Date: Sat, 14 Sep 2013 11:25:37 -0700 From: John-Mark Gurney <jmg@funkthat.com> To: Leonardo Passos <lnrdpss@gmail.com> Cc: freebsd-drivers@freebsd.org Subject: Re: Device hierarchy Message-ID: <20130914182537.GZ68682@funkthat.com> In-Reply-To: <CAO10wb6_AoZ9maGhx326tjZ6-aqvyzVV7rBxfOv%2BLOABixs_cw@mail.gmail.com> References: <CAO10wb6_AoZ9maGhx326tjZ6-aqvyzVV7rBxfOv%2BLOABixs_cw@mail.gmail.com>
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Leonardo Passos wrote this message on Sat, Sep 14, 2013 at 14:09 -0400:
> 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);
Read below, it looks like DECLARE_MODULE's name is the same:
#define DECLARE_MODULE_WITH_MAXVER(name, data, sub, order, maxver) \
MODULE_DEPEND(name, kernel, __FreeBSD_version, \
__FreeBSD_version, maxver); \
MODULE_METADATA(_md_##name, MDT_MODULE, &data, #name); \
SYSINIT(name##module, sub, order, module_register_init, &data); \
struct __hack
#define DECLARE_MODULE(name, data, sub, order) \
DECLARE_MODULE_WITH_MAXVER(name, data, sub, order, MODULE_KERNEL_MAXVER)
and the first arg to SYSINIT is uniquifier...
> 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?
Here, MODULE_DEPEND should probably be:
MODULE_DEPEND(isa/ata, ata, 1, 1, 1);
but I'm not sure how that would/will work... Here DRIVER_MODULE does
something special and names the module w/ the bus/name instead of just
the first one, and why if you run kldstat -v, you'll see something like:
45 isa/ata
in the output... But after looking at the MODULE_DEPEND, what really
matters is that the first arg is unique per file since the macro only
uses it to name symbols:
#define MODULE_METADATA(uniquifier, type, data, cval) \
static struct mod_metadata _mod_metadata##uniquifier = { \
MDT_STRUCT_VERSION, \
type, \
data, \
cval \
}; \
DATA_SET(modmetadata_set, _mod_metadata##uniquifier)
#define MODULE_DEPEND(module, mdepend, vmin, vpref, vmax) \
static struct mod_depend _##module##_depend_on_##mdepend = { \
vmin, \
vpref, \
vmax \
}; \
MODULE_METADATA(_md_##module##_on_##mdepend, MDT_DEPEND, \
&_##module##_depend_on_##mdepend, #mdepend)
So, adding the slash is probably not useful... It should probably be
made clear in MODULE_DEPEND that name is only used to uniquify the
symbols and have no useful info... Maybe we should switch to using
__LINE__ instead, and make name option/unused?
We should probably change the first arg for MODULE_DEPEND and
DECLARE_MODULE to be like SYSINIT's and name them uniquifier..
P.S. The macros I pasted came from sys/module.h.
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
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