/*
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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           *gfns;
        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 void 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 *pagereflist)
{
        struct xenfb_info *info = fb_info->par;
        struct fb_deferred_io_pageref *pageref;
        unsigned long beg, end;
        int y1, y2, miny, maxy;

        miny = INT_MAX;
        maxy = 0;
        list_for_each_entry(pageref, pagereflist, list) {
                beg = pageref->offset;
                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);
#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 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 void xenfb_defio_damage_range(struct fb_info *info, off_t off, size_t len)
{
        struct xenfb_info *xenfb_info = info->par;

        xenfb_refresh(xenfb_info, 0, 0, xenfb_info->page->width, xenfb_info->page->height);
}

static void xenfb_defio_damage_area(struct fb_info *info, u32 x, u32 y,
                                    u32 width, u32 height)
{
        struct xenfb_info *xenfb_info = info->par;

        xenfb_refresh(xenfb_info, x, y, width, height);
}

FB_GEN_DEFAULT_DEFERRED_SYSMEM_OPS(xenfb,
                                   xenfb_defio_damage_range,
                                   xenfb_defio_damage_area)

static const struct fb_ops xenfb_fb_ops = {
        .owner          = THIS_MODULE,
        FB_DEFAULT_DEFERRED_OPS(xenfb),
        .fb_setcolreg   = xenfb_setcolreg,
        .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_obj(*info);
        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;
        }

        video[KPARAM_WIDTH] = xenbus_read_unsigned(dev->otherend, "width",
                                                   video[KPARAM_WIDTH]);
        video[KPARAM_HEIGHT] = xenbus_read_unsigned(dev->otherend, "height",
                                                    video[KPARAM_HEIGHT]);

        /* 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) {
                pr_warn("display parameters %d,%d,%d invalid, use defaults\n",
                        video[KPARAM_MEM], video[KPARAM_WIDTH],
                        video[KPARAM_HEIGHT]);
                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->gfns = vmalloc_array(info->nr_pages, sizeof(unsigned long));
        if (!info->gfns)
                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->device = &dev->dev;

        fb_info->screen_buffer = 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_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_list_lock();
        for_each_console(c) {
                if (!strcmp(c->name, "tty") && c->index == 0)
                        break;
        }
        if (c)
                console_force_preferred_locked(c);
        console_list_unlock();
}

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 void 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->gfns);
        vfree(info->fb);
        kfree(info);
}

static unsigned long vmalloc_to_gfn(void *address)
{
        return xen_page_to_gfn(vmalloc_to_page(address));
}

static void xenfb_init_shared_page(struct xenfb_info *info,
                                   struct fb_info *fb_info)
{
        int i;
        int epd = PAGE_SIZE / sizeof(info->gfns[0]);

        for (i = 0; i < info->nr_pages; i++)
                info->gfns[i] = vmalloc_to_gfn(info->fb + i * PAGE_SIZE);

        for (i = 0; i * epd < info->nr_pages; i++)
                info->page->pd[i] = vmalloc_to_gfn(&info->gfns[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_gfn(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);

        switch (backend_state) {
        case XenbusStateInitialising:
        case XenbusStateInitialised:
        case XenbusStateReconfiguring:
        case XenbusStateReconfigured:
        case XenbusStateUnknown:
                break;

        case XenbusStateInitWait:
                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)
                        /* no InitWait seen yet, fudge it */
                        xenbus_switch_state(dev, XenbusStateConnected);

                if (xenbus_read_unsigned(info->xbdev->otherend,
                                         "request-update", 0))
                        info->update_wanted = 1;

                info->feature_resize = xenbus_read_unsigned(dev->otherend,
                                                        "feature-resize", 0);
                break;

        case XenbusStateClosed:
                if (dev->state == XenbusStateClosed)
                        break;
                fallthrough;    /* Missed the backend's CLOSING state */
        case XenbusStateClosing:
                xenbus_frontend_closed(dev);
                break;
        }
}

static const struct xenbus_device_id xenfb_ids[] = {
        { "vfb" },
        { "" }
};

static struct xenbus_driver xenfb_driver = {
        .ids = xenfb_ids,
        .probe = xenfb_probe,
        .remove = xenfb_remove,
        .resume = xenfb_resume,
        .otherend_changed = xenfb_backend_changed,
        .not_essential = true,
};

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");