[PATCH v2 3/8] drm/xen-front: Read driver configuration from Xen store

[Oleksandr Andrushchenko]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko at 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 at 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 | 77 +++++++++++++++++++++++++++++++++
 drivers/gpu/drm/xen/xen_drm_front_cfg.h | 37 ++++++++++++++++
 5 files changed, 128 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 3283e104c7bb..d3ec8c8589e0 100644
--- a/drivers/gpu/drm/xen/Makefile
+++ b/drivers/gpu/drm/xen/Makefile
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0 OR MIT
 
-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 520b5b34520b..ca42ceb24a40 100644
--- a/drivers/gpu/drm/xen/xen_drm_front.c
+++ b/drivers/gpu/drm/xen/xen_drm_front.c
@@ -24,6 +24,15 @@ static void xen_drv_remove_internal(struct xen_drm_front_info *front_info)
 
 static int displback_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 8b8d4d1e0816..034a3987657e 100644
--- a/drivers/gpu/drm/xen/xen_drm_front.h
+++ b/drivers/gpu/drm/xen/xen_drm_front.h
@@ -11,8 +11,11 @@
 #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..9a0b2b8e6169
--- /dev/null
+++ b/drivers/gpu/drm/xen/xen_drm_front_cfg.c
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko at 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;
+
+	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;
+	}
+
+	connector->xenstore_path = connector_path;
+
+	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..6e7af670f8cd
--- /dev/null
+++ b/drivers/gpu/drm/xen/xen_drm_front_cfg.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko at 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