Re: [PATCH 1/9] drm/xen-front: Introduce Xen para-virtualized frontend driver

From: Oleksandr Andrushchenko
Date: Wed Feb 21 2018 - 04:11:16 EST

On 02/21/2018 11:09 AM, Juergen Gross wrote:
On 21/02/18 09:47, Oleksandr Andrushchenko wrote:
On 02/21/2018 10:19 AM, Juergen Gross wrote:
On 21/02/18 09:03, Oleksandr Andrushchenko wrote:
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

Introduce skeleton of the para-virtualized Xen display
frontend driver. This patch only adds required
essential stubs.

Signed-off-by: Oleksandr Andrushchenko
<oleksandr_andrushchenko@xxxxxxxx>
---
 drivers/gpu/drm/Kconfig | 2 +
 drivers/gpu/drm/Makefile | 1 +
 drivers/gpu/drm/xen/Kconfig | 17 ++++++++
 drivers/gpu/drm/xen/Makefile | 5 +++
 drivers/gpu/drm/xen/xen_drm_front.c | 83
+++++++++++++++++++++++++++++++++++++
 5 files changed, 108 insertions(+)
 create mode 100644 drivers/gpu/drm/xen/Kconfig
 create mode 100644 drivers/gpu/drm/xen/Makefile
 create mode 100644 drivers/gpu/drm/xen/xen_drm_front.c

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index deeefa7a1773..757825ac60df 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -289,6 +289,8 @@ source "drivers/gpu/drm/pl111/Kconfig"
  source "drivers/gpu/drm/tve200/Kconfig"
 +source "drivers/gpu/drm/xen/Kconfig"
+
 # Keep legacy drivers last
  menuconfig DRM_LEGACY
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 50093ff4479b..9d66657ea117 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -103,3 +103,4 @@ obj-$(CONFIG_DRM_MXSFB)ÂÂÂ += mxsfb/
 obj-$(CONFIG_DRM_TINYDRM) += tinydrm/
 obj-$(CONFIG_DRM_PL111) += pl111/
 obj-$(CONFIG_DRM_TVE200) += tve200/
+obj-$(CONFIG_DRM_XEN) += xen/
diff --git a/drivers/gpu/drm/xen/Kconfig b/drivers/gpu/drm/xen/Kconfig
new file mode 100644
index 000000000000..4cca160782ab
--- /dev/null
+++ b/drivers/gpu/drm/xen/Kconfig
@@ -0,0 +1,17 @@
+config DRM_XEN
+ÂÂÂ bool "DRM Support for Xen guest OS"
+ÂÂÂ depends on XEN
+ÂÂÂ help
+ÂÂÂÂÂ Choose this option if you want to enable DRM support
+ÂÂÂÂÂ for Xen.
+
+config DRM_XEN_FRONTEND
+ÂÂÂ tristate "Para-virtualized frontend driver for Xen guest OS"
+ÂÂÂ depends on DRM_XEN
+ÂÂÂ depends on DRM
+ÂÂÂ select DRM_KMS_HELPER
+ÂÂÂ select VIDEOMODE_HELPERS
+ÂÂÂ select XEN_XENBUS_FRONTEND
+ÂÂÂ help
+ÂÂÂÂÂ Choose this option if you want to enable a para-virtualized
+ÂÂÂÂÂ frontend DRM/KMS driver for Xen guest OSes.
diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
new file mode 100644
index 000000000000..967074d348f6
--- /dev/null
+++ b/drivers/gpu/drm/xen/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+drm_xen_front-objs := xen_drm_front.o
+
+obj-$(CONFIG_DRM_XEN_FRONTEND) += drm_xen_front.o
diff --git a/drivers/gpu/drm/xen/xen_drm_front.c
b/drivers/gpu/drm/xen/xen_drm_front.c
new file mode 100644
index 000000000000..fd372fb464a1
--- /dev/null
+++ b/drivers/gpu/drm/xen/xen_drm_front.c
@@ -0,0 +1,83 @@
+/*
+ *Â Xen para-virtual DRM device
+ *
+ *ÂÂ This program is free software; you can redistribute it and/or
modify
+ *ÂÂ it under the terms of the GNU General Public License as
published by
+ *ÂÂ the Free Software Foundation; either version 2 of the License, or
+ *ÂÂ (at your option) any later version.
+ *
+ *ÂÂ This program is distributed in the hope that it will be useful,
+ *ÂÂ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *ÂÂ GNU General Public License for more details.
Use SPDX identifier instead (same applies for all other new
sources):

// SPDX-License-Identifier: GPL-2.0
Will update, thank you
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
+ */
+
+#include <drm/drmP.h>
+
+#include <xen/platform_pci.h>
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+
+#include <xen/interface/io/displif.h>
+
+static void backend_on_changed(struct xenbus_device *xb_dev,
+ÂÂÂÂÂÂÂ enum xenbus_state backend_state)
+{
+}
+
+static int xen_drv_probe(struct xenbus_device *xb_dev,
+ÂÂÂÂÂÂÂ const struct xenbus_device_id *id)
+{
+ÂÂÂ return 0;
+}
+
+static int xen_drv_remove(struct xenbus_device *dev)
+{
+ÂÂÂ return 0;
+}
+
+static const struct xenbus_device_id xen_drv_ids[] = {
+ÂÂÂ { XENDISPL_DRIVER_NAME },
+ÂÂÂ { "" }
+};
+
+static struct xenbus_driver xen_driver = {
+ÂÂÂ .ids = xen_drv_ids,
+ÂÂÂ .probe = xen_drv_probe,
+ÂÂÂ .remove = xen_drv_remove,
+ÂÂÂ .otherend_changed = backend_on_changed,
+};
+
+static int __init xen_drv_init(void)
+{
+ÂÂÂ if (!xen_domain())
+ÂÂÂÂÂÂÂ return -ENODEV;
+
+ÂÂÂ if (xen_initial_domain()) {
+ÂÂÂÂÂÂÂ DRM_ERROR(XENDISPL_DRIVER_NAME " cannot run in initial
domain\n");
+ÂÂÂÂÂÂÂ return -ENODEV;
+ÂÂÂ }
Why not? Wouldn't that be possible in case of the backend living in a
driver domain?
It is possible (and in my use-case backend indeed runs in
a driver domain). I was just not sure if it is really a
good idea to allow that. If you think this is ok, then
I'll remove this check
I don't think the driver should decide that. This would be the job of
Xen tools IMO.
Agree, will remove

Juergen