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    Subject[PATCH 3/9] drm/xen-front: Read driver configuration from Xen store
    Date
    From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

    Read configuration values from Xen store according
    to xen/interface/io/displif.h protocol:
    - read connector(s) configuration
    - read buffer allocation mode (backend/frontend)

    Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
    ---
    drivers/gpu/drm/xen/Makefile | 3 +-
    drivers/gpu/drm/xen/xen_drm_front.c | 9 ++++
    drivers/gpu/drm/xen/xen_drm_front.h | 3 ++
    drivers/gpu/drm/xen/xen_drm_front_cfg.c | 84 +++++++++++++++++++++++++++++++++
    drivers/gpu/drm/xen/xen_drm_front_cfg.h | 45 ++++++++++++++++++
    5 files changed, 143 insertions(+), 1 deletion(-)
    create mode 100644 drivers/gpu/drm/xen/xen_drm_front_cfg.c
    create mode 100644 drivers/gpu/drm/xen/xen_drm_front_cfg.h

    diff --git a/drivers/gpu/drm/xen/Makefile b/drivers/gpu/drm/xen/Makefile
    index 967074d348f6..0a2eae757f0c 100644
    --- a/drivers/gpu/drm/xen/Makefile
    +++ b/drivers/gpu/drm/xen/Makefile
    @@ -1,5 +1,6 @@
    # SPDX-License-Identifier: GPL-2.0

    -drm_xen_front-objs := xen_drm_front.o
    +drm_xen_front-objs := xen_drm_front.o \
    + xen_drm_front_cfg.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
    index d0306f9d660d..0a90c474c7ce 100644
    --- a/drivers/gpu/drm/xen/xen_drm_front.c
    +++ b/drivers/gpu/drm/xen/xen_drm_front.c
    @@ -32,6 +32,15 @@ static void xen_drv_remove_internal(struct xen_drm_front_info *front_info)

    static int backend_on_initwait(struct xen_drm_front_info *front_info)
    {
    + struct xen_drm_front_cfg *cfg = &front_info->cfg;
    + int ret;
    +
    + cfg->front_info = front_info;
    + ret = xen_drm_front_cfg_card(front_info, cfg);
    + if (ret < 0)
    + return ret;
    +
    + DRM_INFO("Have %d conector(s)\n", cfg->num_connectors);
    return 0;
    }

    diff --git a/drivers/gpu/drm/xen/xen_drm_front.h b/drivers/gpu/drm/xen/xen_drm_front.h
    index 8af46850f126..62b0d4e3e12b 100644
    --- a/drivers/gpu/drm/xen/xen_drm_front.h
    +++ b/drivers/gpu/drm/xen/xen_drm_front.h
    @@ -19,8 +19,11 @@
    #ifndef __XEN_DRM_FRONT_H_
    #define __XEN_DRM_FRONT_H_

    +#include "xen_drm_front_cfg.h"
    +
    struct xen_drm_front_info {
    struct xenbus_device *xb_dev;
    + struct xen_drm_front_cfg cfg;
    };

    #endif /* __XEN_DRM_FRONT_H_ */
    diff --git a/drivers/gpu/drm/xen/xen_drm_front_cfg.c b/drivers/gpu/drm/xen/xen_drm_front_cfg.c
    new file mode 100644
    index 000000000000..58fe50bc52a5
    --- /dev/null
    +++ b/drivers/gpu/drm/xen/xen_drm_front_cfg.c
    @@ -0,0 +1,84 @@
    +/*
    + * 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.
    + *
    + * Copyright (C) 2016-2018 EPAM Systems Inc.
    + *
    + * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
    + */
    +
    +#include <drm/drmP.h>
    +
    +#include <linux/device.h>
    +
    +#include <xen/interface/io/displif.h>
    +#include <xen/xenbus.h>
    +
    +#include "xen_drm_front.h"
    +#include "xen_drm_front_cfg.h"
    +
    +static int cfg_connector(struct xen_drm_front_info *front_info,
    + struct xen_drm_front_cfg_connector *connector,
    + const char *path, int index)
    +{
    + char *connector_path;
    +
    + connector_path = devm_kasprintf(&front_info->xb_dev->dev,
    + GFP_KERNEL, "%s/%d", path, index);
    + if (!connector_path)
    + return -ENOMEM;
    +
    + connector->xenstore_path = connector_path;
    + if (xenbus_scanf(XBT_NIL, connector_path, XENDISPL_FIELD_RESOLUTION,
    + "%d" XENDISPL_RESOLUTION_SEPARATOR "%d",
    + &connector->width, &connector->height) < 0) {
    + /* either no entry configured or wrong resolution set */
    + connector->width = 0;
    + connector->height = 0;
    + return -EINVAL;
    + }
    +
    + DRM_INFO("Connector %s: resolution %dx%d\n",
    + connector_path, connector->width, connector->height);
    + return 0;
    +}
    +
    +int xen_drm_front_cfg_card(struct xen_drm_front_info *front_info,
    + struct xen_drm_front_cfg *cfg)
    +{
    + struct xenbus_device *xb_dev = front_info->xb_dev;
    + int ret, i;
    +
    + if (xenbus_read_unsigned(front_info->xb_dev->nodename,
    + XENDISPL_FIELD_BE_ALLOC, 0)) {
    + DRM_INFO("Backend can provide display buffers\n");
    + cfg->be_alloc = true;
    + }
    +
    + cfg->num_connectors = 0;
    + for (i = 0; i < ARRAY_SIZE(cfg->connectors); i++) {
    + ret = cfg_connector(front_info,
    + &cfg->connectors[i], xb_dev->nodename, i);
    + if (ret < 0)
    + break;
    + cfg->num_connectors++;
    + }
    +
    + if (!cfg->num_connectors) {
    + DRM_ERROR("No connector(s) configured at %s\n",
    + xb_dev->nodename);
    + return -ENODEV;
    + }
    +
    + return 0;
    +}
    +
    diff --git a/drivers/gpu/drm/xen/xen_drm_front_cfg.h b/drivers/gpu/drm/xen/xen_drm_front_cfg.h
    new file mode 100644
    index 000000000000..1ac4948a13e5
    --- /dev/null
    +++ b/drivers/gpu/drm/xen/xen_drm_front_cfg.h
    @@ -0,0 +1,45 @@
    +/*
    + * 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.
    + *
    + * Copyright (C) 2016-2018 EPAM Systems Inc.
    + *
    + * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
    + */
    +
    +#ifndef __XEN_DRM_FRONT_CFG_H_
    +#define __XEN_DRM_FRONT_CFG_H_
    +
    +#include <linux/types.h>
    +
    +#define XEN_DRM_FRONT_MAX_CRTCS 4
    +
    +struct xen_drm_front_cfg_connector {
    + int width;
    + int height;
    + char *xenstore_path;
    +};
    +
    +struct xen_drm_front_cfg {
    + struct xen_drm_front_info *front_info;
    + /* number of connectors in this configuration */
    + int num_connectors;
    + /* connector configurations */
    + struct xen_drm_front_cfg_connector connectors[XEN_DRM_FRONT_MAX_CRTCS];
    + /* set if dumb buffers are allocated externally on backend side */
    + bool be_alloc;
    +};
    +
    +int xen_drm_front_cfg_card(struct xen_drm_front_info *front_info,
    + struct xen_drm_front_cfg *cfg);
    +
    +#endif /* __XEN_DRM_FRONT_CFG_H_ */
    --
    2.7.4
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