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Date:   Wed, 21 Feb 2018 09:17:51 +0000
From:   Roger Pau =?iso-8859-1?Q?Monn=E9?= <roger.pau@citrix.com>
To:     Oleksandr Andrushchenko <andr2000@gmail.com>
CC:     <xen-devel@lists.xenproject.org>, <linux-kernel@vger.kernel.org>,
        <dri-devel@lists.freedesktop.org>, <airlied@linux.ie>,
        <daniel.vetter@intel.com>, <seanpaul@chromium.org>,
        <gustavo@padovan.org>, <jgross@suse.com>,
        <boris.ostrovsky@oracle.com>, <konrad.wilk@oracle.com>,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Subject: Re: [Xen-devel] [PATCH 1/9] drm/xen-front: Introduce Xen
 para-virtualized frontend driver
Message-ID: <20180221091751.ebczu3kzv6j7zykp@MacBook-Pro-de-Roger.local>
References: <1519200222-20623-1-git-send-email-andr2000@gmail.com>
 <1519200222-20623-2-git-send-email-andr2000@gmail.com>
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On Wed, Feb 21, 2018 at 10:03:34AM +0200, Oleksandr Andrushchenko wrote:
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> 
> Introduce skeleton of the para-virtualized Xen display
> frontend driver. This patch only adds required
> essential stubs.
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
> ---
>  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-$(CONFIG_DRM_XEN) += xen/
> diff --git a/drivers/gpu/drm/xen/Kconfig b/drivers/gpu/drm/xen/Kconfig
> new file mode 100644
> index 000000000000..4cca160782ab
> --- /dev/null
> +++ b/drivers/gpu/drm/xen/Kconfig
> @@ -0,0 +1,17 @@
> +config DRM_XEN
> +	bool "DRM Support for Xen guest OS"
> +	depends on XEN
> +	help
> +	  Choose this option if you want to enable DRM support
> +	  for Xen.
> +
> +config DRM_XEN_FRONTEND
> +	tristate "Para-virtualized frontend driver for Xen guest OS"
> +	depends on DRM_XEN
> +	depends on DRM
> +	select DRM_KMS_HELPER
> +	select VIDEOMODE_HELPERS
> +	select XEN_XENBUS_FRONTEND
> +	help
> +	  Choose this option if you want to enable a para-virtualized
> +	  frontend DRM/KMS driver for Xen guest OSes.
> diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
> new file mode 100644
> index 000000000000..967074d348f6
> --- /dev/null
> +++ b/drivers/gpu/drm/xen/Makefile
> @@ -0,0 +1,5 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +drm_xen_front-objs := xen_drm_front.o
> +
> +obj-$(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 @@
> +/*
> + *  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.

Most Xen drivers in Linux use a dual GPL/BSD license, so that they can
be imported into other non GPL OSes:

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License version 2
as published by the Free Software Foundation; or, when distributed
separately from the Linux kernel or incorporated into other
software packages, subject to the following license:

Permission is hereby granted, free of charge, to any person obtaining a copy
of this source file (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use, copy, modify,
merge, publish, distribute, sublicense, and/or sell copies of the Software,
and to permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
IN THE SOFTWARE.

IMO it would be good to release this driver under the same license, so
it can be incorporated into other OSes.

Thanks, Roger.