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0001 /*
0002  * Xen para-virtual frame buffer device
0003  *
0004  * Copyright (C) 2005-2006 Anthony Liguori <aliguori@us.ibm.com>
0005  * Copyright (C) 2006-2008 Red Hat, Inc., Markus Armbruster <armbru@redhat.com>
0006  *
0007  *  Based on linux/drivers/video/q40fb.c
0008  *
0009  *  This file is subject to the terms and conditions of the GNU General Public
0010  *  License. See the file COPYING in the main directory of this archive for
0011  *  more details.
0012  */
0013 
0014 /*
0015  * TODO:
0016  *
0017  * Switch to grant tables when they become capable of dealing with the
0018  * frame buffer.
0019  */
0020 
0021 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0022 
0023 #include <linux/console.h>
0024 #include <linux/kernel.h>
0025 #include <linux/errno.h>
0026 #include <linux/fb.h>
0027 #include <linux/module.h>
0028 #include <linux/slab.h>
0029 #include <linux/vmalloc.h>
0030 #include <linux/mm.h>
0031 
0032 #include <asm/xen/hypervisor.h>
0033 
0034 #include <xen/xen.h>
0035 #include <xen/events.h>
0036 #include <xen/page.h>
0037 #include <xen/interface/io/fbif.h>
0038 #include <xen/interface/io/protocols.h>
0039 #include <xen/xenbus.h>
0040 #include <xen/platform_pci.h>
0041 
0042 struct xenfb_info {
0043     unsigned char       *fb;
0044     struct fb_info      *fb_info;
0045     int         x1, y1, x2, y2; /* dirty rectangle,
0046                            protected by dirty_lock */
0047     spinlock_t      dirty_lock;
0048     int         nr_pages;
0049     int         irq;
0050     struct xenfb_page   *page;
0051     unsigned long       *gfns;
0052     int         update_wanted; /* XENFB_TYPE_UPDATE wanted */
0053     int         feature_resize; /* XENFB_TYPE_RESIZE ok */
0054     struct xenfb_resize resize;     /* protected by resize_lock */
0055     int         resize_dpy; /* ditto */
0056     spinlock_t      resize_lock;
0057 
0058     struct xenbus_device    *xbdev;
0059 };
0060 
0061 #define XENFB_DEFAULT_FB_LEN (XENFB_WIDTH * XENFB_HEIGHT * XENFB_DEPTH / 8)
0062 
0063 enum { KPARAM_MEM, KPARAM_WIDTH, KPARAM_HEIGHT, KPARAM_CNT };
0064 static int video[KPARAM_CNT] = { 2, XENFB_WIDTH, XENFB_HEIGHT };
0065 module_param_array(video, int, NULL, 0);
0066 MODULE_PARM_DESC(video,
0067     "Video memory size in MB, width, height in pixels (default 2,800,600)");
0068 
0069 static void xenfb_make_preferred_console(void);
0070 static int xenfb_remove(struct xenbus_device *);
0071 static void xenfb_init_shared_page(struct xenfb_info *, struct fb_info *);
0072 static int xenfb_connect_backend(struct xenbus_device *, struct xenfb_info *);
0073 static void xenfb_disconnect_backend(struct xenfb_info *);
0074 
0075 static void xenfb_send_event(struct xenfb_info *info,
0076                  union xenfb_out_event *event)
0077 {
0078     u32 prod;
0079 
0080     prod = info->page->out_prod;
0081     /* caller ensures !xenfb_queue_full() */
0082     mb();           /* ensure ring space available */
0083     XENFB_OUT_RING_REF(info->page, prod) = *event;
0084     wmb();          /* ensure ring contents visible */
0085     info->page->out_prod = prod + 1;
0086 
0087     notify_remote_via_irq(info->irq);
0088 }
0089 
0090 static void xenfb_do_update(struct xenfb_info *info,
0091                 int x, int y, int w, int h)
0092 {
0093     union xenfb_out_event event;
0094 
0095     memset(&event, 0, sizeof(event));
0096     event.type = XENFB_TYPE_UPDATE;
0097     event.update.x = x;
0098     event.update.y = y;
0099     event.update.width = w;
0100     event.update.height = h;
0101 
0102     /* caller ensures !xenfb_queue_full() */
0103     xenfb_send_event(info, &event);
0104 }
0105 
0106 static void xenfb_do_resize(struct xenfb_info *info)
0107 {
0108     union xenfb_out_event event;
0109 
0110     memset(&event, 0, sizeof(event));
0111     event.resize = info->resize;
0112 
0113     /* caller ensures !xenfb_queue_full() */
0114     xenfb_send_event(info, &event);
0115 }
0116 
0117 static int xenfb_queue_full(struct xenfb_info *info)
0118 {
0119     u32 cons, prod;
0120 
0121     prod = info->page->out_prod;
0122     cons = info->page->out_cons;
0123     return prod - cons == XENFB_OUT_RING_LEN;
0124 }
0125 
0126 static void xenfb_handle_resize_dpy(struct xenfb_info *info)
0127 {
0128     unsigned long flags;
0129 
0130     spin_lock_irqsave(&info->resize_lock, flags);
0131     if (info->resize_dpy) {
0132         if (!xenfb_queue_full(info)) {
0133             info->resize_dpy = 0;
0134             xenfb_do_resize(info);
0135         }
0136     }
0137     spin_unlock_irqrestore(&info->resize_lock, flags);
0138 }
0139 
0140 static void xenfb_refresh(struct xenfb_info *info,
0141               int x1, int y1, int w, int h)
0142 {
0143     unsigned long flags;
0144     int x2 = x1 + w - 1;
0145     int y2 = y1 + h - 1;
0146 
0147     xenfb_handle_resize_dpy(info);
0148 
0149     if (!info->update_wanted)
0150         return;
0151 
0152     spin_lock_irqsave(&info->dirty_lock, flags);
0153 
0154     /* Combine with dirty rectangle: */
0155     if (info->y1 < y1)
0156         y1 = info->y1;
0157     if (info->y2 > y2)
0158         y2 = info->y2;
0159     if (info->x1 < x1)
0160         x1 = info->x1;
0161     if (info->x2 > x2)
0162         x2 = info->x2;
0163 
0164     if (xenfb_queue_full(info)) {
0165         /* Can't send right now, stash it in the dirty rectangle */
0166         info->x1 = x1;
0167         info->x2 = x2;
0168         info->y1 = y1;
0169         info->y2 = y2;
0170         spin_unlock_irqrestore(&info->dirty_lock, flags);
0171         return;
0172     }
0173 
0174     /* Clear dirty rectangle: */
0175     info->x1 = info->y1 = INT_MAX;
0176     info->x2 = info->y2 = 0;
0177 
0178     spin_unlock_irqrestore(&info->dirty_lock, flags);
0179 
0180     if (x1 <= x2 && y1 <= y2)
0181         xenfb_do_update(info, x1, y1, x2 - x1 + 1, y2 - y1 + 1);
0182 }
0183 
0184 static void xenfb_deferred_io(struct fb_info *fb_info, struct list_head *pagereflist)
0185 {
0186     struct xenfb_info *info = fb_info->par;
0187     struct fb_deferred_io_pageref *pageref;
0188     unsigned long beg, end;
0189     int y1, y2, miny, maxy;
0190 
0191     miny = INT_MAX;
0192     maxy = 0;
0193     list_for_each_entry(pageref, pagereflist, list) {
0194         beg = pageref->offset;
0195         end = beg + PAGE_SIZE - 1;
0196         y1 = beg / fb_info->fix.line_length;
0197         y2 = end / fb_info->fix.line_length;
0198         if (y2 >= fb_info->var.yres)
0199             y2 = fb_info->var.yres - 1;
0200         if (miny > y1)
0201             miny = y1;
0202         if (maxy < y2)
0203             maxy = y2;
0204     }
0205     xenfb_refresh(info, 0, miny, fb_info->var.xres, maxy - miny + 1);
0206 }
0207 
0208 static struct fb_deferred_io xenfb_defio = {
0209     .delay      = HZ / 20,
0210     .deferred_io    = xenfb_deferred_io,
0211 };
0212 
0213 static int xenfb_setcolreg(unsigned regno, unsigned red, unsigned green,
0214                unsigned blue, unsigned transp,
0215                struct fb_info *info)
0216 {
0217     u32 v;
0218 
0219     if (regno > info->cmap.len)
0220         return 1;
0221 
0222 #define CNVT_TOHW(val, width) ((((val)<<(width))+0x7FFF-(val))>>16)
0223     red = CNVT_TOHW(red, info->var.red.length);
0224     green = CNVT_TOHW(green, info->var.green.length);
0225     blue = CNVT_TOHW(blue, info->var.blue.length);
0226 #undef CNVT_TOHW
0227 
0228     v = (red << info->var.red.offset) |
0229         (green << info->var.green.offset) |
0230         (blue << info->var.blue.offset);
0231 
0232     switch (info->var.bits_per_pixel) {
0233     case 16:
0234     case 24:
0235     case 32:
0236         ((u32 *)info->pseudo_palette)[regno] = v;
0237         break;
0238     }
0239 
0240     return 0;
0241 }
0242 
0243 static void xenfb_fillrect(struct fb_info *p, const struct fb_fillrect *rect)
0244 {
0245     struct xenfb_info *info = p->par;
0246 
0247     sys_fillrect(p, rect);
0248     xenfb_refresh(info, rect->dx, rect->dy, rect->width, rect->height);
0249 }
0250 
0251 static void xenfb_imageblit(struct fb_info *p, const struct fb_image *image)
0252 {
0253     struct xenfb_info *info = p->par;
0254 
0255     sys_imageblit(p, image);
0256     xenfb_refresh(info, image->dx, image->dy, image->width, image->height);
0257 }
0258 
0259 static void xenfb_copyarea(struct fb_info *p, const struct fb_copyarea *area)
0260 {
0261     struct xenfb_info *info = p->par;
0262 
0263     sys_copyarea(p, area);
0264     xenfb_refresh(info, area->dx, area->dy, area->width, area->height);
0265 }
0266 
0267 static ssize_t xenfb_write(struct fb_info *p, const char __user *buf,
0268             size_t count, loff_t *ppos)
0269 {
0270     struct xenfb_info *info = p->par;
0271     ssize_t res;
0272 
0273     res = fb_sys_write(p, buf, count, ppos);
0274     xenfb_refresh(info, 0, 0, info->page->width, info->page->height);
0275     return res;
0276 }
0277 
0278 static int
0279 xenfb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
0280 {
0281     struct xenfb_info *xenfb_info;
0282     int required_mem_len;
0283 
0284     xenfb_info = info->par;
0285 
0286     if (!xenfb_info->feature_resize) {
0287         if (var->xres == video[KPARAM_WIDTH] &&
0288             var->yres == video[KPARAM_HEIGHT] &&
0289             var->bits_per_pixel == xenfb_info->page->depth) {
0290             return 0;
0291         }
0292         return -EINVAL;
0293     }
0294 
0295     /* Can't resize past initial width and height */
0296     if (var->xres > video[KPARAM_WIDTH] || var->yres > video[KPARAM_HEIGHT])
0297         return -EINVAL;
0298 
0299     required_mem_len = var->xres * var->yres * xenfb_info->page->depth / 8;
0300     if (var->bits_per_pixel == xenfb_info->page->depth &&
0301         var->xres <= info->fix.line_length / (XENFB_DEPTH / 8) &&
0302         required_mem_len <= info->fix.smem_len) {
0303         var->xres_virtual = var->xres;
0304         var->yres_virtual = var->yres;
0305         return 0;
0306     }
0307     return -EINVAL;
0308 }
0309 
0310 static int xenfb_set_par(struct fb_info *info)
0311 {
0312     struct xenfb_info *xenfb_info;
0313     unsigned long flags;
0314 
0315     xenfb_info = info->par;
0316 
0317     spin_lock_irqsave(&xenfb_info->resize_lock, flags);
0318     xenfb_info->resize.type = XENFB_TYPE_RESIZE;
0319     xenfb_info->resize.width = info->var.xres;
0320     xenfb_info->resize.height = info->var.yres;
0321     xenfb_info->resize.stride = info->fix.line_length;
0322     xenfb_info->resize.depth = info->var.bits_per_pixel;
0323     xenfb_info->resize.offset = 0;
0324     xenfb_info->resize_dpy = 1;
0325     spin_unlock_irqrestore(&xenfb_info->resize_lock, flags);
0326     return 0;
0327 }
0328 
0329 static const struct fb_ops xenfb_fb_ops = {
0330     .owner      = THIS_MODULE,
0331     .fb_read    = fb_sys_read,
0332     .fb_write   = xenfb_write,
0333     .fb_setcolreg   = xenfb_setcolreg,
0334     .fb_fillrect    = xenfb_fillrect,
0335     .fb_copyarea    = xenfb_copyarea,
0336     .fb_imageblit   = xenfb_imageblit,
0337     .fb_check_var   = xenfb_check_var,
0338     .fb_set_par     = xenfb_set_par,
0339     .fb_mmap    = fb_deferred_io_mmap,
0340 };
0341 
0342 static irqreturn_t xenfb_event_handler(int rq, void *dev_id)
0343 {
0344     /*
0345      * No in events recognized, simply ignore them all.
0346      * If you need to recognize some, see xen-kbdfront's
0347      * input_handler() for how to do that.
0348      */
0349     struct xenfb_info *info = dev_id;
0350     struct xenfb_page *page = info->page;
0351 
0352     if (page->in_cons != page->in_prod) {
0353         info->page->in_cons = info->page->in_prod;
0354         notify_remote_via_irq(info->irq);
0355     }
0356 
0357     /* Flush dirty rectangle: */
0358     xenfb_refresh(info, INT_MAX, INT_MAX, -INT_MAX, -INT_MAX);
0359 
0360     return IRQ_HANDLED;
0361 }
0362 
0363 static int xenfb_probe(struct xenbus_device *dev,
0364                const struct xenbus_device_id *id)
0365 {
0366     struct xenfb_info *info;
0367     struct fb_info *fb_info;
0368     int fb_size;
0369     int val;
0370     int ret = 0;
0371 
0372     info = kzalloc(sizeof(*info), GFP_KERNEL);
0373     if (info == NULL) {
0374         xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
0375         return -ENOMEM;
0376     }
0377 
0378     /* Limit kernel param videoram amount to what is in xenstore */
0379     if (xenbus_scanf(XBT_NIL, dev->otherend, "videoram", "%d", &val) == 1) {
0380         if (val < video[KPARAM_MEM])
0381             video[KPARAM_MEM] = val;
0382     }
0383 
0384     video[KPARAM_WIDTH] = xenbus_read_unsigned(dev->otherend, "width",
0385                            video[KPARAM_WIDTH]);
0386     video[KPARAM_HEIGHT] = xenbus_read_unsigned(dev->otherend, "height",
0387                             video[KPARAM_HEIGHT]);
0388 
0389     /* If requested res does not fit in available memory, use default */
0390     fb_size = video[KPARAM_MEM] * 1024 * 1024;
0391     if (video[KPARAM_WIDTH] * video[KPARAM_HEIGHT] * XENFB_DEPTH / 8
0392         > fb_size) {
0393         pr_warn("display parameters %d,%d,%d invalid, use defaults\n",
0394             video[KPARAM_MEM], video[KPARAM_WIDTH],
0395             video[KPARAM_HEIGHT]);
0396         video[KPARAM_WIDTH] = XENFB_WIDTH;
0397         video[KPARAM_HEIGHT] = XENFB_HEIGHT;
0398         fb_size = XENFB_DEFAULT_FB_LEN;
0399     }
0400 
0401     dev_set_drvdata(&dev->dev, info);
0402     info->xbdev = dev;
0403     info->irq = -1;
0404     info->x1 = info->y1 = INT_MAX;
0405     spin_lock_init(&info->dirty_lock);
0406     spin_lock_init(&info->resize_lock);
0407 
0408     info->fb = vzalloc(fb_size);
0409     if (info->fb == NULL)
0410         goto error_nomem;
0411 
0412     info->nr_pages = (fb_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
0413 
0414     info->gfns = vmalloc(array_size(sizeof(unsigned long), info->nr_pages));
0415     if (!info->gfns)
0416         goto error_nomem;
0417 
0418     /* set up shared page */
0419     info->page = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
0420     if (!info->page)
0421         goto error_nomem;
0422 
0423     /* abusing framebuffer_alloc() to allocate pseudo_palette */
0424     fb_info = framebuffer_alloc(sizeof(u32) * 256, NULL);
0425     if (fb_info == NULL)
0426         goto error_nomem;
0427 
0428     /* complete the abuse: */
0429     fb_info->pseudo_palette = fb_info->par;
0430     fb_info->par = info;
0431 
0432     fb_info->screen_base = info->fb;
0433 
0434     fb_info->fbops = &xenfb_fb_ops;
0435     fb_info->var.xres_virtual = fb_info->var.xres = video[KPARAM_WIDTH];
0436     fb_info->var.yres_virtual = fb_info->var.yres = video[KPARAM_HEIGHT];
0437     fb_info->var.bits_per_pixel = XENFB_DEPTH;
0438 
0439     fb_info->var.red = (struct fb_bitfield){16, 8, 0};
0440     fb_info->var.green = (struct fb_bitfield){8, 8, 0};
0441     fb_info->var.blue = (struct fb_bitfield){0, 8, 0};
0442 
0443     fb_info->var.activate = FB_ACTIVATE_NOW;
0444     fb_info->var.height = -1;
0445     fb_info->var.width = -1;
0446     fb_info->var.vmode = FB_VMODE_NONINTERLACED;
0447 
0448     fb_info->fix.visual = FB_VISUAL_TRUECOLOR;
0449     fb_info->fix.line_length = fb_info->var.xres * XENFB_DEPTH / 8;
0450     fb_info->fix.smem_start = 0;
0451     fb_info->fix.smem_len = fb_size;
0452     strcpy(fb_info->fix.id, "xen");
0453     fb_info->fix.type = FB_TYPE_PACKED_PIXELS;
0454     fb_info->fix.accel = FB_ACCEL_NONE;
0455 
0456     fb_info->flags = FBINFO_FLAG_DEFAULT | FBINFO_VIRTFB;
0457 
0458     ret = fb_alloc_cmap(&fb_info->cmap, 256, 0);
0459     if (ret < 0) {
0460         framebuffer_release(fb_info);
0461         xenbus_dev_fatal(dev, ret, "fb_alloc_cmap");
0462         goto error;
0463     }
0464 
0465     fb_info->fbdefio = &xenfb_defio;
0466     fb_deferred_io_init(fb_info);
0467 
0468     xenfb_init_shared_page(info, fb_info);
0469 
0470     ret = xenfb_connect_backend(dev, info);
0471     if (ret < 0) {
0472         xenbus_dev_fatal(dev, ret, "xenfb_connect_backend");
0473         goto error_fb;
0474     }
0475 
0476     ret = register_framebuffer(fb_info);
0477     if (ret) {
0478         xenbus_dev_fatal(dev, ret, "register_framebuffer");
0479         goto error_fb;
0480     }
0481     info->fb_info = fb_info;
0482 
0483     xenfb_make_preferred_console();
0484     return 0;
0485 
0486 error_fb:
0487     fb_deferred_io_cleanup(fb_info);
0488     fb_dealloc_cmap(&fb_info->cmap);
0489     framebuffer_release(fb_info);
0490 error_nomem:
0491     if (!ret) {
0492         ret = -ENOMEM;
0493         xenbus_dev_fatal(dev, ret, "allocating device memory");
0494     }
0495 error:
0496     xenfb_remove(dev);
0497     return ret;
0498 }
0499 
0500 static void xenfb_make_preferred_console(void)
0501 {
0502     struct console *c;
0503 
0504     if (console_set_on_cmdline)
0505         return;
0506 
0507     console_lock();
0508     for_each_console(c) {
0509         if (!strcmp(c->name, "tty") && c->index == 0)
0510             break;
0511     }
0512     console_unlock();
0513     if (c) {
0514         unregister_console(c);
0515         c->flags |= CON_CONSDEV;
0516         c->flags &= ~CON_PRINTBUFFER; /* don't print again */
0517         register_console(c);
0518     }
0519 }
0520 
0521 static int xenfb_resume(struct xenbus_device *dev)
0522 {
0523     struct xenfb_info *info = dev_get_drvdata(&dev->dev);
0524 
0525     xenfb_disconnect_backend(info);
0526     xenfb_init_shared_page(info, info->fb_info);
0527     return xenfb_connect_backend(dev, info);
0528 }
0529 
0530 static int xenfb_remove(struct xenbus_device *dev)
0531 {
0532     struct xenfb_info *info = dev_get_drvdata(&dev->dev);
0533 
0534     xenfb_disconnect_backend(info);
0535     if (info->fb_info) {
0536         fb_deferred_io_cleanup(info->fb_info);
0537         unregister_framebuffer(info->fb_info);
0538         fb_dealloc_cmap(&info->fb_info->cmap);
0539         framebuffer_release(info->fb_info);
0540     }
0541     free_page((unsigned long)info->page);
0542     vfree(info->gfns);
0543     vfree(info->fb);
0544     kfree(info);
0545 
0546     return 0;
0547 }
0548 
0549 static unsigned long vmalloc_to_gfn(void *address)
0550 {
0551     return xen_page_to_gfn(vmalloc_to_page(address));
0552 }
0553 
0554 static void xenfb_init_shared_page(struct xenfb_info *info,
0555                    struct fb_info *fb_info)
0556 {
0557     int i;
0558     int epd = PAGE_SIZE / sizeof(info->gfns[0]);
0559 
0560     for (i = 0; i < info->nr_pages; i++)
0561         info->gfns[i] = vmalloc_to_gfn(info->fb + i * PAGE_SIZE);
0562 
0563     for (i = 0; i * epd < info->nr_pages; i++)
0564         info->page->pd[i] = vmalloc_to_gfn(&info->gfns[i * epd]);
0565 
0566     info->page->width = fb_info->var.xres;
0567     info->page->height = fb_info->var.yres;
0568     info->page->depth = fb_info->var.bits_per_pixel;
0569     info->page->line_length = fb_info->fix.line_length;
0570     info->page->mem_length = fb_info->fix.smem_len;
0571     info->page->in_cons = info->page->in_prod = 0;
0572     info->page->out_cons = info->page->out_prod = 0;
0573 }
0574 
0575 static int xenfb_connect_backend(struct xenbus_device *dev,
0576                  struct xenfb_info *info)
0577 {
0578     int ret, evtchn, irq;
0579     struct xenbus_transaction xbt;
0580 
0581     ret = xenbus_alloc_evtchn(dev, &evtchn);
0582     if (ret)
0583         return ret;
0584     irq = bind_evtchn_to_irqhandler(evtchn, xenfb_event_handler,
0585                     0, dev->devicetype, info);
0586     if (irq < 0) {
0587         xenbus_free_evtchn(dev, evtchn);
0588         xenbus_dev_fatal(dev, ret, "bind_evtchn_to_irqhandler");
0589         return irq;
0590     }
0591  again:
0592     ret = xenbus_transaction_start(&xbt);
0593     if (ret) {
0594         xenbus_dev_fatal(dev, ret, "starting transaction");
0595         goto unbind_irq;
0596     }
0597     ret = xenbus_printf(xbt, dev->nodename, "page-ref", "%lu",
0598                 virt_to_gfn(info->page));
0599     if (ret)
0600         goto error_xenbus;
0601     ret = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
0602                 evtchn);
0603     if (ret)
0604         goto error_xenbus;
0605     ret = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
0606                 XEN_IO_PROTO_ABI_NATIVE);
0607     if (ret)
0608         goto error_xenbus;
0609     ret = xenbus_printf(xbt, dev->nodename, "feature-update", "1");
0610     if (ret)
0611         goto error_xenbus;
0612     ret = xenbus_transaction_end(xbt, 0);
0613     if (ret) {
0614         if (ret == -EAGAIN)
0615             goto again;
0616         xenbus_dev_fatal(dev, ret, "completing transaction");
0617         goto unbind_irq;
0618     }
0619 
0620     xenbus_switch_state(dev, XenbusStateInitialised);
0621     info->irq = irq;
0622     return 0;
0623 
0624  error_xenbus:
0625     xenbus_transaction_end(xbt, 1);
0626     xenbus_dev_fatal(dev, ret, "writing xenstore");
0627  unbind_irq:
0628     unbind_from_irqhandler(irq, info);
0629     return ret;
0630 }
0631 
0632 static void xenfb_disconnect_backend(struct xenfb_info *info)
0633 {
0634     /* Prevent xenfb refresh */
0635     info->update_wanted = 0;
0636     if (info->irq >= 0)
0637         unbind_from_irqhandler(info->irq, info);
0638     info->irq = -1;
0639 }
0640 
0641 static void xenfb_backend_changed(struct xenbus_device *dev,
0642                   enum xenbus_state backend_state)
0643 {
0644     struct xenfb_info *info = dev_get_drvdata(&dev->dev);
0645 
0646     switch (backend_state) {
0647     case XenbusStateInitialising:
0648     case XenbusStateInitialised:
0649     case XenbusStateReconfiguring:
0650     case XenbusStateReconfigured:
0651     case XenbusStateUnknown:
0652         break;
0653 
0654     case XenbusStateInitWait:
0655         xenbus_switch_state(dev, XenbusStateConnected);
0656         break;
0657 
0658     case XenbusStateConnected:
0659         /*
0660          * Work around xenbus race condition: If backend goes
0661          * through InitWait to Connected fast enough, we can
0662          * get Connected twice here.
0663          */
0664         if (dev->state != XenbusStateConnected)
0665             /* no InitWait seen yet, fudge it */
0666             xenbus_switch_state(dev, XenbusStateConnected);
0667 
0668         if (xenbus_read_unsigned(info->xbdev->otherend,
0669                      "request-update", 0))
0670             info->update_wanted = 1;
0671 
0672         info->feature_resize = xenbus_read_unsigned(dev->otherend,
0673                             "feature-resize", 0);
0674         break;
0675 
0676     case XenbusStateClosed:
0677         if (dev->state == XenbusStateClosed)
0678             break;
0679         fallthrough;    /* Missed the backend's CLOSING state */
0680     case XenbusStateClosing:
0681         xenbus_frontend_closed(dev);
0682         break;
0683     }
0684 }
0685 
0686 static const struct xenbus_device_id xenfb_ids[] = {
0687     { "vfb" },
0688     { "" }
0689 };
0690 
0691 static struct xenbus_driver xenfb_driver = {
0692     .ids = xenfb_ids,
0693     .probe = xenfb_probe,
0694     .remove = xenfb_remove,
0695     .resume = xenfb_resume,
0696     .otherend_changed = xenfb_backend_changed,
0697     .not_essential = true,
0698 };
0699 
0700 static int __init xenfb_init(void)
0701 {
0702     if (!xen_domain())
0703         return -ENODEV;
0704 
0705     /* Nothing to do if running in dom0. */
0706     if (xen_initial_domain())
0707         return -ENODEV;
0708 
0709     if (!xen_has_pv_devices())
0710         return -ENODEV;
0711 
0712     return xenbus_register_frontend(&xenfb_driver);
0713 }
0714 
0715 static void __exit xenfb_cleanup(void)
0716 {
0717     xenbus_unregister_driver(&xenfb_driver);
0718 }
0719 
0720 module_init(xenfb_init);
0721 module_exit(xenfb_cleanup);
0722 
0723 MODULE_DESCRIPTION("Xen virtual framebuffer device frontend");
0724 MODULE_LICENSE("GPL");
0725 MODULE_ALIAS("xen:vfb");