xen pvfb: Para-virtual framebuffer, keyboard and pointer driver

This is a pair of Xen para-virtual frontend device drivers:
drivers/video/xen-fbfront.c provides a framebuffer, and
drivers/input/xen-kbdfront provides keyboard and mouse.

The backends run in dom0 user space.

The two drivers are not in two separate patches, because the
intermediate step (one driver, not the other) is somewhat problematic:
the backend in dom0 needs both drivers, and will refuse to complete
device initialization unless they're both present.

Signed-off-by: Markus Armbruster <armbru@redhat.com>

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

6 files changed, 916 insertions, 0 deletions

diff --git a/drivers/input/Kconfig b/drivers/input/Kconfig
index 9dea14db724c..5f9d860925a1 100644
--- a/drivers/input/Kconfig
+++ b/drivers/input/Kconfig
@@ -149,6 +149,15 @@ config INPUT_APMPOWER
           To compile this driver as a module, choose M here: the
           module will be called apm-power.
 
+config XEN_KBDDEV_FRONTEND
+        tristate "Xen virtual keyboard and mouse support"
+        depends on XEN_FBDEV_FRONTEND
+        default y
+        help
+          This driver implements the front-end of the Xen virtual
+          keyboard and mouse device driver.  It communicates with a back-end
+          in another domain.
+
 comment "Input Device Drivers"
 
 source "drivers/input/keyboard/Kconfig"
diff --git a/drivers/input/Makefile b/drivers/input/Makefile
index 2ae87b19caa8..98c4f9a77876 100644
--- a/drivers/input/Makefile
+++ b/drivers/input/Makefile
@@ -23,3 +23,5 @@ obj-$(CONFIG_INPUT_TOUCHSCREEN)	+= touchscreen/
 obj-$(CONFIG_INPUT_MISC)        += misc/
 
 obj-$(CONFIG_INPUT_APMPOWER)    += apm-power.o
+
+obj-$(CONFIG_XEN_KBDDEV_FRONTEND)       += xen-kbdfront.o
diff --git a/drivers/input/xen-kbdfront.c b/drivers/input/xen-kbdfront.c
new file mode 100644
index 000000000000..0f47f4697cdf
--- /dev/null
+++ b/drivers/input/xen-kbdfront.c
@@ -0,0 +1,340 @@
+/*
+ * Xen para-virtual input device
+ *
+ * Copyright (C) 2005 Anthony Liguori <aliguori@us.ibm.com>
+ * Copyright (C) 2006-2008 Red Hat, Inc., Markus Armbruster <armbru@redhat.com>
+ *
+ *  Based on linux/drivers/input/mouse/sermouse.c
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License. See the file COPYING in the main directory of this archive for
+ *  more details.
+ */
+
+/*
+ * TODO:
+ *
+ * Switch to grant tables together with xen-fbfront.c.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/input.h>
+#include <asm/xen/hypervisor.h>
+#include <xen/events.h>
+#include <xen/page.h>
+#include <xen/interface/io/fbif.h>
+#include <xen/interface/io/kbdif.h>
+#include <xen/xenbus.h>
+
+struct xenkbd_info {
+        struct input_dev *kbd;
+        struct input_dev *ptr;
+        struct xenkbd_page *page;
+        int irq;
+        struct xenbus_device *xbdev;
+        char phys[32];
+};
+
+static int xenkbd_remove(struct xenbus_device *);
+static int xenkbd_connect_backend(struct xenbus_device *, struct xenkbd_info *);
+static void xenkbd_disconnect_backend(struct xenkbd_info *);
+
+/*
+ * Note: if you need to send out events, see xenfb_do_update() for how
+ * to do that.
+ */
+
+static irqreturn_t input_handler(int rq, void *dev_id)
+{
+        struct xenkbd_info *info = dev_id;
+        struct xenkbd_page *page = info->page;
+        __u32 cons, prod;
+
+        prod = page->in_prod;
+        if (prod == page->in_cons)
+                return IRQ_HANDLED;
+        rmb();                  /* ensure we see ring contents up to prod */
+        for (cons = page->in_cons; cons != prod; cons++) {
+                union xenkbd_in_event *event;
+                struct input_dev *dev;
+                event = &XENKBD_IN_RING_REF(page, cons);
+
+                dev = info->ptr;
+                switch (event->type) {
+                case XENKBD_TYPE_MOTION:
+                        input_report_rel(dev, REL_X, event->motion.rel_x);
+                        input_report_rel(dev, REL_Y, event->motion.rel_y);
+                        break;
+                case XENKBD_TYPE_KEY:
+                        dev = NULL;
+                        if (test_bit(event->key.keycode, info->kbd->keybit))
+                                dev = info->kbd;
+                        if (test_bit(event->key.keycode, info->ptr->keybit))
+                                dev = info->ptr;
+                        if (dev)
+                                input_report_key(dev, event->key.keycode,
+                                                 event->key.pressed);
+                        else
+                                printk(KERN_WARNING
+                                       "xenkbd: unhandled keycode 0x%x\n",
+                                       event->key.keycode);
+                        break;
+                case XENKBD_TYPE_POS:
+                        input_report_abs(dev, ABS_X, event->pos.abs_x);
+                        input_report_abs(dev, ABS_Y, event->pos.abs_y);
+                        break;
+                }
+                if (dev)
+                        input_sync(dev);
+        }
+        mb();                   /* ensure we got ring contents */
+        page->in_cons = cons;
+        notify_remote_via_irq(info->irq);
+
+        return IRQ_HANDLED;
+}
+
+static int __devinit xenkbd_probe(struct xenbus_device *dev,
+                                  const struct xenbus_device_id *id)
+{
+        int ret, i;
+        struct xenkbd_info *info;
+        struct input_dev *kbd, *ptr;
+
+        info = kzalloc(sizeof(*info), GFP_KERNEL);
+        if (!info) {
+                xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
+                return -ENOMEM;
+        }
+        dev->dev.driver_data = info;
+        info->xbdev = dev;
+        info->irq = -1;
+        snprintf(info->phys, sizeof(info->phys), "xenbus/%s", dev->nodename);
+
+        info->page = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+        if (!info->page)
+                goto error_nomem;
+
+        /* keyboard */
+        kbd = input_allocate_device();
+        if (!kbd)
+                goto error_nomem;
+        kbd->name = "Xen Virtual Keyboard";
+        kbd->phys = info->phys;
+        kbd->id.bustype = BUS_PCI;
+        kbd->id.vendor = 0x5853;
+        kbd->id.product = 0xffff;
+        kbd->evbit[0] = BIT(EV_KEY);
+        for (i = KEY_ESC; i < KEY_UNKNOWN; i++)
+                set_bit(i, kbd->keybit);
+        for (i = KEY_OK; i < KEY_MAX; i++)
+                set_bit(i, kbd->keybit);
+
+        ret = input_register_device(kbd);
+        if (ret) {
+                input_free_device(kbd);
+                xenbus_dev_fatal(dev, ret, "input_register_device(kbd)");
+                goto error;
+        }
+        info->kbd = kbd;
+
+        /* pointing device */
+        ptr = input_allocate_device();
+        if (!ptr)
+                goto error_nomem;
+        ptr->name = "Xen Virtual Pointer";
+        ptr->phys = info->phys;
+        ptr->id.bustype = BUS_PCI;
+        ptr->id.vendor = 0x5853;
+        ptr->id.product = 0xfffe;
+        ptr->evbit[0] = BIT(EV_KEY) | BIT(EV_REL) | BIT(EV_ABS);
+        for (i = BTN_LEFT; i <= BTN_TASK; i++)
+                set_bit(i, ptr->keybit);
+        ptr->relbit[0] = BIT(REL_X) | BIT(REL_Y);
+        input_set_abs_params(ptr, ABS_X, 0, XENFB_WIDTH, 0, 0);
+        input_set_abs_params(ptr, ABS_Y, 0, XENFB_HEIGHT, 0, 0);
+
+        ret = input_register_device(ptr);
+        if (ret) {
+                input_free_device(ptr);
+                xenbus_dev_fatal(dev, ret, "input_register_device(ptr)");
+                goto error;
+        }
+        info->ptr = ptr;
+
+        ret = xenkbd_connect_backend(dev, info);
+        if (ret < 0)
+                goto error;
+
+        return 0;
+
+ error_nomem:
+        ret = -ENOMEM;
+        xenbus_dev_fatal(dev, ret, "allocating device memory");
+ error:
+        xenkbd_remove(dev);
+        return ret;
+}
+
+static int xenkbd_resume(struct xenbus_device *dev)
+{
+        struct xenkbd_info *info = dev->dev.driver_data;
+
+        xenkbd_disconnect_backend(info);
+        memset(info->page, 0, PAGE_SIZE);
+        return xenkbd_connect_backend(dev, info);
+}
+
+static int xenkbd_remove(struct xenbus_device *dev)
+{
+        struct xenkbd_info *info = dev->dev.driver_data;
+
+        xenkbd_disconnect_backend(info);
+        if (info->kbd)
+                input_unregister_device(info->kbd);
+        if (info->ptr)
+                input_unregister_device(info->ptr);
+        free_page((unsigned long)info->page);
+        kfree(info);
+        return 0;
+}
+
+static int xenkbd_connect_backend(struct xenbus_device *dev,
+                                  struct xenkbd_info *info)
+{
+        int ret, evtchn;
+        struct xenbus_transaction xbt;
+
+        ret = xenbus_alloc_evtchn(dev, &evtchn);
+        if (ret)
+                return ret;
+        ret = bind_evtchn_to_irqhandler(evtchn, input_handler,
+                                        0, dev->devicetype, info);
+        if (ret < 0) {
+                xenbus_free_evtchn(dev, evtchn);
+                xenbus_dev_fatal(dev, ret, "bind_evtchn_to_irqhandler");
+                return ret;
+        }
+        info->irq = ret;
+
+ again:
+        ret = xenbus_transaction_start(&xbt);
+        if (ret) {
+                xenbus_dev_fatal(dev, ret, "starting transaction");
+                return ret;
+        }
+        ret = xenbus_printf(xbt, dev->nodename, "page-ref", "%lu",
+                            virt_to_mfn(info->page));
+        if (ret)
+                goto error_xenbus;
+        ret = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
+                            evtchn);
+        if (ret)
+                goto error_xenbus;
+        ret = xenbus_transaction_end(xbt, 0);
+        if (ret) {
+                if (ret == -EAGAIN)
+                        goto again;
+                xenbus_dev_fatal(dev, ret, "completing transaction");
+                return ret;
+        }
+
+        xenbus_switch_state(dev, XenbusStateInitialised);
+        return 0;
+
+ error_xenbus:
+        xenbus_transaction_end(xbt, 1);
+        xenbus_dev_fatal(dev, ret, "writing xenstore");
+        return ret;
+}
+
+static void xenkbd_disconnect_backend(struct xenkbd_info *info)
+{
+        if (info->irq >= 0)
+                unbind_from_irqhandler(info->irq, info);
+        info->irq = -1;
+}
+
+static void xenkbd_backend_changed(struct xenbus_device *dev,
+                                   enum xenbus_state backend_state)
+{
+        struct xenkbd_info *info = dev->dev.driver_data;
+        int ret, val;
+
+        switch (backend_state) {
+        case XenbusStateInitialising:
+        case XenbusStateInitialised:
+        case XenbusStateUnknown:
+        case XenbusStateClosed:
+                break;
+
+        case XenbusStateInitWait:
+InitWait:
+                ret = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
+                                   "feature-abs-pointer", "%d", &val);
+                if (ret < 0)
+                        val = 0;
+                if (val) {
+                        ret = xenbus_printf(XBT_NIL, info->xbdev->nodename,
+                                            "request-abs-pointer", "1");
+                        if (ret)
+                                printk(KERN_WARNING
+                                       "xenkbd: can't request abs-pointer");
+                }
+                xenbus_switch_state(dev, XenbusStateConnected);
+                break;
+
+        case XenbusStateConnected:
+                /*
+                 * Work around xenbus race condition: If backend goes
+                 * through InitWait to Connected fast enough, we can
+                 * get Connected twice here.
+                 */
+                if (dev->state != XenbusStateConnected)
+                        goto InitWait; /* no InitWait seen yet, fudge it */
+                break;
+
+        case XenbusStateClosing:
+                xenbus_frontend_closed(dev);
+                break;
+        }
+}
+
+static struct xenbus_device_id xenkbd_ids[] = {
+        { "vkbd" },
+        { "" }
+};
+
+static struct xenbus_driver xenkbd = {
+        .name = "vkbd",
+        .owner = THIS_MODULE,
+        .ids = xenkbd_ids,
+        .probe = xenkbd_probe,
+        .remove = xenkbd_remove,
+        .resume = xenkbd_resume,
+        .otherend_changed = xenkbd_backend_changed,
+};
+
+static int __init xenkbd_init(void)
+{
+        if (!is_running_on_xen())
+                return -ENODEV;
+
+        /* Nothing to do if running in dom0. */
+        if (is_initial_xendomain())
+                return -ENODEV;
+
+        return xenbus_register_frontend(&xenkbd);
+}
+
+static void __exit xenkbd_cleanup(void)
+{
+        xenbus_unregister_driver(&xenkbd);
+}
+
+module_init(xenkbd_init);
+module_exit(xenkbd_cleanup);
+
+MODULE_LICENSE("GPL");
diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
index 1bd5fb30237d..e3dc8f8d0c3e 100644
--- a/drivers/video/Kconfig
+++ b/drivers/video/Kconfig
@@ -1930,6 +1930,20 @@ config FB_VIRTUAL
 
           If unsure, say N.
 
+config XEN_FBDEV_FRONTEND
+        tristate "Xen virtual frame buffer support"
+        depends on FB && XEN
+        select FB_SYS_FILLRECT
+        select FB_SYS_COPYAREA
+        select FB_SYS_IMAGEBLIT
+        select FB_SYS_FOPS
+        select FB_DEFERRED_IO
+        default y
+        help
+          This driver implements the front-end of the Xen virtual
+          frame buffer driver.  It communicates with a back-end
+          in another domain.
+
 source "drivers/video/omap/Kconfig"
 
 source "drivers/video/backlight/Kconfig"
diff --git a/drivers/video/Makefile b/drivers/video/Makefile
index 11c0e5e05f21..f172b9b73314 100644
--- a/drivers/video/Makefile
+++ b/drivers/video/Makefile
@@ -114,6 +114,7 @@ obj-$(CONFIG_FB_PS3)		  += ps3fb.o
 obj-$(CONFIG_FB_SM501)            += sm501fb.o
 obj-$(CONFIG_FB_XILINX)           += xilinxfb.o
 obj-$(CONFIG_FB_OMAP)             += omap/
+obj-$(CONFIG_XEN_FBDEV_FRONTEND)  += xen-fbfront.o
 
 # Platform or fallback drivers go here
 obj-$(CONFIG_FB_UVESA)            += uvesafb.o
diff --git a/drivers/video/xen-fbfront.c b/drivers/video/xen-fbfront.c
new file mode 100644
index 000000000000..619a6f8d65a2
--- /dev/null
+++ b/drivers/video/xen-fbfront.c
@@ -0,0 +1,550 @@
+/*
+ * Xen para-virtual frame buffer device
+ *
+ * Copyright (C) 2005-2006 Anthony Liguori <aliguori@us.ibm.com>
+ * Copyright (C) 2006-2008 Red Hat, Inc., Markus Armbruster <armbru@redhat.com>
+ *
+ *  Based on linux/drivers/video/q40fb.c
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License. See the file COPYING in the main directory of this archive for
+ *  more details.
+ */
+
+/*
+ * TODO:
+ *
+ * Switch to grant tables when they become capable of dealing with the
+ * frame buffer.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fb.h>
+#include <linux/module.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
+#include <asm/xen/hypervisor.h>
+#include <xen/events.h>
+#include <xen/page.h>
+#include <xen/interface/io/fbif.h>
+#include <xen/interface/io/protocols.h>
+#include <xen/xenbus.h>
+
+struct xenfb_info {
+        unsigned char           *fb;
+        struct fb_info          *fb_info;
+        int                     x1, y1, x2, y2; /* dirty rectangle,
+                                                   protected by dirty_lock */
+        spinlock_t              dirty_lock;
+        int                     nr_pages;
+        int                     irq;
+        struct xenfb_page       *page;
+        unsigned long           *mfns;
+        int                     update_wanted; /* XENFB_TYPE_UPDATE wanted */
+
+        struct xenbus_device    *xbdev;
+};
+
+static u32 xenfb_mem_len = XENFB_WIDTH * XENFB_HEIGHT * XENFB_DEPTH / 8;
+
+static int xenfb_remove(struct xenbus_device *);
+static void xenfb_init_shared_page(struct xenfb_info *);
+static int xenfb_connect_backend(struct xenbus_device *, struct xenfb_info *);
+static void xenfb_disconnect_backend(struct xenfb_info *);
+
+static void xenfb_do_update(struct xenfb_info *info,
+                            int x, int y, int w, int h)
+{
+        union xenfb_out_event event;
+        u32 prod;
+
+        event.type = XENFB_TYPE_UPDATE;
+        event.update.x = x;
+        event.update.y = y;
+        event.update.width = w;
+        event.update.height = h;
+
+        prod = info->page->out_prod;
+        /* caller ensures !xenfb_queue_full() */
+        mb();                   /* ensure ring space available */
+        XENFB_OUT_RING_REF(info->page, prod) = event;
+        wmb();                  /* ensure ring contents visible */
+        info->page->out_prod = prod + 1;
+
+        notify_remote_via_irq(info->irq);
+}
+
+static int xenfb_queue_full(struct xenfb_info *info)
+{
+        u32 cons, prod;
+
+        prod = info->page->out_prod;
+        cons = info->page->out_cons;
+        return prod - cons == XENFB_OUT_RING_LEN;
+}
+
+static void xenfb_refresh(struct xenfb_info *info,
+                          int x1, int y1, int w, int h)
+{
+        unsigned long flags;
+        int y2 = y1 + h - 1;
+        int x2 = x1 + w - 1;
+
+        if (!info->update_wanted)
+                return;
+
+        spin_lock_irqsave(&info->dirty_lock, flags);
+
+        /* Combine with dirty rectangle: */
+        if (info->y1 < y1)
+                y1 = info->y1;
+        if (info->y2 > y2)
+                y2 = info->y2;
+        if (info->x1 < x1)
+                x1 = info->x1;
+        if (info->x2 > x2)
+                x2 = info->x2;
+
+        if (xenfb_queue_full(info)) {
+                /* Can't send right now, stash it in the dirty rectangle */
+                info->x1 = x1;
+                info->x2 = x2;
+                info->y1 = y1;
+                info->y2 = y2;
+                spin_unlock_irqrestore(&info->dirty_lock, flags);
+                return;
+        }
+
+        /* Clear dirty rectangle: */
+        info->x1 = info->y1 = INT_MAX;
+        info->x2 = info->y2 = 0;
+
+        spin_unlock_irqrestore(&info->dirty_lock, flags);
+
+        if (x1 <= x2 && y1 <= y2)
+                xenfb_do_update(info, x1, y1, x2 - x1 + 1, y2 - y1 + 1);
+}
+
+static void xenfb_deferred_io(struct fb_info *fb_info,
+                              struct list_head *pagelist)
+{
+        struct xenfb_info *info = fb_info->par;
+        struct page *page;
+        unsigned long beg, end;
+        int y1, y2, miny, maxy;
+
+        miny = INT_MAX;
+        maxy = 0;
+        list_for_each_entry(page, pagelist, lru) {
+                beg = page->index << PAGE_SHIFT;
+                end = beg + PAGE_SIZE - 1;
+                y1 = beg / fb_info->fix.line_length;
+                y2 = end / fb_info->fix.line_length;
+                if (y2 >= fb_info->var.yres)
+                        y2 = fb_info->var.yres - 1;
+                if (miny > y1)
+                        miny = y1;
+                if (maxy < y2)
+                        maxy = y2;
+        }
+        xenfb_refresh(info, 0, miny, fb_info->var.xres, maxy - miny + 1);
+}
+
+static struct fb_deferred_io xenfb_defio = {
+        .delay          = HZ / 20,
+        .deferred_io    = xenfb_deferred_io,
+};
+
+static int xenfb_setcolreg(unsigned regno, unsigned red, unsigned green,
+                           unsigned blue, unsigned transp,
+                           struct fb_info *info)
+{
+        u32 v;
+
+        if (regno > info->cmap.len)
+                return 1;
+
+#define CNVT_TOHW(val, width) ((((val)<<(width))+0x7FFF-(val))>>16)
+        red = CNVT_TOHW(red, info->var.red.length);
+        green = CNVT_TOHW(green, info->var.green.length);
+        blue = CNVT_TOHW(blue, info->var.blue.length);
+        transp = CNVT_TOHW(transp, info->var.transp.length);
+#undef CNVT_TOHW
+
+        v = (red << info->var.red.offset) |
+            (green << info->var.green.offset) |
+            (blue << info->var.blue.offset);
+
+        switch (info->var.bits_per_pixel) {
+        case 16:
+        case 24:
+        case 32:
+                ((u32 *)info->pseudo_palette)[regno] = v;
+                break;
+        }
+
+        return 0;
+}
+
+static void xenfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
+{
+        struct xenfb_info *info = p->par;
+
+        sys_fillrect(p, rect);
+        xenfb_refresh(info, rect->dx, rect->dy, rect->width, rect->height);
+}
+
+static void xenfb_imageblit(struct fb_info *p, const struct fb_image *image)
+{
+        struct xenfb_info *info = p->par;
+
+        sys_imageblit(p, image);
+        xenfb_refresh(info, image->dx, image->dy, image->width, image->height);
+}
+
+static void xenfb_copyarea(struct fb_info *p, const struct fb_copyarea *area)
+{
+        struct xenfb_info *info = p->par;
+
+        sys_copyarea(p, area);
+        xenfb_refresh(info, area->dx, area->dy, area->width, area->height);
+}
+
+static ssize_t xenfb_write(struct fb_info *p, const char __user *buf,
+                        size_t count, loff_t *ppos)
+{
+        struct xenfb_info *info = p->par;
+        ssize_t res;
+
+        res = fb_sys_write(p, buf, count, ppos);
+        xenfb_refresh(info, 0, 0, info->page->width, info->page->height);
+        return res;
+}
+
+static struct fb_ops xenfb_fb_ops = {
+        .owner          = THIS_MODULE,
+        .fb_read        = fb_sys_read,
+        .fb_write       = xenfb_write,
+        .fb_setcolreg   = xenfb_setcolreg,
+        .fb_fillrect    = xenfb_fillrect,
+        .fb_copyarea    = xenfb_copyarea,
+        .fb_imageblit   = xenfb_imageblit,
+};
+
+static irqreturn_t xenfb_event_handler(int rq, void *dev_id)
+{
+        /*
+         * No in events recognized, simply ignore them all.
+         * If you need to recognize some, see xen-kbdfront's
+         * input_handler() for how to do that.
+         */
+        struct xenfb_info *info = dev_id;
+        struct xenfb_page *page = info->page;
+
+        if (page->in_cons != page->in_prod) {
+                info->page->in_cons = info->page->in_prod;
+                notify_remote_via_irq(info->irq);
+        }
+
+        /* Flush dirty rectangle: */
+        xenfb_refresh(info, INT_MAX, INT_MAX, -INT_MAX, -INT_MAX);
+
+        return IRQ_HANDLED;
+}
+
+static int __devinit xenfb_probe(struct xenbus_device *dev,
+                                 const struct xenbus_device_id *id)
+{
+        struct xenfb_info *info;
+        struct fb_info *fb_info;
+        int ret;
+
+        info = kzalloc(sizeof(*info), GFP_KERNEL);
+        if (info == NULL) {
+                xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
+                return -ENOMEM;
+        }
+        dev->dev.driver_data = info;
+        info->xbdev = dev;
+        info->irq = -1;
+        info->x1 = info->y1 = INT_MAX;
+        spin_lock_init(&info->dirty_lock);
+
+        info->fb = vmalloc(xenfb_mem_len);
+        if (info->fb == NULL)
+                goto error_nomem;
+        memset(info->fb, 0, xenfb_mem_len);
+
+        info->nr_pages = (xenfb_mem_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+        info->mfns = vmalloc(sizeof(unsigned long) * info->nr_pages);
+        if (!info->mfns)
+                goto error_nomem;
+
+        /* set up shared page */
+        info->page = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+        if (!info->page)
+                goto error_nomem;
+
+        xenfb_init_shared_page(info);
+
+        /* abusing framebuffer_alloc() to allocate pseudo_palette */
+        fb_info = framebuffer_alloc(sizeof(u32) * 256, NULL);
+        if (fb_info == NULL)
+                goto error_nomem;
+
+        /* complete the abuse: */
+        fb_info->pseudo_palette = fb_info->par;
+        fb_info->par = info;
+
+        fb_info->screen_base = info->fb;
+
+        fb_info->fbops = &xenfb_fb_ops;
+        fb_info->var.xres_virtual = fb_info->var.xres = info->page->width;
+        fb_info->var.yres_virtual = fb_info->var.yres = info->page->height;
+        fb_info->var.bits_per_pixel = info->page->depth;
+
+        fb_info->var.red = (struct fb_bitfield){16, 8, 0};
+        fb_info->var.green = (struct fb_bitfield){8, 8, 0};
+        fb_info->var.blue = (struct fb_bitfield){0, 8, 0};
+
+        fb_info->var.activate = FB_ACTIVATE_NOW;
+        fb_info->var.height = -1;
+        fb_info->var.width = -1;
+        fb_info->var.vmode = FB_VMODE_NONINTERLACED;
+
+        fb_info->fix.visual = FB_VISUAL_TRUECOLOR;
+        fb_info->fix.line_length = info->page->line_length;
+        fb_info->fix.smem_start = 0;
+        fb_info->fix.smem_len = xenfb_mem_len;
+        strcpy(fb_info->fix.id, "xen");
+        fb_info->fix.type = FB_TYPE_PACKED_PIXELS;
+        fb_info->fix.accel = FB_ACCEL_NONE;
+
+        fb_info->flags = FBINFO_FLAG_DEFAULT;
+
+        ret = fb_alloc_cmap(&fb_info->cmap, 256, 0);
+        if (ret < 0) {
+                framebuffer_release(fb_info);
+                xenbus_dev_fatal(dev, ret, "fb_alloc_cmap");
+                goto error;
+        }
+
+        fb_info->fbdefio = &xenfb_defio;
+        fb_deferred_io_init(fb_info);
+
+        ret = register_framebuffer(fb_info);
+        if (ret) {
+                fb_deferred_io_cleanup(fb_info);
+                fb_dealloc_cmap(&fb_info->cmap);
+                framebuffer_release(fb_info);
+                xenbus_dev_fatal(dev, ret, "register_framebuffer");
+                goto error;
+        }
+        info->fb_info = fb_info;
+
+        ret = xenfb_connect_backend(dev, info);
+        if (ret < 0)
+                goto error;
+
+        return 0;
+
+ error_nomem:
+        ret = -ENOMEM;
+        xenbus_dev_fatal(dev, ret, "allocating device memory");
+ error:
+        xenfb_remove(dev);
+        return ret;
+}
+
+static int xenfb_resume(struct xenbus_device *dev)
+{
+        struct xenfb_info *info = dev->dev.driver_data;
+
+        xenfb_disconnect_backend(info);
+        xenfb_init_shared_page(info);
+        return xenfb_connect_backend(dev, info);
+}
+
+static int xenfb_remove(struct xenbus_device *dev)
+{
+        struct xenfb_info *info = dev->dev.driver_data;
+
+        xenfb_disconnect_backend(info);
+        if (info->fb_info) {
+                fb_deferred_io_cleanup(info->fb_info);
+                unregister_framebuffer(info->fb_info);
+                fb_dealloc_cmap(&info->fb_info->cmap);
+                framebuffer_release(info->fb_info);
+        }
+        free_page((unsigned long)info->page);
+        vfree(info->mfns);
+        vfree(info->fb);
+        kfree(info);
+
+        return 0;
+}
+
+static unsigned long vmalloc_to_mfn(void *address)
+{
+        return pfn_to_mfn(vmalloc_to_pfn(address));
+}
+
+static void xenfb_init_shared_page(struct xenfb_info *info)
+{
+        int i;
+
+        for (i = 0; i < info->nr_pages; i++)
+                info->mfns[i] = vmalloc_to_mfn(info->fb + i * PAGE_SIZE);
+
+        info->page->pd[0] = vmalloc_to_mfn(info->mfns);
+        info->page->pd[1] = 0;
+        info->page->width = XENFB_WIDTH;
+        info->page->height = XENFB_HEIGHT;
+        info->page->depth = XENFB_DEPTH;
+        info->page->line_length = (info->page->depth / 8) * info->page->width;
+        info->page->mem_length = xenfb_mem_len;
+        info->page->in_cons = info->page->in_prod = 0;
+        info->page->out_cons = info->page->out_prod = 0;
+}
+
+static int xenfb_connect_backend(struct xenbus_device *dev,
+                                 struct xenfb_info *info)
+{
+        int ret, evtchn;
+        struct xenbus_transaction xbt;
+
+        ret = xenbus_alloc_evtchn(dev, &evtchn);
+        if (ret)
+                return ret;
+        ret = bind_evtchn_to_irqhandler(evtchn, xenfb_event_handler,
+                                        0, dev->devicetype, info);
+        if (ret < 0) {
+                xenbus_free_evtchn(dev, evtchn);
+                xenbus_dev_fatal(dev, ret, "bind_evtchn_to_irqhandler");
+                return ret;
+        }
+        info->irq = ret;
+
+ again:
+        ret = xenbus_transaction_start(&xbt);
+        if (ret) {
+                xenbus_dev_fatal(dev, ret, "starting transaction");
+                return ret;
+        }
+        ret = xenbus_printf(xbt, dev->nodename, "page-ref", "%lu",
+                            virt_to_mfn(info->page));
+        if (ret)
+                goto error_xenbus;
+        ret = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
+                            evtchn);
+        if (ret)
+                goto error_xenbus;
+        ret = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
+                            XEN_IO_PROTO_ABI_NATIVE);
+        if (ret)
+                goto error_xenbus;
+        ret = xenbus_printf(xbt, dev->nodename, "feature-update", "1");
+        if (ret)
+                goto error_xenbus;
+        ret = xenbus_transaction_end(xbt, 0);
+        if (ret) {
+                if (ret == -EAGAIN)
+                        goto again;
+                xenbus_dev_fatal(dev, ret, "completing transaction");
+                return ret;
+        }
+
+        xenbus_switch_state(dev, XenbusStateInitialised);
+        return 0;
+
+ error_xenbus:
+        xenbus_transaction_end(xbt, 1);
+        xenbus_dev_fatal(dev, ret, "writing xenstore");
+        return ret;
+}
+
+static void xenfb_disconnect_backend(struct xenfb_info *info)
+{
+        if (info->irq >= 0)
+                unbind_from_irqhandler(info->irq, info);
+        info->irq = -1;
+}
+
+static void xenfb_backend_changed(struct xenbus_device *dev,
+                                  enum xenbus_state backend_state)
+{
+        struct xenfb_info *info = dev->dev.driver_data;
+        int val;
+
+        switch (backend_state) {
+        case XenbusStateInitialising:
+        case XenbusStateInitialised:
+        case XenbusStateUnknown:
+        case XenbusStateClosed:
+                break;
+
+        case XenbusStateInitWait:
+InitWait:
+                xenbus_switch_state(dev, XenbusStateConnected);
+                break;
+
+        case XenbusStateConnected:
+                /*
+                 * Work around xenbus race condition: If backend goes
+                 * through InitWait to Connected fast enough, we can
+                 * get Connected twice here.
+                 */
+                if (dev->state != XenbusStateConnected)
+                        goto InitWait; /* no InitWait seen yet, fudge it */
+
+                if (xenbus_scanf(XBT_NIL, info->xbdev->otherend,
+                                 "request-update", "%d", &val) < 0)
+                        val = 0;
+                if (val)
+                        info->update_wanted = 1;
+                break;
+
+        case XenbusStateClosing:
+                xenbus_frontend_closed(dev);
+                break;
+        }
+}
+
+static struct xenbus_device_id xenfb_ids[] = {
+        { "vfb" },
+        { "" }
+};
+
+static struct xenbus_driver xenfb = {
+        .name = "vfb",
+        .owner = THIS_MODULE,
+        .ids = xenfb_ids,
+        .probe = xenfb_probe,
+        .remove = xenfb_remove,
+        .resume = xenfb_resume,
+        .otherend_changed = xenfb_backend_changed,
+};
+
+static int __init xenfb_init(void)
+{
+        if (!is_running_on_xen())
+                return -ENODEV;
+
+        /* Nothing to do if running in dom0. */
+        if (is_initial_xendomain())
+                return -ENODEV;
+
+        return xenbus_register_frontend(&xenfb);
+}
+
+static void __exit xenfb_cleanup(void)
+{
+        xenbus_unregister_driver(&xenfb);
+}
+
+module_init(xenfb_init);
+module_exit(xenfb_cleanup);
+
+MODULE_LICENSE("GPL");