1 files changed, 719 insertions, 0 deletions

diff --git a/drivers/video/fbdev/xen-fbfront.c b/drivers/video/fbdev/xen-fbfront.c
new file mode 100644
index 000000000000..901014bbc821
--- /dev/null
+++ b/drivers/video/fbdev/xen-fbfront.c
@@ -0,0 +1,719 @@
+/*
+ * 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/console.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fb.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
+
+#include <asm/xen/hypervisor.h>
+
+#include <xen/xen.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>
+#include <xen/platform_pci.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 */
+        int                     feature_resize; /* XENFB_TYPE_RESIZE ok */
+        struct xenfb_resize     resize;         /* protected by resize_lock */
+        int                     resize_dpy;     /* ditto */
+        spinlock_t              resize_lock;
+
+        struct xenbus_device    *xbdev;
+};
+
+#define XENFB_DEFAULT_FB_LEN (XENFB_WIDTH * XENFB_HEIGHT * XENFB_DEPTH / 8)
+
+enum { KPARAM_MEM, KPARAM_WIDTH, KPARAM_HEIGHT, KPARAM_CNT };
+static int video[KPARAM_CNT] = { 2, XENFB_WIDTH, XENFB_HEIGHT };
+module_param_array(video, int, NULL, 0);
+MODULE_PARM_DESC(video,
+        "Video memory size in MB, width, height in pixels (default 2,800,600)");
+
+static void xenfb_make_preferred_console(void);
+static int xenfb_remove(struct xenbus_device *);
+static void xenfb_init_shared_page(struct xenfb_info *, struct fb_info *);
+static int xenfb_connect_backend(struct xenbus_device *, struct xenfb_info *);
+static void xenfb_disconnect_backend(struct xenfb_info *);
+
+static void xenfb_send_event(struct xenfb_info *info,
+                             union xenfb_out_event *event)
+{
+        u32 prod;
+
+        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 void xenfb_do_update(struct xenfb_info *info,
+                            int x, int y, int w, int h)
+{
+        union xenfb_out_event event;
+
+        memset(&event, 0, sizeof(event));
+        event.type = XENFB_TYPE_UPDATE;
+        event.update.x = x;
+        event.update.y = y;
+        event.update.width = w;
+        event.update.height = h;
+
+        /* caller ensures !xenfb_queue_full() */
+        xenfb_send_event(info, &event);
+}
+
+static void xenfb_do_resize(struct xenfb_info *info)
+{
+        union xenfb_out_event event;
+
+        memset(&event, 0, sizeof(event));
+        event.resize = info->resize;
+
+        /* caller ensures !xenfb_queue_full() */
+        xenfb_send_event(info, &event);
+}
+
+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_handle_resize_dpy(struct xenfb_info *info)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&info->resize_lock, flags);
+        if (info->resize_dpy) {
+                if (!xenfb_queue_full(info)) {
+                        info->resize_dpy = 0;
+                        xenfb_do_resize(info);
+                }
+        }
+        spin_unlock_irqrestore(&info->resize_lock, flags);
+}
+
+static void xenfb_refresh(struct xenfb_info *info,
+                          int x1, int y1, int w, int h)
+{
+        unsigned long flags;
+        int x2 = x1 + w - 1;
+        int y2 = y1 + h - 1;
+
+        xenfb_handle_resize_dpy(info);
+
+        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 int
+xenfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
+{
+        struct xenfb_info *xenfb_info;
+        int required_mem_len;
+
+        xenfb_info = info->par;
+
+        if (!xenfb_info->feature_resize) {
+                if (var->xres == video[KPARAM_WIDTH] &&
+                    var->yres == video[KPARAM_HEIGHT] &&
+                    var->bits_per_pixel == xenfb_info->page->depth) {
+                        return 0;
+                }
+                return -EINVAL;
+        }
+
+        /* Can't resize past initial width and height */
+        if (var->xres > video[KPARAM_WIDTH] || var->yres > video[KPARAM_HEIGHT])
+                return -EINVAL;
+
+        required_mem_len = var->xres * var->yres * xenfb_info->page->depth / 8;
+        if (var->bits_per_pixel == xenfb_info->page->depth &&
+            var->xres <= info->fix.line_length / (XENFB_DEPTH / 8) &&
+            required_mem_len <= info->fix.smem_len) {
+                var->xres_virtual = var->xres;
+                var->yres_virtual = var->yres;
+                return 0;
+        }
+        return -EINVAL;
+}
+
+static int xenfb_set_par(struct fb_info *info)
+{
+        struct xenfb_info *xenfb_info;
+        unsigned long flags;
+
+        xenfb_info = info->par;
+
+        spin_lock_irqsave(&xenfb_info->resize_lock, flags);
+        xenfb_info->resize.type = XENFB_TYPE_RESIZE;
+        xenfb_info->resize.width = info->var.xres;
+        xenfb_info->resize.height = info->var.yres;
+        xenfb_info->resize.stride = info->fix.line_length;
+        xenfb_info->resize.depth = info->var.bits_per_pixel;
+        xenfb_info->resize.offset = 0;
+        xenfb_info->resize_dpy = 1;
+        spin_unlock_irqrestore(&xenfb_info->resize_lock, flags);
+        return 0;
+}
+
+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,
+        .fb_check_var   = xenfb_check_var,
+        .fb_set_par     = xenfb_set_par,
+};
+
+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 xenfb_probe(struct xenbus_device *dev,
+                       const struct xenbus_device_id *id)
+{
+        struct xenfb_info *info;
+        struct fb_info *fb_info;
+        int fb_size;
+        int val;
+        int ret = 0;
+
+        info = kzalloc(sizeof(*info), GFP_KERNEL);
+        if (info == NULL) {
+                xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
+                return -ENOMEM;
+        }
+
+        /* Limit kernel param videoram amount to what is in xenstore */
+        if (xenbus_scanf(XBT_NIL, dev->otherend, "videoram", "%d", &val) == 1) {
+                if (val < video[KPARAM_MEM])
+                        video[KPARAM_MEM] = val;
+        }
+
+        /* If requested res does not fit in available memory, use default */
+        fb_size = video[KPARAM_MEM] * 1024 * 1024;
+        if (video[KPARAM_WIDTH] * video[KPARAM_HEIGHT] * XENFB_DEPTH / 8
+            > fb_size) {
+                video[KPARAM_WIDTH] = XENFB_WIDTH;
+                video[KPARAM_HEIGHT] = XENFB_HEIGHT;
+                fb_size = XENFB_DEFAULT_FB_LEN;
+        }
+
+        dev_set_drvdata(&dev->dev, info);
+        info->xbdev = dev;
+        info->irq = -1;
+        info->x1 = info->y1 = INT_MAX;
+        spin_lock_init(&info->dirty_lock);
+        spin_lock_init(&info->resize_lock);
+
+        info->fb = vzalloc(fb_size);
+        if (info->fb == NULL)
+                goto error_nomem;
+
+        info->nr_pages = (fb_size + 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;
+
+        /* 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 = video[KPARAM_WIDTH];
+        fb_info->var.yres_virtual = fb_info->var.yres = video[KPARAM_HEIGHT];
+        fb_info->var.bits_per_pixel = XENFB_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 = fb_info->var.xres * XENFB_DEPTH / 8;
+        fb_info->fix.smem_start = 0;
+        fb_info->fix.smem_len = fb_size;
+        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 | FBINFO_VIRTFB;
+
+        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);
+
+        xenfb_init_shared_page(info, fb_info);
+
+        ret = xenfb_connect_backend(dev, info);
+        if (ret < 0) {
+                xenbus_dev_fatal(dev, ret, "xenfb_connect_backend");
+                goto error_fb;
+        }
+
+        ret = register_framebuffer(fb_info);
+        if (ret) {
+                xenbus_dev_fatal(dev, ret, "register_framebuffer");
+                goto error_fb;
+        }
+        info->fb_info = fb_info;
+
+        xenfb_make_preferred_console();
+        return 0;
+
+error_fb:
+        fb_deferred_io_cleanup(fb_info);
+        fb_dealloc_cmap(&fb_info->cmap);
+        framebuffer_release(fb_info);
+error_nomem:
+        if (!ret) {
+                ret = -ENOMEM;
+                xenbus_dev_fatal(dev, ret, "allocating device memory");
+        }
+error:
+        xenfb_remove(dev);
+        return ret;
+}
+
+static void xenfb_make_preferred_console(void)
+{
+        struct console *c;
+
+        if (console_set_on_cmdline)
+                return;
+
+        console_lock();
+        for_each_console(c) {
+                if (!strcmp(c->name, "tty") && c->index == 0)
+                        break;
+        }
+        console_unlock();
+        if (c) {
+                unregister_console(c);
+                c->flags |= CON_CONSDEV;
+                c->flags &= ~CON_PRINTBUFFER; /* don't print again */
+                register_console(c);
+        }
+}
+
+static int xenfb_resume(struct xenbus_device *dev)
+{
+        struct xenfb_info *info = dev_get_drvdata(&dev->dev);
+
+        xenfb_disconnect_backend(info);
+        xenfb_init_shared_page(info, info->fb_info);
+        return xenfb_connect_backend(dev, info);
+}
+
+static int xenfb_remove(struct xenbus_device *dev)
+{
+        struct xenfb_info *info = dev_get_drvdata(&dev->dev);
+
+        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,
+                                   struct fb_info *fb_info)
+{
+        int i;
+        int epd = PAGE_SIZE / sizeof(info->mfns[0]);
+
+        for (i = 0; i < info->nr_pages; i++)
+                info->mfns[i] = vmalloc_to_mfn(info->fb + i * PAGE_SIZE);
+
+        for (i = 0; i * epd < info->nr_pages; i++)
+                info->page->pd[i] = vmalloc_to_mfn(&info->mfns[i * epd]);
+
+        info->page->width = fb_info->var.xres;
+        info->page->height = fb_info->var.yres;
+        info->page->depth = fb_info->var.bits_per_pixel;
+        info->page->line_length = fb_info->fix.line_length;
+        info->page->mem_length = fb_info->fix.smem_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, irq;
+        struct xenbus_transaction xbt;
+
+        ret = xenbus_alloc_evtchn(dev, &evtchn);
+        if (ret)
+                return ret;
+        irq = bind_evtchn_to_irqhandler(evtchn, xenfb_event_handler,
+                                        0, dev->devicetype, info);
+        if (irq < 0) {
+                xenbus_free_evtchn(dev, evtchn);
+                xenbus_dev_fatal(dev, ret, "bind_evtchn_to_irqhandler");
+                return irq;
+        }
+ again:
+        ret = xenbus_transaction_start(&xbt);
+        if (ret) {
+                xenbus_dev_fatal(dev, ret, "starting transaction");
+                goto unbind_irq;
+        }
+        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");
+                goto unbind_irq;
+        }
+
+        xenbus_switch_state(dev, XenbusStateInitialised);
+        info->irq = irq;
+        return 0;
+
+ error_xenbus:
+        xenbus_transaction_end(xbt, 1);
+        xenbus_dev_fatal(dev, ret, "writing xenstore");
+ unbind_irq:
+        unbind_from_irqhandler(irq, info);
+        return ret;
+}
+
+static void xenfb_disconnect_backend(struct xenfb_info *info)
+{
+        /* Prevent xenfb refresh */
+        info->update_wanted = 0;
+        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_get_drvdata(&dev->dev);
+        int val;
+
+        switch (backend_state) {
+        case XenbusStateInitialising:
+        case XenbusStateInitialised:
+        case XenbusStateReconfiguring:
+        case XenbusStateReconfigured:
+        case XenbusStateUnknown:
+                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;
+
+                if (xenbus_scanf(XBT_NIL, dev->otherend,
+                                 "feature-resize", "%d", &val) < 0)
+                        val = 0;
+                info->feature_resize = val;
+                break;
+
+        case XenbusStateClosed:
+                if (dev->state == XenbusStateClosed)
+                        break;
+                /* Missed the backend's CLOSING state -- fallthrough */
+        case XenbusStateClosing:
+                xenbus_frontend_closed(dev);
+                break;
+        }
+}
+
+static const struct xenbus_device_id xenfb_ids[] = {
+        { "vfb" },
+        { "" }
+};
+
+static DEFINE_XENBUS_DRIVER(xenfb, ,
+        .probe = xenfb_probe,
+        .remove = xenfb_remove,
+        .resume = xenfb_resume,
+        .otherend_changed = xenfb_backend_changed,
+);
+
+static int __init xenfb_init(void)
+{
+        if (!xen_domain())
+                return -ENODEV;
+
+        /* Nothing to do if running in dom0. */
+        if (xen_initial_domain())
+                return -ENODEV;
+
+        if (!xen_has_pv_devices())
+                return -ENODEV;
+
+        return xenbus_register_frontend(&xenfb_driver);
+}
+
+static void __exit xenfb_cleanup(void)
+{
+        xenbus_unregister_driver(&xenfb_driver);
+}
+
+module_init(xenfb_init);
+module_exit(xenfb_cleanup);
+
+MODULE_DESCRIPTION("Xen virtual framebuffer device frontend");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("xen:vfb");