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/* SPDX-License-Identifier: GPL-2.0 OR MIT */
* Xen para-virtual DRM device
* Copyright (C) 2016-2018 EPAM Systems Inc.
* Author: Oleksandr Andrushchenko <>
#ifndef __XEN_DRM_FRONT_H_
#define __XEN_DRM_FRONT_H_
#include <linux/scatterlist.h>
#include <drm/drm_connector.h>
#include <drm/drm_simple_kms_helper.h>
#include "xen_drm_front_cfg.h"
struct drm_device;
struct drm_framebuffer;
struct drm_gem_object;
struct drm_pending_vblank_event;
* DOC: Driver modes of operation in terms of display buffers used
* Depending on the requirements for the para-virtualized environment, namely
* requirements dictated by the accompanying DRM/(v)GPU drivers running in both
* host and guest environments, display buffers can be allocated by either
* frontend driver or backend.
* DOC: Buffers allocated by the frontend driver
* In this mode of operation driver allocates buffers from system memory.
* Note! If used with accompanying DRM/(v)GPU drivers this mode of operation
* may require IOMMU support on the platform, so accompanying DRM/vGPU
* hardware can still reach display buffer memory while importing PRIME
* buffers from the frontend driver.
* DOC: Buffers allocated by the backend
* This mode of operation is run-time configured via guest domain configuration
* through XenStore entries.
* For systems which do not provide IOMMU support, but having specific
* requirements for display buffers it is possible to allocate such buffers
* at backend side and share those with the frontend.
* For example, if host domain is 1:1 mapped and has DRM/GPU hardware expecting
* physically contiguous memory, this allows implementing zero-copying
* use-cases.
* Note, while using this scenario the following should be considered:
* #. If guest domain dies then pages/grants received from the backend
* cannot be claimed back
* #. Misbehaving guest may send too many requests to the
* backend exhausting its grant references and memory
* (consider this from security POV)
* DOC: Driver limitations
* #. Only primary plane without additional properties is supported.
* #. Only one video mode per connector supported which is configured
* via XenStore.
* #. All CRTCs operate at fixed frequency of 60Hz.
/* timeout in ms to wait for backend to respond */
* Note on usage of grant reference 0 as invalid grant reference:
* grant reference 0 is valid, but never exposed to a PV driver,
* because of the fact it is already in use/reserved by the PV console.
struct xen_drm_front_info {
struct xenbus_device *xb_dev;
struct xen_drm_front_drm_info *drm_info;
/* to protect data between backend IO code and interrupt handler */
spinlock_t io_lock;
int num_evt_pairs;
struct xen_drm_front_evtchnl_pair *evt_pairs;
struct xen_drm_front_cfg cfg;
/* display buffers */
struct list_head dbuf_list;
struct xen_drm_front_drm_pipeline {
struct xen_drm_front_drm_info *drm_info;
int index;
struct drm_simple_display_pipe pipe;
struct drm_connector conn;
/* These are only for connector mode checking */
int width, height;
struct drm_pending_vblank_event *pending_event;
struct delayed_work pflip_to_worker;
bool conn_connected;
struct xen_drm_front_drm_info {
struct xen_drm_front_info *front_info;
struct drm_device *drm_dev;
struct xen_drm_front_drm_pipeline pipeline[XEN_DRM_FRONT_MAX_CRTCS];
static inline u64 xen_drm_front_fb_to_cookie(struct drm_framebuffer *fb)
return (uintptr_t)fb;
static inline u64 xen_drm_front_dbuf_to_cookie(struct drm_gem_object *gem_obj)
return (uintptr_t)gem_obj;
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);
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);
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);
int xen_drm_front_fb_detach(struct xen_drm_front_info *front_info,
u64 fb_cookie);
int xen_drm_front_page_flip(struct xen_drm_front_info *front_info,
int conn_idx, u64 fb_cookie);
void xen_drm_front_on_frame_done(struct xen_drm_front_info *front_info,
int conn_idx, u64 fb_cookie);
void xen_drm_front_gem_object_free(struct drm_gem_object *obj);
#endif /* __XEN_DRM_FRONT_H_ */