blob: aab79c5e34c26ec99e20f7201ad38b33d76663ed [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0 OR MIT
/*
* Xen para-virtual DRM device
*
* Copyright (C) 2016-2018 EPAM Systems Inc.
*
* Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
*/
#include <linux/delay.h>
#include <linux/dma-mapping.h>
#include <linux/module.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_drv.h>
#include <drm/drm_ioctl.h>
#include <drm/drm_probe_helper.h>
#include <drm/drm_file.h>
#include <drm/drm_gem.h>
#include <xen/platform_pci.h>
#include <xen/xen.h>
#include <xen/xenbus.h>
#include <xen/xen-front-pgdir-shbuf.h>
#include <xen/interface/io/displif.h>
#include "xen_drm_front.h"
#include "xen_drm_front_cfg.h"
#include "xen_drm_front_evtchnl.h"
#include "xen_drm_front_gem.h"
#include "xen_drm_front_kms.h"
struct xen_drm_front_dbuf {
struct list_head list;
u64 dbuf_cookie;
u64 fb_cookie;
struct xen_front_pgdir_shbuf shbuf;
};
static void dbuf_add_to_list(struct xen_drm_front_info *front_info,
struct xen_drm_front_dbuf *dbuf, u64 dbuf_cookie)
{
dbuf->dbuf_cookie = dbuf_cookie;
list_add(&dbuf->list, &front_info->dbuf_list);
}
static struct xen_drm_front_dbuf *dbuf_get(struct list_head *dbuf_list,
u64 dbuf_cookie)
{
struct xen_drm_front_dbuf *buf, *q;
list_for_each_entry_safe(buf, q, dbuf_list, list)
if (buf->dbuf_cookie == dbuf_cookie)
return buf;
return NULL;
}
static void dbuf_free(struct list_head *dbuf_list, u64 dbuf_cookie)
{
struct xen_drm_front_dbuf *buf, *q;
list_for_each_entry_safe(buf, q, dbuf_list, list)
if (buf->dbuf_cookie == dbuf_cookie) {
list_del(&buf->list);
xen_front_pgdir_shbuf_unmap(&buf->shbuf);
xen_front_pgdir_shbuf_free(&buf->shbuf);
kfree(buf);
break;
}
}
static void dbuf_free_all(struct list_head *dbuf_list)
{
struct xen_drm_front_dbuf *buf, *q;
list_for_each_entry_safe(buf, q, dbuf_list, list) {
list_del(&buf->list);
xen_front_pgdir_shbuf_unmap(&buf->shbuf);
xen_front_pgdir_shbuf_free(&buf->shbuf);
kfree(buf);
}
}
static struct xendispl_req *
be_prepare_req(struct xen_drm_front_evtchnl *evtchnl, u8 operation)
{
struct xendispl_req *req;
req = RING_GET_REQUEST(&evtchnl->u.req.ring,
evtchnl->u.req.ring.req_prod_pvt);
req->operation = operation;
req->id = evtchnl->evt_next_id++;
evtchnl->evt_id = req->id;
return req;
}
static int be_stream_do_io(struct xen_drm_front_evtchnl *evtchnl,
struct xendispl_req *req)
{
reinit_completion(&evtchnl->u.req.completion);
if (unlikely(evtchnl->state != EVTCHNL_STATE_CONNECTED))
return -EIO;
xen_drm_front_evtchnl_flush(evtchnl);
return 0;
}
static int be_stream_wait_io(struct xen_drm_front_evtchnl *evtchnl)
{
if (wait_for_completion_timeout(&evtchnl->u.req.completion,
msecs_to_jiffies(XEN_DRM_FRONT_WAIT_BACK_MS)) <= 0)
return -ETIMEDOUT;
return evtchnl->u.req.resp_status;
}
int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
u32 x, u32 y, u32 width, u32 height,
u32 bpp, u64 fb_cookie)
{
struct xen_drm_front_evtchnl *evtchnl;
struct xen_drm_front_info *front_info;
struct xendispl_req *req;
unsigned long flags;
int ret;
front_info = pipeline->drm_info->front_info;
evtchnl = &front_info->evt_pairs[pipeline->index].req;
if (unlikely(!evtchnl))
return -EIO;
mutex_lock(&evtchnl->u.req.req_io_lock);
spin_lock_irqsave(&front_info->io_lock, flags);
req = be_prepare_req(evtchnl, XENDISPL_OP_SET_CONFIG);
req->op.set_config.x = x;
req->op.set_config.y = y;
req->op.set_config.width = width;
req->op.set_config.height = height;
req->op.set_config.bpp = bpp;
req->op.set_config.fb_cookie = fb_cookie;
ret = be_stream_do_io(evtchnl, req);
spin_unlock_irqrestore(&front_info->io_lock, flags);
if (ret == 0)
ret = be_stream_wait_io(evtchnl);
mutex_unlock(&evtchnl->u.req.req_io_lock);
return ret;
}
int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
u64 dbuf_cookie, u32 width, u32 height,
u32 bpp, u64 size, u32 offset,
struct page **pages)
{
struct xen_drm_front_evtchnl *evtchnl;
struct xen_drm_front_dbuf *dbuf;
struct xendispl_req *req;
struct xen_front_pgdir_shbuf_cfg buf_cfg;
unsigned long flags;
int ret;
evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
if (unlikely(!evtchnl))
return -EIO;
dbuf = kzalloc(sizeof(*dbuf), GFP_KERNEL);
if (!dbuf)
return -ENOMEM;
dbuf_add_to_list(front_info, dbuf, dbuf_cookie);
memset(&buf_cfg, 0, sizeof(buf_cfg));
buf_cfg.xb_dev = front_info->xb_dev;
buf_cfg.num_pages = DIV_ROUND_UP(size, PAGE_SIZE);
buf_cfg.pages = pages;
buf_cfg.pgdir = &dbuf->shbuf;
buf_cfg.be_alloc = front_info->cfg.be_alloc;
ret = xen_front_pgdir_shbuf_alloc(&buf_cfg);
if (ret < 0)
goto fail_shbuf_alloc;
mutex_lock(&evtchnl->u.req.req_io_lock);
spin_lock_irqsave(&front_info->io_lock, flags);
req = be_prepare_req(evtchnl, XENDISPL_OP_DBUF_CREATE);
req->op.dbuf_create.gref_directory =
xen_front_pgdir_shbuf_get_dir_start(&dbuf->shbuf);
req->op.dbuf_create.buffer_sz = size;
req->op.dbuf_create.data_ofs = offset;
req->op.dbuf_create.dbuf_cookie = dbuf_cookie;
req->op.dbuf_create.width = width;
req->op.dbuf_create.height = height;
req->op.dbuf_create.bpp = bpp;
if (buf_cfg.be_alloc)
req->op.dbuf_create.flags |= XENDISPL_DBUF_FLG_REQ_ALLOC;
ret = be_stream_do_io(evtchnl, req);
spin_unlock_irqrestore(&front_info->io_lock, flags);
if (ret < 0)
goto fail;
ret = be_stream_wait_io(evtchnl);
if (ret < 0)
goto fail;
ret = xen_front_pgdir_shbuf_map(&dbuf->shbuf);
if (ret < 0)
goto fail;
mutex_unlock(&evtchnl->u.req.req_io_lock);
return 0;
fail:
mutex_unlock(&evtchnl->u.req.req_io_lock);
fail_shbuf_alloc:
dbuf_free(&front_info->dbuf_list, dbuf_cookie);
return ret;
}
static int xen_drm_front_dbuf_destroy(struct xen_drm_front_info *front_info,
u64 dbuf_cookie)
{
struct xen_drm_front_evtchnl *evtchnl;
struct xendispl_req *req;
unsigned long flags;
bool be_alloc;
int ret;
evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
if (unlikely(!evtchnl))
return -EIO;
be_alloc = front_info->cfg.be_alloc;
/*
* For the backend allocated buffer release references now, so backend
* can free the buffer.
*/
if (be_alloc)
dbuf_free(&front_info->dbuf_list, dbuf_cookie);
mutex_lock(&evtchnl->u.req.req_io_lock);
spin_lock_irqsave(&front_info->io_lock, flags);
req = be_prepare_req(evtchnl, XENDISPL_OP_DBUF_DESTROY);
req->op.dbuf_destroy.dbuf_cookie = dbuf_cookie;
ret = be_stream_do_io(evtchnl, req);
spin_unlock_irqrestore(&front_info->io_lock, flags);
if (ret == 0)
ret = be_stream_wait_io(evtchnl);
/*
* Do this regardless of communication status with the backend:
* if we cannot remove remote resources remove what we can locally.
*/
if (!be_alloc)
dbuf_free(&front_info->dbuf_list, dbuf_cookie);
mutex_unlock(&evtchnl->u.req.req_io_lock);
return ret;
}
int xen_drm_front_fb_attach(struct xen_drm_front_info *front_info,
u64 dbuf_cookie, u64 fb_cookie, u32 width,
u32 height, u32 pixel_format)
{
struct xen_drm_front_evtchnl *evtchnl;
struct xen_drm_front_dbuf *buf;
struct xendispl_req *req;
unsigned long flags;
int ret;
evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
if (unlikely(!evtchnl))
return -EIO;
buf = dbuf_get(&front_info->dbuf_list, dbuf_cookie);
if (!buf)
return -EINVAL;
buf->fb_cookie = fb_cookie;
mutex_lock(&evtchnl->u.req.req_io_lock);
spin_lock_irqsave(&front_info->io_lock, flags);
req = be_prepare_req(evtchnl, XENDISPL_OP_FB_ATTACH);
req->op.fb_attach.dbuf_cookie = dbuf_cookie;
req->op.fb_attach.fb_cookie = fb_cookie;
req->op.fb_attach.width = width;
req->op.fb_attach.height = height;
req->op.fb_attach.pixel_format = pixel_format;
ret = be_stream_do_io(evtchnl, req);
spin_unlock_irqrestore(&front_info->io_lock, flags);
if (ret == 0)
ret = be_stream_wait_io(evtchnl);
mutex_unlock(&evtchnl->u.req.req_io_lock);
return ret;
}
int xen_drm_front_fb_detach(struct xen_drm_front_info *front_info,
u64 fb_cookie)
{
struct xen_drm_front_evtchnl *evtchnl;
struct xendispl_req *req;
unsigned long flags;
int ret;
evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
if (unlikely(!evtchnl))
return -EIO;
mutex_lock(&evtchnl->u.req.req_io_lock);
spin_lock_irqsave(&front_info->io_lock, flags);
req = be_prepare_req(evtchnl, XENDISPL_OP_FB_DETACH);
req->op.fb_detach.fb_cookie = fb_cookie;
ret = be_stream_do_io(evtchnl, req);
spin_unlock_irqrestore(&front_info->io_lock, flags);
if (ret == 0)
ret = be_stream_wait_io(evtchnl);
mutex_unlock(&evtchnl->u.req.req_io_lock);
return ret;
}
int xen_drm_front_page_flip(struct xen_drm_front_info *front_info,
int conn_idx, u64 fb_cookie)
{
struct xen_drm_front_evtchnl *evtchnl;
struct xendispl_req *req;
unsigned long flags;
int ret;
if (unlikely(conn_idx >= front_info->num_evt_pairs))
return -EINVAL;
evtchnl = &front_info->evt_pairs[conn_idx].req;
mutex_lock(&evtchnl->u.req.req_io_lock);
spin_lock_irqsave(&front_info->io_lock, flags);
req = be_prepare_req(evtchnl, XENDISPL_OP_PG_FLIP);
req->op.pg_flip.fb_cookie = fb_cookie;
ret = be_stream_do_io(evtchnl, req);
spin_unlock_irqrestore(&front_info->io_lock, flags);
if (ret == 0)
ret = be_stream_wait_io(evtchnl);
mutex_unlock(&evtchnl->u.req.req_io_lock);
return ret;
}
void xen_drm_front_on_frame_done(struct xen_drm_front_info *front_info,
int conn_idx, u64 fb_cookie)
{
struct xen_drm_front_drm_info *drm_info = front_info->drm_info;
if (unlikely(conn_idx >= front_info->cfg.num_connectors))
return;
xen_drm_front_kms_on_frame_done(&drm_info->pipeline[conn_idx],
fb_cookie);
}
void xen_drm_front_gem_object_free(struct drm_gem_object *obj)
{
struct xen_drm_front_drm_info *drm_info = obj->dev->dev_private;
int idx;
if (drm_dev_enter(obj->dev, &idx)) {
xen_drm_front_dbuf_destroy(drm_info->front_info,
xen_drm_front_dbuf_to_cookie(obj));
drm_dev_exit(idx);
} else {
dbuf_free(&drm_info->front_info->dbuf_list,
xen_drm_front_dbuf_to_cookie(obj));
}
xen_drm_front_gem_free_object_unlocked(obj);
}
static int xen_drm_drv_dumb_create(struct drm_file *filp,
struct drm_device *dev,
struct drm_mode_create_dumb *args)
{
struct xen_drm_front_drm_info *drm_info = dev->dev_private;
struct drm_gem_object *obj;
int ret;
/*
* Dumb creation is a two stage process: first we create a fully
* constructed GEM object which is communicated to the backend, and
* only after that we can create GEM's handle. This is done so,
* because of the possible races: once you create a handle it becomes
* immediately visible to user-space, so the latter can try accessing
* object without pages etc.
* For details also see drm_gem_handle_create
*/
args->pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
args->size = args->pitch * args->height;
obj = xen_drm_front_gem_create(dev, args->size);
if (IS_ERR(obj)) {
ret = PTR_ERR(obj);
goto fail;
}
ret = xen_drm_front_dbuf_create(drm_info->front_info,
xen_drm_front_dbuf_to_cookie(obj),
args->width, args->height, args->bpp,
args->size, 0,
xen_drm_front_gem_get_pages(obj));
if (ret)
goto fail_backend;
/* This is the tail of GEM object creation */
ret = drm_gem_handle_create(filp, obj, &args->handle);
if (ret)
goto fail_handle;
/* Drop reference from allocate - handle holds it now */
drm_gem_object_put(obj);
return 0;
fail_handle:
xen_drm_front_dbuf_destroy(drm_info->front_info,
xen_drm_front_dbuf_to_cookie(obj));
fail_backend:
/* drop reference from allocate */
drm_gem_object_put(obj);
fail:
DRM_ERROR("Failed to create dumb buffer: %d\n", ret);
return ret;
}
static void xen_drm_drv_release(struct drm_device *dev)
{
struct xen_drm_front_drm_info *drm_info = dev->dev_private;
struct xen_drm_front_info *front_info = drm_info->front_info;
xen_drm_front_kms_fini(drm_info);
drm_atomic_helper_shutdown(dev);
drm_mode_config_cleanup(dev);
if (front_info->cfg.be_alloc)
xenbus_switch_state(front_info->xb_dev,
XenbusStateInitialising);
kfree(drm_info);
}
DEFINE_DRM_GEM_FOPS(xen_drm_dev_fops);
static const struct drm_driver xen_drm_driver = {
.driver_features = DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC,
.release = xen_drm_drv_release,
.gem_prime_import_sg_table = xen_drm_front_gem_import_sg_table,
.dumb_create = xen_drm_drv_dumb_create,
.fops = &xen_drm_dev_fops,
.name = "xendrm-du",
.desc = "Xen PV DRM Display Unit",
.date = "20180221",
.major = 1,
.minor = 0,
};
static int xen_drm_drv_init(struct xen_drm_front_info *front_info)
{
struct device *dev = &front_info->xb_dev->dev;
struct xen_drm_front_drm_info *drm_info;
struct drm_device *drm_dev;
int ret;
if (drm_firmware_drivers_only())
return -ENODEV;
DRM_INFO("Creating %s\n", xen_drm_driver.desc);
drm_info = kzalloc(sizeof(*drm_info), GFP_KERNEL);
if (!drm_info) {
ret = -ENOMEM;
goto fail;
}
drm_info->front_info = front_info;
front_info->drm_info = drm_info;
drm_dev = drm_dev_alloc(&xen_drm_driver, dev);
if (IS_ERR(drm_dev)) {
ret = PTR_ERR(drm_dev);
goto fail_dev;
}
drm_info->drm_dev = drm_dev;
drm_dev->dev_private = drm_info;
ret = xen_drm_front_kms_init(drm_info);
if (ret) {
DRM_ERROR("Failed to initialize DRM/KMS, ret %d\n", ret);
goto fail_modeset;
}
ret = drm_dev_register(drm_dev, 0);
if (ret)
goto fail_register;
DRM_INFO("Initialized %s %d.%d.%d %s on minor %d\n",
xen_drm_driver.name, xen_drm_driver.major,
xen_drm_driver.minor, xen_drm_driver.patchlevel,
xen_drm_driver.date, drm_dev->primary->index);
return 0;
fail_register:
drm_dev_unregister(drm_dev);
fail_modeset:
drm_kms_helper_poll_fini(drm_dev);
drm_mode_config_cleanup(drm_dev);
drm_dev_put(drm_dev);
fail_dev:
kfree(drm_info);
front_info->drm_info = NULL;
fail:
return ret;
}
static void xen_drm_drv_fini(struct xen_drm_front_info *front_info)
{
struct xen_drm_front_drm_info *drm_info = front_info->drm_info;
struct drm_device *dev;
if (!drm_info)
return;
dev = drm_info->drm_dev;
if (!dev)
return;
/* Nothing to do if device is already unplugged */
if (drm_dev_is_unplugged(dev))
return;
drm_kms_helper_poll_fini(dev);
drm_dev_unplug(dev);
drm_dev_put(dev);
front_info->drm_info = NULL;
xen_drm_front_evtchnl_free_all(front_info);
dbuf_free_all(&front_info->dbuf_list);
/*
* If we are not using backend allocated buffers, then tell the
* backend we are ready to (re)initialize. Otherwise, wait for
* drm_driver.release.
*/
if (!front_info->cfg.be_alloc)
xenbus_switch_state(front_info->xb_dev,
XenbusStateInitialising);
}
static int displback_initwait(struct xen_drm_front_info *front_info)
{
struct xen_drm_front_cfg *cfg = &front_info->cfg;
int ret;
cfg->front_info = front_info;
ret = xen_drm_front_cfg_card(front_info, cfg);
if (ret < 0)
return ret;
DRM_INFO("Have %d connector(s)\n", cfg->num_connectors);
/* Create event channels for all connectors and publish */
ret = xen_drm_front_evtchnl_create_all(front_info);
if (ret < 0)
return ret;
return xen_drm_front_evtchnl_publish_all(front_info);
}
static int displback_connect(struct xen_drm_front_info *front_info)
{
xen_drm_front_evtchnl_set_state(front_info, EVTCHNL_STATE_CONNECTED);
return xen_drm_drv_init(front_info);
}
static void displback_disconnect(struct xen_drm_front_info *front_info)
{
if (!front_info->drm_info)
return;
/* Tell the backend to wait until we release the DRM driver. */
xenbus_switch_state(front_info->xb_dev, XenbusStateReconfiguring);
xen_drm_drv_fini(front_info);
}
static void displback_changed(struct xenbus_device *xb_dev,
enum xenbus_state backend_state)
{
struct xen_drm_front_info *front_info = dev_get_drvdata(&xb_dev->dev);
int ret;
DRM_DEBUG("Backend state is %s, front is %s\n",
xenbus_strstate(backend_state),
xenbus_strstate(xb_dev->state));
switch (backend_state) {
case XenbusStateReconfiguring:
case XenbusStateReconfigured:
case XenbusStateInitialised:
break;
case XenbusStateInitialising:
if (xb_dev->state == XenbusStateReconfiguring)
break;
/* recovering after backend unexpected closure */
displback_disconnect(front_info);
break;
case XenbusStateInitWait:
if (xb_dev->state == XenbusStateReconfiguring)
break;
/* recovering after backend unexpected closure */
displback_disconnect(front_info);
if (xb_dev->state != XenbusStateInitialising)
break;
ret = displback_initwait(front_info);
if (ret < 0)
xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
else
xenbus_switch_state(xb_dev, XenbusStateInitialised);
break;
case XenbusStateConnected:
if (xb_dev->state != XenbusStateInitialised)
break;
ret = displback_connect(front_info);
if (ret < 0) {
displback_disconnect(front_info);
xenbus_dev_fatal(xb_dev, ret, "connecting backend");
} else {
xenbus_switch_state(xb_dev, XenbusStateConnected);
}
break;
case XenbusStateClosing:
/*
* in this state backend starts freeing resources,
* so let it go into closed state, so we can also
* remove ours
*/
break;
case XenbusStateUnknown:
case XenbusStateClosed:
if (xb_dev->state == XenbusStateClosed)
break;
displback_disconnect(front_info);
break;
}
}
static int xen_drv_probe(struct xenbus_device *xb_dev,
const struct xenbus_device_id *id)
{
struct xen_drm_front_info *front_info;
struct device *dev = &xb_dev->dev;
int ret;
ret = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(64));
if (ret < 0) {
DRM_ERROR("Cannot setup DMA mask, ret %d", ret);
return ret;
}
front_info = devm_kzalloc(&xb_dev->dev,
sizeof(*front_info), GFP_KERNEL);
if (!front_info)
return -ENOMEM;
front_info->xb_dev = xb_dev;
spin_lock_init(&front_info->io_lock);
INIT_LIST_HEAD(&front_info->dbuf_list);
dev_set_drvdata(&xb_dev->dev, front_info);
return xenbus_switch_state(xb_dev, XenbusStateInitialising);
}
static void xen_drv_remove(struct xenbus_device *dev)
{
struct xen_drm_front_info *front_info = dev_get_drvdata(&dev->dev);
int to = 100;
xenbus_switch_state(dev, XenbusStateClosing);
/*
* On driver removal it is disconnected from XenBus,
* so no backend state change events come via .otherend_changed
* callback. This prevents us from exiting gracefully, e.g.
* signaling the backend to free event channels, waiting for its
* state to change to XenbusStateClosed and cleaning at our end.
* Normally when front driver removed backend will finally go into
* XenbusStateInitWait state.
*
* Workaround: read backend's state manually and wait with time-out.
*/
while ((xenbus_read_unsigned(front_info->xb_dev->otherend, "state",
XenbusStateUnknown) != XenbusStateInitWait) &&
--to)
msleep(10);
if (!to) {
unsigned int state;
state = xenbus_read_unsigned(front_info->xb_dev->otherend,
"state", XenbusStateUnknown);
DRM_ERROR("Backend state is %s while removing driver\n",
xenbus_strstate(state));
}
xen_drm_drv_fini(front_info);
xenbus_frontend_closed(dev);
}
static const struct xenbus_device_id xen_driver_ids[] = {
{ XENDISPL_DRIVER_NAME },
{ "" }
};
static struct xenbus_driver xen_driver = {
.ids = xen_driver_ids,
.probe = xen_drv_probe,
.remove = xen_drv_remove,
.otherend_changed = displback_changed,
.not_essential = true,
};
static int __init xen_drv_init(void)
{
/* At the moment we only support case with XEN_PAGE_SIZE == PAGE_SIZE */
if (XEN_PAGE_SIZE != PAGE_SIZE) {
DRM_ERROR(XENDISPL_DRIVER_NAME ": different kernel and Xen page sizes are not supported: XEN_PAGE_SIZE (%lu) != PAGE_SIZE (%lu)\n",
XEN_PAGE_SIZE, PAGE_SIZE);
return -ENODEV;
}
if (!xen_domain())
return -ENODEV;
if (!xen_has_pv_devices())
return -ENODEV;
DRM_INFO("Registering XEN PV " XENDISPL_DRIVER_NAME "\n");
return xenbus_register_frontend(&xen_driver);
}
static void __exit xen_drv_fini(void)
{
DRM_INFO("Unregistering XEN PV " XENDISPL_DRIVER_NAME "\n");
xenbus_unregister_driver(&xen_driver);
}
module_init(xen_drv_init);
module_exit(xen_drv_fini);
MODULE_DESCRIPTION("Xen para-virtualized display device frontend");
MODULE_LICENSE("GPL");
MODULE_ALIAS("xen:" XENDISPL_DRIVER_NAME);