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

[Oleksandr Andrushchenko]

On 02/23/2018 04:39 PM, Boris Ostrovsky wrote:

On 02/23/2018 01:37 AM, Oleksandr Andrushchenko wrote:

On 02/23/2018 12:23 AM, Boris Ostrovsky wrote:

On 02/21/2018 03:03 AM, Oleksandr Andrushchenko wrote:

+static struct xenbus_driver xen_driver = {
+.ids = xen_drv_ids,
+.probe = xen_drv_probe,
+.remove = xen_drv_remove,
+.otherend_changed = backend_on_changed,

What does "_on_" stand for?

Well, it is somewhat like a hint that this is called "on" event,
e.g. event when the other end state has changed, backend in this
case. It could be something like "backend_on_state_changed"

If you look at other xenbus_drivers none of the uses this so I think we
should stick to conventional naming. (and the same applies to other
backend_on_* routines).

ok, no problem. will rename to be aligned with other frontends


-boris

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

[Oleksandr Andrushchenko]

On 02/23/2018 04:39 PM, Boris Ostrovsky wrote:

On 02/23/2018 01:37 AM, Oleksandr Andrushchenko wrote:

On 02/23/2018 12:23 AM, Boris Ostrovsky wrote:

On 02/21/2018 03:03 AM, Oleksandr Andrushchenko wrote:

+static struct xenbus_driver xen_driver = {
+.ids = xen_drv_ids,
+.probe = xen_drv_probe,
+.remove = xen_drv_remove,
+.otherend_changed = backend_on_changed,

What does "_on_" stand for?

Well, it is somewhat like a hint that this is called "on" event,
e.g. event when the other end state has changed, backend in this
case. It could be something like "backend_on_state_changed"

If you look at other xenbus_drivers none of the uses this so I think we
should stick to conventional naming. (and the same applies to other
backend_on_* routines).

ok, no problem. will rename to be aligned with other frontends


-boris

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

[Boris Ostrovsky]

On 02/23/2018 01:37 AM, Oleksandr Andrushchenko wrote:
> On 02/23/2018 12:23 AM, Boris Ostrovsky wrote:
>> On 02/21/2018 03:03 AM, Oleksandr Andrushchenko wrote:
>>> +static struct xenbus_driver xen_driver = {
>>> +.ids = xen_drv_ids,
>>> +.probe = xen_drv_probe,
>>> +.remove = xen_drv_remove,
>>> +.otherend_changed = backend_on_changed,
>> What does "_on_" stand for?
> Well, it is somewhat like a hint that this is called "on" event,
> e.g. event when the other end state has changed, backend in this
> case. It could be something like "backend_on_state_changed"

If you look at other xenbus_drivers none of the uses this so I think we
should stick to conventional naming. (and the same applies to other
backend_on_* routines).

-boris

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

[Boris Ostrovsky]

On 02/23/2018 01:37 AM, Oleksandr Andrushchenko wrote:
> On 02/23/2018 12:23 AM, Boris Ostrovsky wrote:
>> On 02/21/2018 03:03 AM, Oleksandr Andrushchenko wrote:
>>> +static struct xenbus_driver xen_driver = {
>>> +.ids = xen_drv_ids,
>>> +.probe = xen_drv_probe,
>>> +.remove = xen_drv_remove,
>>> +.otherend_changed = backend_on_changed,
>> What does "_on_" stand for?
> Well, it is somewhat like a hint that this is called "on" event,
> e.g. event when the other end state has changed, backend in this
> case. It could be something like "backend_on_state_changed"

If you look at other xenbus_drivers none of the uses this so I think we
should stick to conventional naming. (and the same applies to other
backend_on_* routines).

-boris

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

[Oleksandr Andrushchenko]

On 02/23/2018 12:23 AM, Boris Ostrovsky wrote:

On 02/21/2018 03:03 AM, Oleksandr Andrushchenko wrote:

+static struct xenbus_driver xen_driver = {
+   .ids = xen_drv_ids,
+   .probe = xen_drv_probe,
+   .remove = xen_drv_remove,
+   .otherend_changed = backend_on_changed,

What does "_on_" stand for?

Well, it is somewhat like a hint that this is called "on" event,
e.g. event when the other end state has changed, backend in this
case. It could be something like "backend_on_state_changed"

-boris

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

[Oleksandr Andrushchenko]

On 02/23/2018 12:23 AM, Boris Ostrovsky wrote:

On 02/21/2018 03:03 AM, Oleksandr Andrushchenko wrote:

+static struct xenbus_driver xen_driver = {
+   .ids = xen_drv_ids,
+   .probe = xen_drv_probe,
+   .remove = xen_drv_remove,
+   .otherend_changed = backend_on_changed,

What does "_on_" stand for?

Well, it is somewhat like a hint that this is called "on" event,
e.g. event when the other end state has changed, backend in this
case. It could be something like "backend_on_state_changed"

-boris

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

[Boris Ostrovsky]

On 02/21/2018 03:03 AM, Oleksandr Andrushchenko wrote:
> +static struct xenbus_driver xen_driver = {
> + .ids = xen_drv_ids,
> + .probe = xen_drv_probe,
> + .remove = xen_drv_remove,
> + .otherend_changed = backend_on_changed,

What does "_on_" stand for?

-boris

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

[Boris Ostrovsky]

On 02/21/2018 03:03 AM, Oleksandr Andrushchenko wrote:
> +static struct xenbus_driver xen_driver = {
> + .ids = xen_drv_ids,
> + .probe = xen_drv_probe,
> + .remove = xen_drv_remove,
> + .otherend_changed = backend_on_changed,

What does "_on_" stand for?

-boris

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

[Oleksandr Andrushchenko]

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 

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

Signed-off-by: Oleksandr Andrushchenko

---
   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-$(CONFIG_DRM_MXSFB)    += mxsfb/
   obj-$(CONFIG_DRM_TINYDRM) += tinydrm/
   obj-$(CONFIG_DRM_PL111) += pl111/
   obj-$(CONFIG_DRM_TVE200) += tve200/
+obj-$(CONFIG_DRM_XEN) += xen/
diff --git a/drivers/gpu/drm/xen/Kconfig b/drivers/gpu/drm/xen/Kconfig
new file mode 100644
index ..4cca160782ab
--- /dev/null
+++ b/drivers/gpu/drm/xen/Kconfig
@@ -0,0 +1,17 @@
+config DRM_XEN
+    bool "DRM Support for Xen guest OS"
+    depends on XEN
+    help
+  Choose this option if you want to enable DRM support
+  for Xen.
+
+config DRM_XEN_FRONTEND
+    tristate "Para-virtualized frontend driver for Xen guest OS"
+    depends on DRM_XEN
+    depends on DRM
+    select DRM_KMS_HELPER
+    select VIDEOMODE_HELPERS
+    select XEN_XENBUS_FRONTEND
+    help
+  Choose this option if you want to enable a para-virtualized
+  frontend DRM/KMS driver for Xen guest OSes.
diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
new file mode 100644
index ..967074d348f6
--- /dev/null
+++ b/drivers/gpu/drm/xen/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+drm_xen_front-objs := xen_drm_front.o
+
+obj-$(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 ..fd372fb464a1
--- /dev/null
+++ b/drivers/gpu/drm/xen/xen_drm_front.c
@@ -0,0 +1,83 @@
+/*
+ *  Xen para-virtual DRM device
+ *
+ *   This program is free software; you can redistribute it and/or
modify
+ *   it under the terms of the GNU General Public License as
published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   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 
+ */
+
+#include 
+
+#include 
+#include 
+#include 
+
+#include 
+
+static void backend_on_changed(struct xenbus_device *xb_dev,
+    enum xenbus_state backend_state)
+{
+}
+
+static int xen_drv_probe(struct xenbus_device *xb_dev,
+    const struct xenbus_device_id *id)
+{
+    return 0;
+}
+
+static int xen_drv_remove(struct xenbus_device *dev)
+{
+    return 0;
+}
+
+static const struct xenbus_device_id xen_drv_ids[] = {
+    { XENDISPL_DRIVER_NAME },
+    { "" }
+};
+
+static struct xenbus_driver xen_driver = {
+    .ids = xen_drv_ids,
+    .probe = xen_drv_probe,
+    .remove = xen_drv_remove,
+    .otherend_changed = backend_on_changed,
+};
+
+static int __init xen_drv_init(void)
+{
+    if (!xen_domain())
+    return -ENODEV;
+
+    if (xen_initial_domain()) {
+    DRM_ERROR(XENDISPL_DRIVER_NAME " cannot run in initial
domain\n");
+    return -ENODEV;
+    }

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 

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

[Oleksandr Andrushchenko]

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 

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

Signed-off-by: Oleksandr Andrushchenko

---
   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-$(CONFIG_DRM_MXSFB)    += mxsfb/
   obj-$(CONFIG_DRM_TINYDRM) += tinydrm/
   obj-$(CONFIG_DRM_PL111) += pl111/
   obj-$(CONFIG_DRM_TVE200) += tve200/
+obj-$(CONFIG_DRM_XEN) += xen/
diff --git a/drivers/gpu/drm/xen/Kconfig b/drivers/gpu/drm/xen/Kconfig
new file mode 100644
index ..4cca160782ab
--- /dev/null
+++ b/drivers/gpu/drm/xen/Kconfig
@@ -0,0 +1,17 @@
+config DRM_XEN
+    bool "DRM Support for Xen guest OS"
+    depends on XEN
+    help
+  Choose this option if you want to enable DRM support
+  for Xen.
+
+config DRM_XEN_FRONTEND
+    tristate "Para-virtualized frontend driver for Xen guest OS"
+    depends on DRM_XEN
+    depends on DRM
+    select DRM_KMS_HELPER
+    select VIDEOMODE_HELPERS
+    select XEN_XENBUS_FRONTEND
+    help
+  Choose this option if you want to enable a para-virtualized
+  frontend DRM/KMS driver for Xen guest OSes.
diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
new file mode 100644
index ..967074d348f6
--- /dev/null
+++ b/drivers/gpu/drm/xen/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+drm_xen_front-objs := xen_drm_front.o
+
+obj-$(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 ..fd372fb464a1
--- /dev/null
+++ b/drivers/gpu/drm/xen/xen_drm_front.c
@@ -0,0 +1,83 @@
+/*
+ *  Xen para-virtual DRM device
+ *
+ *   This program is free software; you can redistribute it and/or
modify
+ *   it under the terms of the GNU General Public License as
published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   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 
+ */
+
+#include 
+
+#include 
+#include 
+#include 
+
+#include 
+
+static void backend_on_changed(struct xenbus_device *xb_dev,
+    enum xenbus_state backend_state)
+{
+}
+
+static int xen_drv_probe(struct xenbus_device *xb_dev,
+    const struct xenbus_device_id *id)
+{
+    return 0;
+}
+
+static int xen_drv_remove(struct xenbus_device *dev)
+{
+    return 0;
+}
+
+static const struct xenbus_device_id xen_drv_ids[] = {
+    { XENDISPL_DRIVER_NAME },
+    { "" }
+};
+
+static struct xenbus_driver xen_driver = {
+    .ids = xen_drv_ids,
+    .probe = xen_drv_probe,
+    .remove = xen_drv_remove,
+    .otherend_changed = backend_on_changed,
+};
+
+static int __init xen_drv_init(void)
+{
+    if (!xen_domain())
+    return -ENODEV;
+
+    if (xen_initial_domain()) {
+    DRM_ERROR(XENDISPL_DRIVER_NAME " cannot run in initial
domain\n");
+    return -ENODEV;
+    }

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

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

[Juergen Gross]

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 
>>>
>>> Introduce skeleton of the para-virtualized Xen display
>>> frontend driver. This patch only adds required
>>> essential stubs.
>>>
>>> Signed-off-by: Oleksandr Andrushchenko
>>> 
>>> ---
>>>   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-$(CONFIG_DRM_MXSFB)    += mxsfb/
>>>   obj-$(CONFIG_DRM_TINYDRM) += tinydrm/
>>>   obj-$(CONFIG_DRM_PL111) += pl111/
>>>   obj-$(CONFIG_DRM_TVE200) += tve200/
>>> +obj-$(CONFIG_DRM_XEN) += xen/
>>> diff --git a/drivers/gpu/drm/xen/Kconfig b/drivers/gpu/drm/xen/Kconfig
>>> new file mode 100644
>>> index ..4cca160782ab
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/xen/Kconfig
>>> @@ -0,0 +1,17 @@
>>> +config DRM_XEN
>>> +    bool "DRM Support for Xen guest OS"
>>> +    depends on XEN
>>> +    help
>>> +  Choose this option if you want to enable DRM support
>>> +  for Xen.
>>> +
>>> +config DRM_XEN_FRONTEND
>>> +    tristate "Para-virtualized frontend driver for Xen guest OS"
>>> +    depends on DRM_XEN
>>> +    depends on DRM
>>> +    select DRM_KMS_HELPER
>>> +    select VIDEOMODE_HELPERS
>>> +    select XEN_XENBUS_FRONTEND
>>> +    help
>>> +  Choose this option if you want to enable a para-virtualized
>>> +  frontend DRM/KMS driver for Xen guest OSes.
>>> diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
>>> new file mode 100644
>>> index ..967074d348f6
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/xen/Makefile
>>> @@ -0,0 +1,5 @@
>>> +# SPDX-License-Identifier: GPL-2.0
>>> +
>>> +drm_xen_front-objs := xen_drm_front.o
>>> +
>>> +obj-$(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 ..fd372fb464a1
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/xen/xen_drm_front.c
>>> @@ -0,0 +1,83 @@
>>> +/*
>>> + *  Xen para-virtual DRM device
>>> + *
>>> + *   This program is free software; you can redistribute it and/or
>>> modify
>>> + *   it under the terms of the GNU General Public License as
>>> published by
>>> + *   the Free Software Foundation; either version 2 of the License, or
>>> + *   (at your option) any later version.
>>> + *
>>> + *   This program is distributed in the hope that it will be useful,
>>> + *   but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>> + *   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 
>>> + */
>>> +
>>> +#include 
>>> +
>>> +#include 
>>> +#include 
>>> +#include 
>>> +
>>> +#include 
>>> +
>>> +static void backend_on_changed(struct xenbus_device *xb_dev,
>>> +    enum xenbus_state backend_state)
>>> +{
>>> +}
>>> +
>>> +static int xen_drv_probe(struct xenbus_device *xb_dev,
>>> +    const struct xenbus_device_id *id)
>>> +{
>>> +    return 0;
>>> +}
>>> +
>>> +static int xen_drv_remove(struct xenbus_device *dev)
>>> +{
>>> +    return 0;
>>> +}
>>> +
>>> +static const struct xenbus_device_id xen_drv_ids[] = {
>>> +    { XENDISPL_DRIVER_NAME },
>>> +    { "" }
>>> +};
>>> +
>>> +static struct xenbus_driver xen_driver = {
>>> +    .ids = xen_drv_ids,
>>> +    .probe = xen_drv_probe,
>>> +    .remove = xen_drv_remove,
>>> +    .otherend_changed = backend_on_changed,
>>> +};
>>> +
>>> +static int __init xen_drv_init(void)
>>> +{
>>> +    if (!xen_domain())
>>> +    return 

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

[Juergen Gross]

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 
>>>
>>> Introduce skeleton of the para-virtualized Xen display
>>> frontend driver. This patch only adds required
>>> essential stubs.
>>>
>>> Signed-off-by: Oleksandr Andrushchenko
>>> 
>>> ---
>>>   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-$(CONFIG_DRM_MXSFB)    += mxsfb/
>>>   obj-$(CONFIG_DRM_TINYDRM) += tinydrm/
>>>   obj-$(CONFIG_DRM_PL111) += pl111/
>>>   obj-$(CONFIG_DRM_TVE200) += tve200/
>>> +obj-$(CONFIG_DRM_XEN) += xen/
>>> diff --git a/drivers/gpu/drm/xen/Kconfig b/drivers/gpu/drm/xen/Kconfig
>>> new file mode 100644
>>> index ..4cca160782ab
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/xen/Kconfig
>>> @@ -0,0 +1,17 @@
>>> +config DRM_XEN
>>> +    bool "DRM Support for Xen guest OS"
>>> +    depends on XEN
>>> +    help
>>> +  Choose this option if you want to enable DRM support
>>> +  for Xen.
>>> +
>>> +config DRM_XEN_FRONTEND
>>> +    tristate "Para-virtualized frontend driver for Xen guest OS"
>>> +    depends on DRM_XEN
>>> +    depends on DRM
>>> +    select DRM_KMS_HELPER
>>> +    select VIDEOMODE_HELPERS
>>> +    select XEN_XENBUS_FRONTEND
>>> +    help
>>> +  Choose this option if you want to enable a para-virtualized
>>> +  frontend DRM/KMS driver for Xen guest OSes.
>>> diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
>>> new file mode 100644
>>> index ..967074d348f6
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/xen/Makefile
>>> @@ -0,0 +1,5 @@
>>> +# SPDX-License-Identifier: GPL-2.0
>>> +
>>> +drm_xen_front-objs := xen_drm_front.o
>>> +
>>> +obj-$(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 ..fd372fb464a1
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/xen/xen_drm_front.c
>>> @@ -0,0 +1,83 @@
>>> +/*
>>> + *  Xen para-virtual DRM device
>>> + *
>>> + *   This program is free software; you can redistribute it and/or
>>> modify
>>> + *   it under the terms of the GNU General Public License as
>>> published by
>>> + *   the Free Software Foundation; either version 2 of the License, or
>>> + *   (at your option) any later version.
>>> + *
>>> + *   This program is distributed in the hope that it will be useful,
>>> + *   but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>> + *   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 
>>> + */
>>> +
>>> +#include 
>>> +
>>> +#include 
>>> +#include 
>>> +#include 
>>> +
>>> +#include 
>>> +
>>> +static void backend_on_changed(struct xenbus_device *xb_dev,
>>> +    enum xenbus_state backend_state)
>>> +{
>>> +}
>>> +
>>> +static int xen_drv_probe(struct xenbus_device *xb_dev,
>>> +    const struct xenbus_device_id *id)
>>> +{
>>> +    return 0;
>>> +}
>>> +
>>> +static int xen_drv_remove(struct xenbus_device *dev)
>>> +{
>>> +    return 0;
>>> +}
>>> +
>>> +static const struct xenbus_device_id xen_drv_ids[] = {
>>> +    { XENDISPL_DRIVER_NAME },
>>> +    { "" }
>>> +};
>>> +
>>> +static struct xenbus_driver xen_driver = {
>>> +    .ids = xen_drv_ids,
>>> +    .probe = xen_drv_probe,
>>> +    .remove = xen_drv_remove,
>>> +    .otherend_changed = backend_on_changed,
>>> +};
>>> +
>>> +static int __init xen_drv_init(void)
>>> +{
>>> +    if (!xen_domain())
>>> +    return -ENODEV;
>>> +
>>> +    if (xen_initial_domain()) {
>>> +    DRM_ERROR(XENDISPL_DRIVER_NAME " cannot run 

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

[Oleksandr Andrushchenko]

On 02/21/2018 10:19 AM, Juergen Gross wrote:

On 21/02/18 09:03, Oleksandr Andrushchenko wrote:

From: Oleksandr Andrushchenko 

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

Signed-off-by: Oleksandr Andrushchenko 
---
  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-$(CONFIG_DRM_MXSFB) += mxsfb/
  obj-$(CONFIG_DRM_TINYDRM) += tinydrm/
  obj-$(CONFIG_DRM_PL111) += pl111/
  obj-$(CONFIG_DRM_TVE200) += tve200/
+obj-$(CONFIG_DRM_XEN) += xen/
diff --git a/drivers/gpu/drm/xen/Kconfig b/drivers/gpu/drm/xen/Kconfig
new file mode 100644
index ..4cca160782ab
--- /dev/null
+++ b/drivers/gpu/drm/xen/Kconfig
@@ -0,0 +1,17 @@
+config DRM_XEN
+   bool "DRM Support for Xen guest OS"
+   depends on XEN
+   help
+ Choose this option if you want to enable DRM support
+ for Xen.
+
+config DRM_XEN_FRONTEND
+   tristate "Para-virtualized frontend driver for Xen guest OS"
+   depends on DRM_XEN
+   depends on DRM
+   select DRM_KMS_HELPER
+   select VIDEOMODE_HELPERS
+   select XEN_XENBUS_FRONTEND
+   help
+ Choose this option if you want to enable a para-virtualized
+ frontend DRM/KMS driver for Xen guest OSes.
diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
new file mode 100644
index ..967074d348f6
--- /dev/null
+++ b/drivers/gpu/drm/xen/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+drm_xen_front-objs := xen_drm_front.o
+
+obj-$(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 ..fd372fb464a1
--- /dev/null
+++ b/drivers/gpu/drm/xen/xen_drm_front.c
@@ -0,0 +1,83 @@
+/*
+ *  Xen para-virtual DRM device
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   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 
+ */
+
+#include 
+
+#include 
+#include 
+#include 
+
+#include 
+
+static void backend_on_changed(struct xenbus_device *xb_dev,
+   enum xenbus_state backend_state)
+{
+}
+
+static int xen_drv_probe(struct xenbus_device *xb_dev,
+   const struct xenbus_device_id *id)
+{
+   return 0;
+}
+
+static int xen_drv_remove(struct xenbus_device *dev)
+{
+   return 0;
+}
+
+static const struct xenbus_device_id xen_drv_ids[] = {
+   { XENDISPL_DRIVER_NAME },
+   { "" }
+};
+
+static struct xenbus_driver xen_driver = {
+   .ids = xen_drv_ids,
+   .probe = xen_drv_probe,
+   .remove = xen_drv_remove,
+   .otherend_changed = backend_on_changed,
+};
+
+static int __init xen_drv_init(void)
+{
+   if (!xen_domain())
+   return -ENODEV;
+
+   if (xen_initial_domain()) {
+   DRM_ERROR(XENDISPL_DRIVER_NAME " cannot run in initial 
domain\n");
+   return -ENODEV;
+   }

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


Juergen

Thank you,
Oleksandr

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

[Oleksandr Andrushchenko]

On 02/21/2018 10:19 AM, Juergen Gross wrote:

On 21/02/18 09:03, Oleksandr Andrushchenko wrote:

From: Oleksandr Andrushchenko 

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

Signed-off-by: Oleksandr Andrushchenko 
---
  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-$(CONFIG_DRM_MXSFB) += mxsfb/
  obj-$(CONFIG_DRM_TINYDRM) += tinydrm/
  obj-$(CONFIG_DRM_PL111) += pl111/
  obj-$(CONFIG_DRM_TVE200) += tve200/
+obj-$(CONFIG_DRM_XEN) += xen/
diff --git a/drivers/gpu/drm/xen/Kconfig b/drivers/gpu/drm/xen/Kconfig
new file mode 100644
index ..4cca160782ab
--- /dev/null
+++ b/drivers/gpu/drm/xen/Kconfig
@@ -0,0 +1,17 @@
+config DRM_XEN
+   bool "DRM Support for Xen guest OS"
+   depends on XEN
+   help
+ Choose this option if you want to enable DRM support
+ for Xen.
+
+config DRM_XEN_FRONTEND
+   tristate "Para-virtualized frontend driver for Xen guest OS"
+   depends on DRM_XEN
+   depends on DRM
+   select DRM_KMS_HELPER
+   select VIDEOMODE_HELPERS
+   select XEN_XENBUS_FRONTEND
+   help
+ Choose this option if you want to enable a para-virtualized
+ frontend DRM/KMS driver for Xen guest OSes.
diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
new file mode 100644
index ..967074d348f6
--- /dev/null
+++ b/drivers/gpu/drm/xen/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+drm_xen_front-objs := xen_drm_front.o
+
+obj-$(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 ..fd372fb464a1
--- /dev/null
+++ b/drivers/gpu/drm/xen/xen_drm_front.c
@@ -0,0 +1,83 @@
+/*
+ *  Xen para-virtual DRM device
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   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 
+ */
+
+#include 
+
+#include 
+#include 
+#include 
+
+#include 
+
+static void backend_on_changed(struct xenbus_device *xb_dev,
+   enum xenbus_state backend_state)
+{
+}
+
+static int xen_drv_probe(struct xenbus_device *xb_dev,
+   const struct xenbus_device_id *id)
+{
+   return 0;
+}
+
+static int xen_drv_remove(struct xenbus_device *dev)
+{
+   return 0;
+}
+
+static const struct xenbus_device_id xen_drv_ids[] = {
+   { XENDISPL_DRIVER_NAME },
+   { "" }
+};
+
+static struct xenbus_driver xen_driver = {
+   .ids = xen_drv_ids,
+   .probe = xen_drv_probe,
+   .remove = xen_drv_remove,
+   .otherend_changed = backend_on_changed,
+};
+
+static int __init xen_drv_init(void)
+{
+   if (!xen_domain())
+   return -ENODEV;
+
+   if (xen_initial_domain()) {
+   DRM_ERROR(XENDISPL_DRIVER_NAME " cannot run in initial 
domain\n");
+   return -ENODEV;
+   }

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


Juergen

Thank you,
Oleksandr

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

[Juergen Gross]

On 21/02/18 09:03, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko 
> 
> Introduce skeleton of the para-virtualized Xen display
> frontend driver. This patch only adds required
> essential stubs.
> 
> Signed-off-by: Oleksandr Andrushchenko 
> ---
>  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-$(CONFIG_DRM_MXSFB)   += mxsfb/
>  obj-$(CONFIG_DRM_TINYDRM) += tinydrm/
>  obj-$(CONFIG_DRM_PL111) += pl111/
>  obj-$(CONFIG_DRM_TVE200) += tve200/
> +obj-$(CONFIG_DRM_XEN) += xen/
> diff --git a/drivers/gpu/drm/xen/Kconfig b/drivers/gpu/drm/xen/Kconfig
> new file mode 100644
> index ..4cca160782ab
> --- /dev/null
> +++ b/drivers/gpu/drm/xen/Kconfig
> @@ -0,0 +1,17 @@
> +config DRM_XEN
> + bool "DRM Support for Xen guest OS"
> + depends on XEN
> + help
> +   Choose this option if you want to enable DRM support
> +   for Xen.
> +
> +config DRM_XEN_FRONTEND
> + tristate "Para-virtualized frontend driver for Xen guest OS"
> + depends on DRM_XEN
> + depends on DRM
> + select DRM_KMS_HELPER
> + select VIDEOMODE_HELPERS
> + select XEN_XENBUS_FRONTEND
> + help
> +   Choose this option if you want to enable a para-virtualized
> +   frontend DRM/KMS driver for Xen guest OSes.
> diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
> new file mode 100644
> index ..967074d348f6
> --- /dev/null
> +++ b/drivers/gpu/drm/xen/Makefile
> @@ -0,0 +1,5 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +drm_xen_front-objs := xen_drm_front.o
> +
> +obj-$(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 ..fd372fb464a1
> --- /dev/null
> +++ b/drivers/gpu/drm/xen/xen_drm_front.c
> @@ -0,0 +1,83 @@
> +/*
> + *  Xen para-virtual DRM device
> + *
> + *   This program is free software; you can redistribute it and/or modify
> + *   it under the terms of the GNU General Public License as published by
> + *   the Free Software Foundation; either version 2 of the License, or
> + *   (at your option) any later version.
> + *
> + *   This program is distributed in the hope that it will be useful,
> + *   but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *   GNU General Public License for more details.

Use SPDX identifier instead (same applies for all other new
sources):

// SPDX-License-Identifier: GPL-2.0

> + *
> + * Copyright (C) 2016-2018 EPAM Systems Inc.
> + *
> + * Author: Oleksandr Andrushchenko 
> + */
> +
> +#include 
> +
> +#include 
> +#include 
> +#include 
> +
> +#include 
> +
> +static void backend_on_changed(struct xenbus_device *xb_dev,
> + enum xenbus_state backend_state)
> +{
> +}
> +
> +static int xen_drv_probe(struct xenbus_device *xb_dev,
> + const struct xenbus_device_id *id)
> +{
> + return 0;
> +}
> +
> +static int xen_drv_remove(struct xenbus_device *dev)
> +{
> + return 0;
> +}
> +
> +static const struct xenbus_device_id xen_drv_ids[] = {
> + { XENDISPL_DRIVER_NAME },
> + { "" }
> +};
> +
> +static struct xenbus_driver xen_driver = {
> + .ids = xen_drv_ids,
> + .probe = xen_drv_probe,
> + .remove = xen_drv_remove,
> + .otherend_changed = backend_on_changed,
> +};
> +
> +static int __init xen_drv_init(void)
> +{
> + if (!xen_domain())
> + return -ENODEV;
> +
> + if (xen_initial_domain()) {
> + DRM_ERROR(XENDISPL_DRIVER_NAME " cannot run in initial 
> domain\n");
> + return -ENODEV;
> + }

Why not? Wouldn't that be possible in case of the backend living in a
driver domain?


Juergen

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

[Juergen Gross]

On 21/02/18 09:03, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko 
> 
> Introduce skeleton of the para-virtualized Xen display
> frontend driver. This patch only adds required
> essential stubs.
> 
> Signed-off-by: Oleksandr Andrushchenko 
> ---
>  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-$(CONFIG_DRM_MXSFB)   += mxsfb/
>  obj-$(CONFIG_DRM_TINYDRM) += tinydrm/
>  obj-$(CONFIG_DRM_PL111) += pl111/
>  obj-$(CONFIG_DRM_TVE200) += tve200/
> +obj-$(CONFIG_DRM_XEN) += xen/
> diff --git a/drivers/gpu/drm/xen/Kconfig b/drivers/gpu/drm/xen/Kconfig
> new file mode 100644
> index ..4cca160782ab
> --- /dev/null
> +++ b/drivers/gpu/drm/xen/Kconfig
> @@ -0,0 +1,17 @@
> +config DRM_XEN
> + bool "DRM Support for Xen guest OS"
> + depends on XEN
> + help
> +   Choose this option if you want to enable DRM support
> +   for Xen.
> +
> +config DRM_XEN_FRONTEND
> + tristate "Para-virtualized frontend driver for Xen guest OS"
> + depends on DRM_XEN
> + depends on DRM
> + select DRM_KMS_HELPER
> + select VIDEOMODE_HELPERS
> + select XEN_XENBUS_FRONTEND
> + help
> +   Choose this option if you want to enable a para-virtualized
> +   frontend DRM/KMS driver for Xen guest OSes.
> diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
> new file mode 100644
> index ..967074d348f6
> --- /dev/null
> +++ b/drivers/gpu/drm/xen/Makefile
> @@ -0,0 +1,5 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +drm_xen_front-objs := xen_drm_front.o
> +
> +obj-$(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 ..fd372fb464a1
> --- /dev/null
> +++ b/drivers/gpu/drm/xen/xen_drm_front.c
> @@ -0,0 +1,83 @@
> +/*
> + *  Xen para-virtual DRM device
> + *
> + *   This program is free software; you can redistribute it and/or modify
> + *   it under the terms of the GNU General Public License as published by
> + *   the Free Software Foundation; either version 2 of the License, or
> + *   (at your option) any later version.
> + *
> + *   This program is distributed in the hope that it will be useful,
> + *   but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *   GNU General Public License for more details.

Use SPDX identifier instead (same applies for all other new
sources):

// SPDX-License-Identifier: GPL-2.0

> + *
> + * Copyright (C) 2016-2018 EPAM Systems Inc.
> + *
> + * Author: Oleksandr Andrushchenko 
> + */
> +
> +#include 
> +
> +#include 
> +#include 
> +#include 
> +
> +#include 
> +
> +static void backend_on_changed(struct xenbus_device *xb_dev,
> + enum xenbus_state backend_state)
> +{
> +}
> +
> +static int xen_drv_probe(struct xenbus_device *xb_dev,
> + const struct xenbus_device_id *id)
> +{
> + return 0;
> +}
> +
> +static int xen_drv_remove(struct xenbus_device *dev)
> +{
> + return 0;
> +}
> +
> +static const struct xenbus_device_id xen_drv_ids[] = {
> + { XENDISPL_DRIVER_NAME },
> + { "" }
> +};
> +
> +static struct xenbus_driver xen_driver = {
> + .ids = xen_drv_ids,
> + .probe = xen_drv_probe,
> + .remove = xen_drv_remove,
> + .otherend_changed = backend_on_changed,
> +};
> +
> +static int __init xen_drv_init(void)
> +{
> + if (!xen_domain())
> + return -ENODEV;
> +
> + if (xen_initial_domain()) {
> + DRM_ERROR(XENDISPL_DRIVER_NAME " cannot run in initial 
> domain\n");
> + return -ENODEV;
> + }

Why not? Wouldn't that be possible in case of the backend living in a
driver domain?


Juergen