev, "failed to configure display\n");
+		goto err_cleanup;
+	}
+	error = device_create_file(dev, &dev_attr_fb_update_rate);
+	if (error) {
+		dev_err(dev, "failed to create sysfs attributes\n");
+		goto err_cleanup;
+	}
+	data->fb_info    = info;
+	error = register_framebuffer(info);
+	if (error) {
+		dev_err(dev, "failed to register framebuffer\n");
+		goto err_sysfs;
+	}
+	fb_deferred_io_init(info);
+	/* schedule first output of framebuffer */
+	schedule_delayed_work(&info->deferred_work, 0);
+	return 0;
+
+err_sysfs:
+	device_remove_file(dev, &dev_attr_fb_update_rate);
+err_cleanup:
+	data->fb_vbitmap = NULL;
+	data->fb_bitmap  = NULL;
+	data->fb_bpp     = 0;
+	data->fb_info    = NULL;
+
+err_nomem:
+	framebuffer_release(info);
+	vfree(fb_bitmap);
+	kfree(fb_vbitmap);
+	return error;
+}
+
+static void picolcd_exit_framebuffer(struct picolcd_data *data)
+{
+	struct fb_info *info = data->fb_info;
+	u8 *fb_vbitmap = data->fb_vbitmap;
+	u8 *fb_bitmap  = data->fb_bitmap;
+
+	if (!info)
+		return;
+
+	data->fb_vbitmap = NULL;
+	data->fb_bitmap  = NULL;
+	data->fb_bpp     = 0;
+	data->fb_info    = NULL;
+	device_remove_file(&data->hdev->dev, &dev_attr_fb_update_rate);
+	fb_deferred_io_cleanup(info);
+	unregister_framebuffer(info);
+	vfree(fb_bitmap);
+	kfree(fb_vbitmap);
+}
+
+
+#else
+static inline int picolcd_fb_reset(struct picolcd_data *data, int clear)
+{
+	return 0;
+}
+static inline int picolcd_init_framebuffer(struct picolcd_data *data)
+{
+	return 0;
+}
+static void picolcd_exit_framebuffer(struct picolcd_data *data)
+{
+}
+#endif /* CONFIG_FB */
+
 /*
  * input class device
  */
@@ -314,6 +861,7 @@ static int picolcd_reset(struct hid_device *hdev)
 	struct picolcd_data *data = hid_get_drvdata(hdev);
 	struct hid_report *report = picolcd_out_report(REPORT_RESET, hdev);
 	unsigned long flags;
+	int error;
 
 	if (!data || !report || report->maxfield != 1)
 		return -ENODEV;
@@ -327,7 +875,16 @@ static int picolcd_reset(struct hid_device *hdev)
 	usbhid_submit_report(hdev, report, USB_DIR_OUT);
 	spin_unlock_irqrestore(&data->lock, flags);
 
-	return picolcd_check_version(hdev);
+	error = picolcd_check_version(hdev);
+	if (error)
+		return error;
+
+#if defined(CONFIG_FB) || defined(CONFIG_FB_MODULE)
+	if (data->fb_info)
+		schedule_delayed_work(&data->fb_info->deferred_work, 0);
+#endif /* CONFIG_FB */
+
+	return 0;
 }
 
 /*
@@ -931,6 +1488,9 @@ static int picolcd_reset_resume(struct hid_device *hdev)
 	ret = picolcd_reset(hdev);
 	if (ret)
 		dbg_hid(PICOLCD_NAME " resetting our device failed: %d\n", ret);
+	ret = picolcd_fb_reset(hid_get_drvdata(hdev), 0);
+	if (ret)
+		dbg_hid(PICOLCD_NAME " restoring framebuffer content failed: %d\n", ret);
 	return 0;
 }
 #endif
@@ -1027,6 +1587,11 @@ static int picolcd_probe_lcd(struct hid_device *hdev, struct picolcd_data *data)
 	if (error)
 		goto err;
 
+	/* Set up the framebuffer device */
+	error = picolcd_init_framebuffer(data);
+	if (error)
+		goto err;
+
 #ifdef CONFIG_DEBUG_FS
 	report = picolcd_out_report(REPORT_READ_MEMORY, hdev);
 	if (report && report->maxfield == 1 && report->field[0]->report_size == 8)
@@ -1036,6 +1601,7 @@ static int picolcd_probe_lcd(struct hid_device *hdev, struct picolcd_data *data)
 #endif
 	return 0;
 err:
+	picolcd_exit_framebuffer(data);
 	picolcd_exit_cir(data);
 	picolcd_exit_keys(data);
 	return error;
@@ -1165,6 +1731,8 @@ static void picolcd_remove(struct hid_device *hdev)
 		complete(&data->pending->ready);
 	spin_unlock_irqrestore(&data->lock, flags);
 
+	/* Clean up the framebuffer */
+	picolcd_exit_framebuffer(data);
 	/* Cleanup input */
 	picolcd_exit_cir(data);
 	picolcd_exit_keys(data);
diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
index 39fe2e8..9acf573 100644
--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c
@@ -623,6 +623,7 @@ int usbhid_wait_io(struct hid_device *hid)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(usbhid_wait_io);
 
 static int hid_set_idle(struct usb_device *dev, int ifnum, int report, int idle)
 {
-- 
1.6.4.4