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

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

On 23-06-01, Ahmad Fatoum wrote:
> 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. 

Sure.

> >> 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

This should be checked earlier or do I miss something?

> cdev GPT partition not existing,despite backend pointing at root device -> -EINVAL

So this could follow without..

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

having it within the if. The cdev_find_child_by_gpt_typeuuid() could
return NULL in case nothing is found. But that's just a minor nit.

Regards,
  Marco

> 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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