[PATCH v2 19/19] state: allow lookup of barebox state partition by Type GUID

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

The backend device tree property so far always pointed at a partition.
Let's allow pointing it at GPT storage devices directly and lookup
the correct barebox state partition by the well-known type GUID:

  4778ed65-bf42-45fa-9c5b-287a1dc4aab1

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
v1 -> v2:
  - fix typo (Sascha)
  - use new cdev_find_child_by_gpt_typeuuid() to make barebox-state
    code more concise (Marco)
---
 common/state/state.c | 16 ++++++++++++++++
 include/driver.h     | 19 +++++++++++++++++++
 include/state.h      |  4 ++++
 3 files changed, 39 insertions(+)

diff --git a/common/state/state.c b/common/state/state.c
index 88e246198fb8..9940a91fe34c 100644
--- a/common/state/state.c
+++ b/common/state/state.c
@@ -21,8 +21,10 @@
 #include <fs.h>
 #include <crc.h>
 #include <init.h>
+#include <block.h>
 #include <linux/err.h>
 #include <linux/list.h>
+#include <linux/uuid.h>
 
 #include <linux/mtd/mtd-abi.h>
 #include <malloc.h>
@@ -595,6 +597,8 @@ static char *cdev_to_devpath(struct cdev *cdev, off_t *offset, size_t *size)
 }
 #endif
 
+static guid_t barebox_state_partition_guid = BAREBOX_STATE_PARTITION_GUID;
+
 /*
  * state_new_from_node - create a new state instance from a device_node
  *
@@ -641,6 +645,18 @@ struct state *state_new_from_node(struct device_node *node, bool readonly)
 		goto out_release_state;
 	}
 
+	/* Is the backend referencing an on-disk partitionable block device? */
+	if (cdev_is_block_disk(cdev)) {
+		cdev = cdev_find_child_by_gpt_typeuuid(cdev, &barebox_state_partition_guid);
+		if (IS_ERR(cdev)) {
+			ret = -EINVAL;
+			goto out_release_state;
+		}
+
+		pr_debug("%s: backend GPT partition looked up via PartitionTypeGUID\n",
+			 node->full_name);
+	}
+
 	state->backend_path = cdev_to_devpath(cdev, &offset, &size);
 
 	pr_debug("%s: backend resolved to %s\n", node->full_name, state->backend_path);
diff --git a/include/driver.h b/include/driver.h
index 817e9e386bc6..d012cd006dcb 100644
--- a/include/driver.h
+++ b/include/driver.h
@@ -585,6 +585,9 @@ extern struct list_head cdev_list;
 #define for_each_cdev(cdev) \
 	list_for_each_entry((cdev), &cdev_list, list)
 
+#define for_each_cdev_partition(partcdev, cdev) \
+	list_for_each_entry((partcdev), &(cdev)->partitions, partition_entry)
+
 #define DEVFS_PARTITION_FIXED		(1U << 0)
 #define DEVFS_PARTITION_READONLY	(1U << 1)
 #define DEVFS_IS_CHARACTER_DEV		(1U << 3)
@@ -604,6 +607,22 @@ static inline bool cdev_is_gpt_partitioned(const struct cdev *master)
 	return master && (master->flags & DEVFS_IS_GPT_PARTITIONED);
 }
 
+static inline struct cdev *
+cdev_find_child_by_gpt_typeuuid(struct cdev *cdev, guid_t *typeuuid)
+{
+	struct cdev *partcdev;
+
+	if (!cdev_is_gpt_partitioned(cdev))
+		return ERR_PTR(-EINVAL);
+
+	for_each_cdev_partition(partcdev, cdev) {
+		if (guid_equal(&partcdev->typeuuid, typeuuid))
+			return partcdev;
+	}
+
+	return ERR_PTR(-ENOENT);
+}
+
 struct cdev *devfs_add_partition(const char *devname, loff_t offset,
 		loff_t size, unsigned int flags, const char *name);
 int devfs_del_partition(const char *name);
diff --git a/include/state.h b/include/state.h
index bffcd5a9007f..3daf82c0735f 100644
--- a/include/state.h
+++ b/include/state.h
@@ -62,4 +62,8 @@ static inline int state_read_mac(struct state *state, const char *name, u8 *buf)
 
 #endif /* #if IS_ENABLED(CONFIG_STATE) / #else */
 
+#define BAREBOX_STATE_PARTITION_GUID \
+	GUID_INIT(0x4778ed65, 0xbf42, 0x45fa, 0x9c, 0x5b, \
+		 0x28, 0x7a, 0x1d, 0xc4, 0xaa, 0xb1)
+
 #endif /* __STATE_H */
-- 
2.39.2