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

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

On 31.05.23 22:01, Marco Felsch wrote:
> 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.

I'd wait until we have a new dt-utils release with the same
binding. Anything else would be confusing. 

> 
>> 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?

cdev from of_cdev_find not being available -> -EPROBE_DEFER
cdev GPT partition not existing,despite backend pointing at root device -> -EINVAL

So the cdev check needs to be within if (cdev_is_block_disk(cdev)).

I don't object to combining cdev_is_gpt_partitioned and cdev_find_child_by_typeuuid into
cdev_find_child_by_gpt_typeuuid though.


Thanks for all the review!
Ahmad

> 
> 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
>>
>>
>>
> 

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