Re: [OSS-Tools] [PATCH] libdt: generalize of_find_device_by_uuid for scoped lookup of all UUIDs

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

Hello Roland,

On 07.06.23 10:33, Roland Hieber wrote:
> On Mon, Jun 05, 2023 at 04:32:36PM +0200, Ahmad Fatoum wrote:
>> Despite the generic name, of_find_device_by_uuid only handled
>> ID_PART_TABLE_UUID (diskuuid) and ID_PART_ENTRY_UUID (partuuid),
>> but not ID_PART_ENTRY_TYPE (GPT Partition Type UUID).
>>
>> In preparation for doing Type UUID lookups, adjust of_find_device_by_uuid
>> to support all three types of GPT UUIDs.
>>
>> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
>> ---
>> This patch is the missing prerequisite for my GPT Type UUID series.
>> ---
>>  src/libdt.c | 30 +++++++++++++++++++-----------
>>  1 file changed, 19 insertions(+), 11 deletions(-)
>>
>> diff --git a/src/libdt.c b/src/libdt.c
>> index e54d7fb5649d..2c994c647ac9 100644
>> --- a/src/libdt.c
>> +++ b/src/libdt.c
>> @@ -2405,7 +2405,9 @@ out:
>>  	return dev;
>>  }
>>  
>> -static struct udev_device *of_find_device_by_uuid(const char *uuid)
>> +static struct udev_device *of_find_device_by_uuid(struct udev_device *parent,
>> +						  const char *uuid,
>> +						  bool type_uuid)
>>  {
>>  	struct udev *udev;
>>  	struct udev_enumerate *enumerate;
>> @@ -2418,12 +2420,15 @@ static struct udev_device *of_find_device_by_uuid(const char *uuid)
>>  	}
>>  
>>  	enumerate = udev_enumerate_new(udev);
>> +	if (parent)
>> +		udev_enumerate_add_match_parent(enumerate, parent);
>>  	udev_enumerate_add_match_subsystem(enumerate, "block");
>>  	udev_enumerate_scan_devices(enumerate);
>>  	devices = udev_enumerate_get_list_entry(enumerate);
>>  	udev_list_entry_foreach(dev_list_entry, devices) {
>>  		const char *path, *devtype, *dev_uuid;
>>  		struct udev_device *device;
>> +		const char *property;
>>  
>>  		path = udev_list_entry_get_name(dev_list_entry);
>>  		device = udev_device_new_from_syspath(udev, path);
>> @@ -2432,16 +2437,19 @@ static struct udev_device *of_find_device_by_uuid(const char *uuid)
>>  		devtype = udev_device_get_devtype(device);
>>  		if (!devtype)
>>  			continue;
>> -		if (!strcmp(devtype, "disk")) {
>> -			dev_uuid = udev_device_get_property_value(device, "ID_PART_TABLE_UUID");
>> -			if (dev_uuid && !strcasecmp(dev_uuid, uuid))
>> -				return device;
>> -		} else if (!strcmp(devtype, "partition")) {
>> -			dev_uuid = udev_device_get_property_value(device, "ID_PART_ENTRY_UUID");
>> -			if (dev_uuid && !strcasecmp(dev_uuid, uuid))
>> -				return device;
>> -		}
>>  
>> +		if (type_uuid)
>> +			property = "ID_PART_ENTRY_TYPE";
>> +		else if (!strcmp(devtype, "disk"))
>> +			property = "ID_PART_TABLE_UUID";
>> +		else if (!strcmp(devtype, "partition"))
>> +			property = "ID_PART_ENTRY_UUID";
>> +		else
>> +			continue;
>> +
>> +		dev_uuid = udev_device_get_property_value(device, property);
>> +		if (dev_uuid && !strcasecmp(dev_uuid, uuid))
>> +			return device;
> 
> I wonder if we can't simply add a udev_enumerate_add_match_property
> above to do the filtering for us instead of iterating over the match
> entries ourselves.

I didn't know about udev_enumerate_add_match_property. Are multiple filters
OR'd or AND'd? For the !type_uuid case we need to check one or the other
property.

> But the patch is correct, so:
> Reviewed-by: Roland Hieber <rhi@pengutronix.de>

Thanks. I have applied this patch and will keep udev_enumerate_add_match_property
in mind for future rework.

Cheers,
Ahmad

> 
>>  	}
>>  	return NULL;
>>  }
>> @@ -2540,7 +2548,7 @@ int of_get_devicepath(struct device_node *partition_node, char **devpath, off_t
>>  					node->full_name);
>>  			return -ENODEV;
>>  		}
>> -		dev = of_find_device_by_uuid(uuid);
>> +		dev = of_find_device_by_uuid(NULL, uuid, false);
>>  		if (!dev) {
>>  			fprintf(stderr, "%s: cannot find device for uuid %s\n", __func__,
>>  				uuid);
>> -- 
>> 2.39.2
>>
>>
> 

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