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 <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>
>>> ---
>>> Â drivers/gpu/drm/KconfigÂÂÂÂÂÂÂÂÂÂÂÂ |Â 2 +
>>> Â drivers/gpu/drm/MakefileÂÂÂÂÂÂÂÂÂÂÂ |Â 1 +
>>> Â drivers/gpu/drm/xen/KconfigÂÂÂÂÂÂÂÂ | 17 ++++++++
>>> Â drivers/gpu/drm/xen/MakefileÂÂÂÂÂÂÂ |Â 5 +++
>>> Â drivers/gpu/drm/xen/xen_drm_front.c | 83
>>> +++++++++++++++++++++++++++++++++++++
>>> Â 5 files changed, 108 insertions(+)
>>> Â create mode 100644 drivers/gpu/drm/xen/Kconfig
>>> Â create mode 100644 drivers/gpu/drm/xen/Makefile
>>> Â 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"
>>> Â Â source "drivers/gpu/drm/tve200/Kconfig"
>>> Â +source "drivers/gpu/drm/xen/Kconfig"
>>> +
>>> Â # Keep legacy drivers last
>>> Â Â 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-$(CONFIG_DRM_MXSFB)ÂÂÂ += mxsfb/
>>> Â obj-$(CONFIG_DRM_TINYDRM) += tinydrm/
>>> Â obj-$(CONFIG_DRM_PL111) += pl111/
>>> Â obj-$(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.


Juergen