Device hierarchy

[Leonardo Passos]

Hi all,

I am checking some code from the FreeBSD repository, and I came across a
situation that I could not explain, at least from the existing
documentation.

Looking at sys/dev/ata/ata-raid.c in the 9.1 release, I see the following
module declaration (line 4616):

static moduledata_t ata_raid_moduledata =
    { "ataraid", ata_raid_module_event_handler, NULL };
DECLARE_MODULE(ata, ata_raid_moduledata, SI_SUB_RAID, SI_ORDER_FIRST);
MODULE_VERSION(ataraid, 1);
MODULE_DEPEND(ataraid, ata, 1, 1, 1);
MODULE_DEPEND(ataraid, ad, 1, 1, 1);

The name of the module, as specified in DECLARE_MODULE, is ata, but the
name provided in the moduledata_t instance  is "ataraid". According to the
documentation of DECLARE_MODULE, the name field in the structure instance
(2nd parameter) is the official module name. So, it is correct to assume
that passing "ata" as the first parameter in DECLARE_MODULE is an error, as
it does not match "ataraid", or is it the case that such name is a "don't
care" field, as FreeBSD takes the name as given by the moduledata_t
instance?

Another weird situation appears in sys/dev/ata-isa.c (line 201):

static driver_t ata_isa_driver = {
    "ata",
    ata_isa_methods,
    sizeof(struct ata_channel),
};

DRIVER_MODULE(ata, isa, ata_isa_driver, ata_devclass, 0, 0);
MODULE_DEPEND(ata, ata, 1, 1, 1);

Here, the driver module name is set to "ata", and later, it is stated that
ata depends on ata. Is the dependency referring to another ata module, at a
different level in the driver stacking? How are these names and
dependencies resolved?

Thanks,

Leonardo.