xen: pvblock: Add initial support for para-virtualized block driver

Add initial infrastructure for Xen para-virtualized block device.
This includes compile-time configuration and the skeleton for
the future driver implementation.
Add new class UCLASS_PVBLOCK which is going to be a parent for
virtual block devices.
Add new interface type IF_TYPE_PVBLOCK.

Implement basic driver setup by reading XenStore configuration.

Signed-off-by: Andrii Anisov <andrii_anisov@epam.com>
Signed-off-by: Anastasiia Lukianenko <anastasiia_lukianenko@epam.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

5 files changed, 136 insertions, 0 deletions

diff --git a/drivers/Kconfig b/drivers/Kconfig
index 119e412849..613669cb38 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -136,6 +136,8 @@ source "drivers/w1-eeprom/Kconfig"
 
 source "drivers/watchdog/Kconfig"
 
+source "drivers/xen/Kconfig"
+
 config PHYS_TO_BUS
 	bool "Custom physical to bus address mapping"
 	help
diff --git a/drivers/block/blk-uclass.c b/drivers/block/blk-uclass.c
index b46a1ac8d2..2fb9f6b765 100644
--- a/drivers/block/blk-uclass.c
+++ b/drivers/block/blk-uclass.c
@@ -28,6 +28,7 @@ static const char *if_typename_str[IF_TYPE_COUNT] = {
 	[IF_TYPE_NVME]		= "nvme",
 	[IF_TYPE_EFI]		= "efi",
 	[IF_TYPE_VIRTIO]	= "virtio",
+	[IF_TYPE_PVBLOCK]	= "pvblock",
 };
 
 static enum uclass_id if_type_uclass_id[IF_TYPE_COUNT] = {
@@ -43,6 +44,7 @@ static enum uclass_id if_type_uclass_id[IF_TYPE_COUNT] = {
 	[IF_TYPE_NVME]		= UCLASS_NVME,
 	[IF_TYPE_EFI]		= UCLASS_EFI,
 	[IF_TYPE_VIRTIO]	= UCLASS_VIRTIO,
+	[IF_TYPE_PVBLOCK]	= UCLASS_PVBLOCK,
 };
 
 static enum if_type if_typename_to_iftype(const char *if_typename)
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
new file mode 100644
index 0000000000..6ad2a93668
--- /dev/null
+++ b/drivers/xen/Kconfig
@@ -0,0 +1,10 @@
+config PVBLOCK
+	bool "Xen para-virtualized block device"
+	depends on DM
+	select BLK
+	select HAVE_BLOCK_DEVICE
+	help
+	  This driver implements the front-end of the Xen virtual
+	  block device driver. It communicates with a back-end driver
+	  in another domain which drives the actual block device.
+
diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
index 243b13277a..87157df69b 100644
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -6,3 +6,5 @@ obj-y += hypervisor.o
 obj-y += events.o
 obj-y += xenbus.o
 obj-y += gnttab.o
+
+obj-$(CONFIG_PVBLOCK) += pvblock.o
diff --git a/drivers/xen/pvblock.c b/drivers/xen/pvblock.c
new file mode 100644
index 0000000000..d2b616bb63
--- /dev/null
+++ b/drivers/xen/pvblock.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2020 EPAM Systems Inc.
+ */
+#include <blk.h>
+#include <common.h>
+#include <dm.h>
+#include <dm/device-internal.h>
+
+#define DRV_NAME	"pvblock"
+#define DRV_NAME_BLK	"pvblock_blk"
+
+struct blkfront_dev {
+	char dummy;
+};
+
+static int init_blkfront(unsigned int devid, struct blkfront_dev *dev)
+{
+	return 0;
+}
+
+static void shutdown_blkfront(struct blkfront_dev *dev)
+{
+}
+
+ulong pvblock_blk_read(struct udevice *udev, lbaint_t blknr, lbaint_t blkcnt,
+		       void *buffer)
+{
+	return 0;
+}
+
+ulong pvblock_blk_write(struct udevice *udev, lbaint_t blknr, lbaint_t blkcnt,
+			const void *buffer)
+{
+	return 0;
+}
+
+static int pvblock_blk_bind(struct udevice *udev)
+{
+	return 0;
+}
+
+static int pvblock_blk_probe(struct udevice *udev)
+{
+	struct blkfront_dev *blk_dev = dev_get_priv(udev);
+	int ret;
+
+	ret = init_blkfront(0, blk_dev);
+	if (ret < 0)
+		return ret;
+	return 0;
+}
+
+static int pvblock_blk_remove(struct udevice *udev)
+{
+	struct blkfront_dev *blk_dev = dev_get_priv(udev);
+
+	shutdown_blkfront(blk_dev);
+	return 0;
+}
+
+static const struct blk_ops pvblock_blk_ops = {
+	.read	= pvblock_blk_read,
+	.write	= pvblock_blk_write,
+};
+
+U_BOOT_DRIVER(pvblock_blk) = {
+	.name			= DRV_NAME_BLK,
+	.id			= UCLASS_BLK,
+	.ops			= &pvblock_blk_ops,
+	.bind			= pvblock_blk_bind,
+	.probe			= pvblock_blk_probe,
+	.remove			= pvblock_blk_remove,
+	.priv_auto_alloc_size	= sizeof(struct blkfront_dev),
+	.flags			= DM_FLAG_OS_PREPARE,
+};
+
+/*******************************************************************************
+ * Para-virtual block device class
+ *******************************************************************************/
+
+void pvblock_init(void)
+{
+	struct driver_info info;
+	struct udevice *udev;
+	struct uclass *uc;
+	int ret;
+
+	/*
+	 * At this point Xen drivers have already initialized,
+	 * so we can instantiate the class driver and enumerate
+	 * virtual block devices.
+	 */
+	info.name = DRV_NAME;
+	ret = device_bind_by_name(gd->dm_root, false, &info, &udev);
+	if (ret < 0)
+		printf("Failed to bind " DRV_NAME ", ret: %d\n", ret);
+
+	/* Bootstrap virtual block devices class driver */
+	ret = uclass_get(UCLASS_PVBLOCK, &uc);
+	if (ret)
+		return;
+	uclass_foreach_dev_probe(UCLASS_PVBLOCK, udev);
+}
+
+static int pvblock_probe(struct udevice *udev)
+{
+	return 0;
+}
+
+U_BOOT_DRIVER(pvblock_drv) = {
+	.name		= DRV_NAME,
+	.id		= UCLASS_PVBLOCK,
+	.probe		= pvblock_probe,
+};
+
+UCLASS_DRIVER(pvblock) = {
+	.name		= DRV_NAME,
+	.id		= UCLASS_PVBLOCK,
+};