Re: [PATCH 18/18] state: allow lookup of barebox state partition by Type GUID

[Marco Felsch <m.felsch@pengutronix.de>]

Hi Ahmad,

On 23-05-31, Ahmad Fatoum wrote:
> 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

we should add an example within the Documetation/ too.

> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  common/state/state.c | 22 ++++++++++++++++++++++
>  include/driver.h     | 17 +++++++++++++++++
>  include/state.h      |  4 ++++
>  3 files changed, 43 insertions(+)
> 
> diff --git a/common/state/state.c b/common/state/state.c
> index 88e246198fb8..8f56c60b0e82 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 +645,24 @@ struct state *state_new_from_node(struct device_node *node, bool readonly)
>  		goto out_release_state;
>  	}
>  
> +	/* Is the backend referencing an on-disk partitonable block device? */
> +	if (cdev_is_block_disk(cdev)) {
> +		struct cdev *partcdev = NULL;
> +
> +		if (cdev_is_gpt_partitioned(cdev))
> +			partcdev = cdev_find_child_by_typeuuid(cdev, &barebox_state_partition_guid);
> +
> +		if (!partcdev) {
> +			ret = -EINVAL;
> +			goto out_release_state;
> +		}
> +
> +		pr_debug("%s: backend GPT partition looked up via PartitionTypeGUID\n",
> +			 node->full_name);
> +
> +		cdev = partcdev;
> +	}

What about having the above logic within a seperate function and the
above code would be:

	if (cdev_is_block_disk(cdev))
		cdev = get_cdev_by_typeuuid(cdev, &barebox_state_partition_guid)
	
	if (!cdev) {
		ret = -EINVAL;
		goto out_release_state;
	}

This way we would have everything in place to re-use the same logic for
the barebox-environmnet too. What do you think?

Regards,
  Marco

> +
>  	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 6407f7d6ba36..579b03fbac34 100644
> --- a/include/driver.h
> +++ b/include/driver.h
> @@ -585,6 +585,23 @@ 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)
> +
> +
> +static inline struct cdev *cdev_find_child_by_typeuuid(struct cdev *cdev,
> +						       guid_t *typeuuid)
> +{
> +	struct cdev *partcdev;
> +
> +	for_each_cdev_partition(partcdev, cdev) {
> +		if (guid_equal(&partcdev->typeuuid, typeuuid))
> +			return partcdev;
> +	}
> +
> +	return NULL;
> +}
> +
>  #define DEVFS_PARTITION_FIXED		(1U << 0)
>  #define DEVFS_PARTITION_READONLY	(1U << 1)
>  #define DEVFS_IS_CHARACTER_DEV		(1U << 3)
> 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
> 
> 
>