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

From: Juergen Gross
Date: Wed Feb 21 2018 - 03:20:02 EST


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-$(CONFIG_DRM_MXSFB) += mxsfb/
> obj-$(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.

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 <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,
> + 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