source: src/linux/universal/linux-3.18/drivers/video/fbdev/xen-fbfront.c @ 31885

Last change on this file since 31885 was 31885, checked in by brainslayer, 3 months ago

update

File size: 17.6 KB
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1/*
2 * Xen para-virtual frame buffer device
3 *
4 * Copyright (C) 2005-2006 Anthony Liguori <aliguori@us.ibm.com>
5 * Copyright (C) 2006-2008 Red Hat, Inc., Markus Armbruster <armbru@redhat.com>
6 *
7 *  Based on linux/drivers/video/q40fb.c
8 *
9 *  This file is subject to the terms and conditions of the GNU General Public
10 *  License. See the file COPYING in the main directory of this archive for
11 *  more details.
12 */
13
14/*
15 * TODO:
16 *
17 * Switch to grant tables when they become capable of dealing with the
18 * frame buffer.
19 */
20
21#include <linux/console.h>
22#include <linux/kernel.h>
23#include <linux/errno.h>
24#include <linux/fb.h>
25#include <linux/module.h>
26#include <linux/slab.h>
27#include <linux/vmalloc.h>
28#include <linux/mm.h>
29
30#include <asm/xen/hypervisor.h>
31
32#include <xen/xen.h>
33#include <xen/events.h>
34#include <xen/page.h>
35#include <xen/interface/io/fbif.h>
36#include <xen/interface/io/protocols.h>
37#include <xen/xenbus.h>
38#include <xen/platform_pci.h>
39
40struct xenfb_info {
41        unsigned char           *fb;
42        struct fb_info          *fb_info;
43        int                     x1, y1, x2, y2; /* dirty rectangle,
44                                                   protected by dirty_lock */
45        spinlock_t              dirty_lock;
46        int                     nr_pages;
47        int                     irq;
48        struct xenfb_page       *page;
49        unsigned long           *mfns;
50        int                     update_wanted; /* XENFB_TYPE_UPDATE wanted */
51        int                     feature_resize; /* XENFB_TYPE_RESIZE ok */
52        struct xenfb_resize     resize;         /* protected by resize_lock */
53        int                     resize_dpy;     /* ditto */
54        spinlock_t              resize_lock;
55
56        struct xenbus_device    *xbdev;
57};
58
59#define XENFB_DEFAULT_FB_LEN (XENFB_WIDTH * XENFB_HEIGHT * XENFB_DEPTH / 8)
60
61enum { KPARAM_MEM, KPARAM_WIDTH, KPARAM_HEIGHT, KPARAM_CNT };
62static int video[KPARAM_CNT] = { 2, XENFB_WIDTH, XENFB_HEIGHT };
63module_param_array(video, int, NULL, 0);
64MODULE_PARM_DESC(video,
65        "Video memory size in MB, width, height in pixels (default 2,800,600)");
66
67static void xenfb_make_preferred_console(void);
68static int xenfb_remove(struct xenbus_device *);
69static void xenfb_init_shared_page(struct xenfb_info *, struct fb_info *);
70static int xenfb_connect_backend(struct xenbus_device *, struct xenfb_info *);
71static void xenfb_disconnect_backend(struct xenfb_info *);
72
73static void xenfb_send_event(struct xenfb_info *info,
74                             union xenfb_out_event *event)
75{
76        u32 prod;
77
78        prod = info->page->out_prod;
79        /* caller ensures !xenfb_queue_full() */
80        mb();                   /* ensure ring space available */
81        XENFB_OUT_RING_REF(info->page, prod) = *event;
82        wmb();                  /* ensure ring contents visible */
83        info->page->out_prod = prod + 1;
84
85        notify_remote_via_irq(info->irq);
86}
87
88static void xenfb_do_update(struct xenfb_info *info,
89                            int x, int y, int w, int h)
90{
91        union xenfb_out_event event;
92
93        memset(&event, 0, sizeof(event));
94        event.type = XENFB_TYPE_UPDATE;
95        event.update.x = x;
96        event.update.y = y;
97        event.update.width = w;
98        event.update.height = h;
99
100        /* caller ensures !xenfb_queue_full() */
101        xenfb_send_event(info, &event);
102}
103
104static void xenfb_do_resize(struct xenfb_info *info)
105{
106        union xenfb_out_event event;
107
108        memset(&event, 0, sizeof(event));
109        event.resize = info->resize;
110
111        /* caller ensures !xenfb_queue_full() */
112        xenfb_send_event(info, &event);
113}
114
115static int xenfb_queue_full(struct xenfb_info *info)
116{
117        u32 cons, prod;
118
119        prod = info->page->out_prod;
120        cons = info->page->out_cons;
121        return prod - cons == XENFB_OUT_RING_LEN;
122}
123
124static void xenfb_handle_resize_dpy(struct xenfb_info *info)
125{
126        unsigned long flags;
127
128        spin_lock_irqsave(&info->resize_lock, flags);
129        if (info->resize_dpy) {
130                if (!xenfb_queue_full(info)) {
131                        info->resize_dpy = 0;
132                        xenfb_do_resize(info);
133                }
134        }
135        spin_unlock_irqrestore(&info->resize_lock, flags);
136}
137
138static void xenfb_refresh(struct xenfb_info *info,
139                          int x1, int y1, int w, int h)
140{
141        unsigned long flags;
142        int x2 = x1 + w - 1;
143        int y2 = y1 + h - 1;
144
145        xenfb_handle_resize_dpy(info);
146
147        if (!info->update_wanted)
148                return;
149
150        spin_lock_irqsave(&info->dirty_lock, flags);
151
152        /* Combine with dirty rectangle: */
153        if (info->y1 < y1)
154                y1 = info->y1;
155        if (info->y2 > y2)
156                y2 = info->y2;
157        if (info->x1 < x1)
158                x1 = info->x1;
159        if (info->x2 > x2)
160                x2 = info->x2;
161
162        if (xenfb_queue_full(info)) {
163                /* Can't send right now, stash it in the dirty rectangle */
164                info->x1 = x1;
165                info->x2 = x2;
166                info->y1 = y1;
167                info->y2 = y2;
168                spin_unlock_irqrestore(&info->dirty_lock, flags);
169                return;
170        }
171
172        /* Clear dirty rectangle: */
173        info->x1 = info->y1 = INT_MAX;
174        info->x2 = info->y2 = 0;
175
176        spin_unlock_irqrestore(&info->dirty_lock, flags);
177
178        if (x1 <= x2 && y1 <= y2)
179                xenfb_do_update(info, x1, y1, x2 - x1 + 1, y2 - y1 + 1);
180}
181
182static void xenfb_deferred_io(struct fb_info *fb_info,
183                              struct list_head *pagelist)
184{
185        struct xenfb_info *info = fb_info->par;
186        struct page *page;
187        unsigned long beg, end;
188        int y1, y2, miny, maxy;
189
190        miny = INT_MAX;
191        maxy = 0;
192        list_for_each_entry(page, pagelist, lru) {
193                beg = page->index << PAGE_SHIFT;
194                end = beg + PAGE_SIZE - 1;
195                y1 = beg / fb_info->fix.line_length;
196                y2 = end / fb_info->fix.line_length;
197                if (y2 >= fb_info->var.yres)
198                        y2 = fb_info->var.yres - 1;
199                if (miny > y1)
200                        miny = y1;
201                if (maxy < y2)
202                        maxy = y2;
203        }
204        xenfb_refresh(info, 0, miny, fb_info->var.xres, maxy - miny + 1);
205}
206
207static struct fb_deferred_io xenfb_defio = {
208        .delay          = HZ / 20,
209        .deferred_io    = xenfb_deferred_io,
210};
211
212static int xenfb_setcolreg(unsigned regno, unsigned red, unsigned green,
213                           unsigned blue, unsigned transp,
214                           struct fb_info *info)
215{
216        u32 v;
217
218        if (regno > info->cmap.len)
219                return 1;
220
221#define CNVT_TOHW(val, width) ((((val)<<(width))+0x7FFF-(val))>>16)
222        red = CNVT_TOHW(red, info->var.red.length);
223        green = CNVT_TOHW(green, info->var.green.length);
224        blue = CNVT_TOHW(blue, info->var.blue.length);
225        transp = CNVT_TOHW(transp, info->var.transp.length);
226#undef CNVT_TOHW
227
228        v = (red << info->var.red.offset) |
229            (green << info->var.green.offset) |
230            (blue << info->var.blue.offset);
231
232        switch (info->var.bits_per_pixel) {
233        case 16:
234        case 24:
235        case 32:
236                ((u32 *)info->pseudo_palette)[regno] = v;
237                break;
238        }
239
240        return 0;
241}
242
243static void xenfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
244{
245        struct xenfb_info *info = p->par;
246
247        sys_fillrect(p, rect);
248        xenfb_refresh(info, rect->dx, rect->dy, rect->width, rect->height);
249}
250
251static void xenfb_imageblit(struct fb_info *p, const struct fb_image *image)
252{
253        struct xenfb_info *info = p->par;
254
255        sys_imageblit(p, image);
256        xenfb_refresh(info, image->dx, image->dy, image->width, image->height);
257}
258
259static void xenfb_copyarea(struct fb_info *p, const struct fb_copyarea *area)
260{
261        struct xenfb_info *info = p->par;
262
263        sys_copyarea(p, area);
264        xenfb_refresh(info, area->dx, area->dy, area->width, area->height);
265}
266
267static ssize_t xenfb_write(struct fb_info *p, const char __user *buf,
268                        size_t count, loff_t *ppos)
269{
270        struct xenfb_info *info = p->par;
271        ssize_t res;
272
273        res = fb_sys_write(p, buf, count, ppos);
274        xenfb_refresh(info, 0, 0, info->page->width, info->page->height);
275        return res;
276}
277
278static int
279xenfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
280{
281        struct xenfb_info *xenfb_info;
282        int required_mem_len;
283
284        xenfb_info = info->par;
285
286        if (!xenfb_info->feature_resize) {
287                if (var->xres == video[KPARAM_WIDTH] &&
288                    var->yres == video[KPARAM_HEIGHT] &&
289                    var->bits_per_pixel == xenfb_info->page->depth) {
290                        return 0;
291                }
292                return -EINVAL;
293        }
294
295        /* Can't resize past initial width and height */
296        if (var->xres > video[KPARAM_WIDTH] || var->yres > video[KPARAM_HEIGHT])
297                return -EINVAL;
298
299        required_mem_len = var->xres * var->yres * xenfb_info->page->depth / 8;
300        if (var->bits_per_pixel == xenfb_info->page->depth &&
301            var->xres <= info->fix.line_length / (XENFB_DEPTH / 8) &&
302            required_mem_len <= info->fix.smem_len) {
303                var->xres_virtual = var->xres;
304                var->yres_virtual = var->yres;
305                return 0;
306        }
307        return -EINVAL;
308}
309
310static int xenfb_set_par(struct fb_info *info)
311{
312        struct xenfb_info *xenfb_info;
313        unsigned long flags;
314
315        xenfb_info = info->par;
316
317        spin_lock_irqsave(&xenfb_info->resize_lock, flags);
318        xenfb_info->resize.type = XENFB_TYPE_RESIZE;
319        xenfb_info->resize.width = info->var.xres;
320        xenfb_info->resize.height = info->var.yres;
321        xenfb_info->resize.stride = info->fix.line_length;
322        xenfb_info->resize.depth = info->var.bits_per_pixel;
323        xenfb_info->resize.offset = 0;
324        xenfb_info->resize_dpy = 1;
325        spin_unlock_irqrestore(&xenfb_info->resize_lock, flags);
326        return 0;
327}
328
329static struct fb_ops xenfb_fb_ops = {
330        .owner          = THIS_MODULE,
331        .fb_read        = fb_sys_read,
332        .fb_write       = xenfb_write,
333        .fb_setcolreg   = xenfb_setcolreg,
334        .fb_fillrect    = xenfb_fillrect,
335        .fb_copyarea    = xenfb_copyarea,
336        .fb_imageblit   = xenfb_imageblit,
337        .fb_check_var   = xenfb_check_var,
338        .fb_set_par     = xenfb_set_par,
339};
340
341static irqreturn_t xenfb_event_handler(int rq, void *dev_id)
342{
343        /*
344         * No in events recognized, simply ignore them all.
345         * If you need to recognize some, see xen-kbdfront's
346         * input_handler() for how to do that.
347         */
348        struct xenfb_info *info = dev_id;
349        struct xenfb_page *page = info->page;
350
351        if (page->in_cons != page->in_prod) {
352                info->page->in_cons = info->page->in_prod;
353                notify_remote_via_irq(info->irq);
354        }
355
356        /* Flush dirty rectangle: */
357        xenfb_refresh(info, INT_MAX, INT_MAX, -INT_MAX, -INT_MAX);
358
359        return IRQ_HANDLED;
360}
361
362static int xenfb_probe(struct xenbus_device *dev,
363                       const struct xenbus_device_id *id)
364{
365        struct xenfb_info *info;
366        struct fb_info *fb_info;
367        int fb_size;
368        int val;
369        int ret = 0;
370
371        info = kzalloc(sizeof(*info), GFP_KERNEL);
372        if (info == NULL) {
373                xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
374                return -ENOMEM;
375        }
376
377        /* Limit kernel param videoram amount to what is in xenstore */
378        if (xenbus_scanf(XBT_NIL, dev->otherend, "videoram", "%d", &val) == 1) {
379                if (val < video[KPARAM_MEM])
380                        video[KPARAM_MEM] = val;
381        }
382
383        /* If requested res does not fit in available memory, use default */
384        fb_size = video[KPARAM_MEM] * 1024 * 1024;
385        if (video[KPARAM_WIDTH] * video[KPARAM_HEIGHT] * XENFB_DEPTH / 8
386            > fb_size) {
387                video[KPARAM_WIDTH] = XENFB_WIDTH;
388                video[KPARAM_HEIGHT] = XENFB_HEIGHT;
389                fb_size = XENFB_DEFAULT_FB_LEN;
390        }
391
392        dev_set_drvdata(&dev->dev, info);
393        info->xbdev = dev;
394        info->irq = -1;
395        info->x1 = info->y1 = INT_MAX;
396        spin_lock_init(&info->dirty_lock);
397        spin_lock_init(&info->resize_lock);
398
399        info->fb = vzalloc(fb_size);
400        if (info->fb == NULL)
401                goto error_nomem;
402
403        info->nr_pages = (fb_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
404
405        info->mfns = vmalloc(sizeof(unsigned long) * info->nr_pages);
406        if (!info->mfns)
407                goto error_nomem;
408
409        /* set up shared page */
410        info->page = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
411        if (!info->page)
412                goto error_nomem;
413
414        /* abusing framebuffer_alloc() to allocate pseudo_palette */
415        fb_info = framebuffer_alloc(sizeof(u32) * 256, NULL);
416        if (fb_info == NULL)
417                goto error_nomem;
418
419        /* complete the abuse: */
420        fb_info->pseudo_palette = fb_info->par;
421        fb_info->par = info;
422
423        fb_info->screen_base = info->fb;
424
425        fb_info->fbops = &xenfb_fb_ops;
426        fb_info->var.xres_virtual = fb_info->var.xres = video[KPARAM_WIDTH];
427        fb_info->var.yres_virtual = fb_info->var.yres = video[KPARAM_HEIGHT];
428        fb_info->var.bits_per_pixel = XENFB_DEPTH;
429
430        fb_info->var.red = (struct fb_bitfield){16, 8, 0};
431        fb_info->var.green = (struct fb_bitfield){8, 8, 0};
432        fb_info->var.blue = (struct fb_bitfield){0, 8, 0};
433
434        fb_info->var.activate = FB_ACTIVATE_NOW;
435        fb_info->var.height = -1;
436        fb_info->var.width = -1;
437        fb_info->var.vmode = FB_VMODE_NONINTERLACED;
438
439        fb_info->fix.visual = FB_VISUAL_TRUECOLOR;
440        fb_info->fix.line_length = fb_info->var.xres * XENFB_DEPTH / 8;
441        fb_info->fix.smem_start = 0;
442        fb_info->fix.smem_len = fb_size;
443        strcpy(fb_info->fix.id, "xen");
444        fb_info->fix.type = FB_TYPE_PACKED_PIXELS;
445        fb_info->fix.accel = FB_ACCEL_NONE;
446
447        fb_info->flags = FBINFO_FLAG_DEFAULT | FBINFO_VIRTFB;
448
449        ret = fb_alloc_cmap(&fb_info->cmap, 256, 0);
450        if (ret < 0) {
451                framebuffer_release(fb_info);
452                xenbus_dev_fatal(dev, ret, "fb_alloc_cmap");
453                goto error;
454        }
455
456        fb_info->fbdefio = &xenfb_defio;
457        fb_deferred_io_init(fb_info);
458
459        xenfb_init_shared_page(info, fb_info);
460
461        ret = xenfb_connect_backend(dev, info);
462        if (ret < 0) {
463                xenbus_dev_fatal(dev, ret, "xenfb_connect_backend");
464                goto error_fb;
465        }
466
467        ret = register_framebuffer(fb_info);
468        if (ret) {
469                xenbus_dev_fatal(dev, ret, "register_framebuffer");
470                goto error_fb;
471        }
472        info->fb_info = fb_info;
473
474        xenfb_make_preferred_console();
475        return 0;
476
477error_fb:
478        fb_deferred_io_cleanup(fb_info);
479        fb_dealloc_cmap(&fb_info->cmap);
480        framebuffer_release(fb_info);
481error_nomem:
482        if (!ret) {
483                ret = -ENOMEM;
484                xenbus_dev_fatal(dev, ret, "allocating device memory");
485        }
486error:
487        xenfb_remove(dev);
488        return ret;
489}
490
491static void xenfb_make_preferred_console(void)
492{
493        struct console *c;
494
495        if (console_set_on_cmdline)
496                return;
497
498        console_lock();
499        for_each_console(c) {
500                if (!strcmp(c->name, "tty") && c->index == 0)
501                        break;
502        }
503        console_unlock();
504        if (c) {
505                unregister_console(c);
506                c->flags |= CON_CONSDEV;
507                c->flags &= ~CON_PRINTBUFFER; /* don't print again */
508                register_console(c);
509        }
510}
511
512static int xenfb_resume(struct xenbus_device *dev)
513{
514        struct xenfb_info *info = dev_get_drvdata(&dev->dev);
515
516        xenfb_disconnect_backend(info);
517        xenfb_init_shared_page(info, info->fb_info);
518        return xenfb_connect_backend(dev, info);
519}
520
521static int xenfb_remove(struct xenbus_device *dev)
522{
523        struct xenfb_info *info = dev_get_drvdata(&dev->dev);
524
525        xenfb_disconnect_backend(info);
526        if (info->fb_info) {
527                fb_deferred_io_cleanup(info->fb_info);
528                unregister_framebuffer(info->fb_info);
529                fb_dealloc_cmap(&info->fb_info->cmap);
530                framebuffer_release(info->fb_info);
531        }
532        free_page((unsigned long)info->page);
533        vfree(info->mfns);
534        vfree(info->fb);
535        kfree(info);
536
537        return 0;
538}
539
540static unsigned long vmalloc_to_mfn(void *address)
541{
542        return pfn_to_mfn(vmalloc_to_pfn(address));
543}
544
545static void xenfb_init_shared_page(struct xenfb_info *info,
546                                   struct fb_info *fb_info)
547{
548        int i;
549        int epd = PAGE_SIZE / sizeof(info->mfns[0]);
550
551        for (i = 0; i < info->nr_pages; i++)
552                info->mfns[i] = vmalloc_to_mfn(info->fb + i * PAGE_SIZE);
553
554        for (i = 0; i * epd < info->nr_pages; i++)
555                info->page->pd[i] = vmalloc_to_mfn(&info->mfns[i * epd]);
556
557        info->page->width = fb_info->var.xres;
558        info->page->height = fb_info->var.yres;
559        info->page->depth = fb_info->var.bits_per_pixel;
560        info->page->line_length = fb_info->fix.line_length;
561        info->page->mem_length = fb_info->fix.smem_len;
562        info->page->in_cons = info->page->in_prod = 0;
563        info->page->out_cons = info->page->out_prod = 0;
564}
565
566static int xenfb_connect_backend(struct xenbus_device *dev,
567                                 struct xenfb_info *info)
568{
569        int ret, evtchn, irq;
570        struct xenbus_transaction xbt;
571
572        ret = xenbus_alloc_evtchn(dev, &evtchn);
573        if (ret)
574                return ret;
575        irq = bind_evtchn_to_irqhandler(evtchn, xenfb_event_handler,
576                                        0, dev->devicetype, info);
577        if (irq < 0) {
578                xenbus_free_evtchn(dev, evtchn);
579                xenbus_dev_fatal(dev, ret, "bind_evtchn_to_irqhandler");
580                return irq;
581        }
582 again:
583        ret = xenbus_transaction_start(&xbt);
584        if (ret) {
585                xenbus_dev_fatal(dev, ret, "starting transaction");
586                goto unbind_irq;
587        }
588        ret = xenbus_printf(xbt, dev->nodename, "page-ref", "%lu",
589                            virt_to_mfn(info->page));
590        if (ret)
591                goto error_xenbus;
592        ret = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
593                            evtchn);
594        if (ret)
595                goto error_xenbus;
596        ret = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
597                            XEN_IO_PROTO_ABI_NATIVE);
598        if (ret)
599                goto error_xenbus;
600        ret = xenbus_printf(xbt, dev->nodename, "feature-update", "1");
601        if (ret)
602                goto error_xenbus;
603        ret = xenbus_transaction_end(xbt, 0);
604        if (ret) {
605                if (ret == -EAGAIN)
606                        goto again;
607                xenbus_dev_fatal(dev, ret, "completing transaction");
608                goto unbind_irq;
609        }
610
611        xenbus_switch_state(dev, XenbusStateInitialised);
612        info->irq = irq;
613        return 0;
614
615 error_xenbus:
616        xenbus_transaction_end(xbt, 1);
617        xenbus_dev_fatal(dev, ret, "writing xenstore");
618 unbind_irq:
619        unbind_from_irqhandler(irq, info);
620        return ret;
621}
622
623static void xenfb_disconnect_backend(struct xenfb_info *info)
624{
625        /* Prevent xenfb refresh */
626        info->update_wanted = 0;
627        if (info->irq >= 0)
628                unbind_from_irqhandler(info->irq, info);
629        info->irq = -1;
630}
631
632static void xenfb_backend_changed(struct xenbus_device *dev,
633                                  enum xenbus_state backend_state)
634{
635        struct xenfb_info *info = dev_get_drvdata(&dev->dev);
636        int val;
637
638        switch (backend_state) {
639        case XenbusStateInitialising:
640        case XenbusStateInitialised:
641        case XenbusStateReconfiguring:
642        case XenbusStateReconfigured:
643        case XenbusStateUnknown:
644                break;
645
646        case XenbusStateInitWait:
647                xenbus_switch_state(dev, XenbusStateConnected);
648                break;
649
650        case XenbusStateConnected:
651                /*
652                 * Work around xenbus race condition: If backend goes
653                 * through InitWait to Connected fast enough, we can
654                 * get Connected twice here.
655                 */
656                if (dev->state != XenbusStateConnected)
657                        /* no InitWait seen yet, fudge it */
658                        xenbus_switch_state(dev, XenbusStateConnected);
659
660                if (xenbus_scanf(XBT_NIL, info->xbdev->otherend,
661                                 "request-update", "%d", &val) < 0)
662                        val = 0;
663                if (val)
664                        info->update_wanted = 1;
665
666                if (xenbus_scanf(XBT_NIL, dev->otherend,
667                                 "feature-resize", "%d", &val) < 0)
668                        val = 0;
669                info->feature_resize = val;
670                break;
671
672        case XenbusStateClosed:
673                if (dev->state == XenbusStateClosed)
674                        break;
675                /* Missed the backend's CLOSING state -- fallthrough */
676        case XenbusStateClosing:
677                xenbus_frontend_closed(dev);
678                break;
679        }
680}
681
682static const struct xenbus_device_id xenfb_ids[] = {
683        { "vfb" },
684        { "" }
685};
686
687static struct xenbus_driver xenfb_driver = {
688        .ids = xenfb_ids,
689        .probe = xenfb_probe,
690        .remove = xenfb_remove,
691        .resume = xenfb_resume,
692        .otherend_changed = xenfb_backend_changed,
693};
694
695static int __init xenfb_init(void)
696{
697        if (!xen_domain())
698                return -ENODEV;
699
700        /* Nothing to do if running in dom0. */
701        if (xen_initial_domain())
702                return -ENODEV;
703
704        if (!xen_has_pv_devices())
705                return -ENODEV;
706
707        return xenbus_register_frontend(&xenfb_driver);
708}
709
710static void __exit xenfb_cleanup(void)
711{
712        xenbus_unregister_driver(&xenfb_driver);
713}
714
715module_init(xenfb_init);
716module_exit(xenfb_cleanup);
717
718MODULE_DESCRIPTION("Xen virtual framebuffer device frontend");
719MODULE_LICENSE("GPL");
720MODULE_ALIAS("xen:vfb");
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