Re: Regarding module init function

[Dave Hylands]

Hi Tobais,

On Thu, Jan 10, 2013 at 9:47 AM, Tobias Boege  wrote:
> On Tue, 08 Jan 2013, anish kumar wrote:
> > On Tue, 2013-01-08 at 14:51 +0100, Tobias Boege wrote:
...snip...
> > > On Tue, 08 Jan 2013, Rahul Bedarkar wrote:
> > > It's, too, in the init.h. There are two definitions of module_init()
> > > depending on whether MODULE is declared or not. The first definition
is
> > How does the individual driver define this MODULE?I think some macro
> > magic works here.
>
> I suppose that this is done through the invocation of the preprocessor,
> using -DMODULE depending on whether the target is built-in or a module.

Exactly.

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Re: Regarding module init function

[Tobias Boege]

On Tue, 08 Jan 2013, anish kumar wrote:
> On Tue, 2013-01-08 at 14:51 +0100, Tobias Boege wrote:
> > On Tue, 08 Jan 2013, Rahul Bedarkar wrote:
> > > Ok. in init/main.c we call do_basic_setup(). Where do_initcalls call each
> > > of init functions from __early_initcall_end to __initcall_end. But I don't
> > > know from where these values gets initialized.
> > > 
> > 
> > Take a look at include/linux/init.h. There you can find the macros for
> > declaring various init functions. They all go into special sections. The
> > rest is linker magic (e.g. arch/x86/kernel/vmlinux.lds{,.S}).
> > 
> > > I want to know when one of auxdriver (selected in from menuconfig) is 
> > > built
> > > as built-in module. When and Who calls it's init function ?
> > 
> > It's, too, in the init.h. There are two definitions of module_init()
> > depending on whether MODULE is declared or not. The first definition is
> How does the individual driver define this MODULE?I think some macro
> magic works here.

I suppose that this is done through the invocation of the preprocessor,
using -DMODULE depending on whether the target is built-in or a module.

Regards,
Tobi


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Re: Regarding module init function

[anish kumar]

On Tue, 2013-01-08 at 14:51 +0100, Tobias Boege wrote:
> On Tue, 08 Jan 2013, Rahul Bedarkar wrote:
> > Ok. in init/main.c we call do_basic_setup(). Where do_initcalls call each
> > of init functions from __early_initcall_end to __initcall_end. But I don't
> > know from where these values gets initialized.
> > 
> 
> Take a look at include/linux/init.h. There you can find the macros for
> declaring various init functions. They all go into special sections. The
> rest is linker magic (e.g. arch/x86/kernel/vmlinux.lds{,.S}).
> 
> > I want to know when one of auxdriver (selected in from menuconfig) is built
> > as built-in module. When and Who calls it's init function ?
> 
> It's, too, in the init.h. There are two definitions of module_init()
> depending on whether MODULE is declared or not. The first definition is
How does the individual driver define this MODULE?I think some macro
magic works here.
> accompanied by a useful comment about where the init function is called in
> either case.
> 
> Regards,
> Tobi
> 
> 
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Re: Regarding module init function

[Dave Hylands]

Hi Rahul,


On Tue, Jan 8, 2013 at 2:50 PM, Rahul Bedarkar  wrote:
>
> Thanks Dave!
>
> I just verified that from System.map. Between __early_initcall_end and
__initcall_end, there is list of init calls with levels from 0-7. What is
significance of these levels.

The levels basically just control the order that the initcalls are made.
Basically, all level 0 functions are called befor level 1 functions, etc.

The meaning behind the levels can be discerned from the macros in init.h
http://lxr.linux.no/#linux+v3.7.1/include/linux/init.h#L207

There is also some docs here:
http://lxr.linux.no/#linux+v3.7.1/Documentation/DocBook/kernel-hacking.tmpl#L736

Dave Hylands
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Re: Regarding module init function

[Tobias Boege]

On Tue, 08 Jan 2013, Rahul Bedarkar wrote:
> Ok. in init/main.c we call do_basic_setup(). Where do_initcalls call each
> of init functions from __early_initcall_end to __initcall_end. But I don't
> know from where these values gets initialized.
> 

Take a look at include/linux/init.h. There you can find the macros for
declaring various init functions. They all go into special sections. The
rest is linker magic (e.g. arch/x86/kernel/vmlinux.lds{,.S}).

> I want to know when one of auxdriver (selected in from menuconfig) is built
> as built-in module. When and Who calls it's init function ?

It's, too, in the init.h. There are two definitions of module_init()
depending on whether MODULE is declared or not. The first definition is
accompanied by a useful comment about where the init function is called in
either case.

Regards,
Tobi


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Re: Regarding module init function

[Rahul Bedarkar]

Thanks Dave!

I just verified that from System.map. Between __early_initcall_end
and __initcall_end, there is list of init calls with levels from 0-7. What
is significance of these levels.

Thanks,
Rahul

On Tue, Jan 8, 2013 at 7:01 PM, Dave Hylands  wrote:

> Hi,
>
>
>
> On Tue, Jan 8, 2013 at 11:08 AM, Rahul Bedarkar  wrote:
> >
> > Ok. in init/main.c we call do_basic_setup(). Where do_initcalls call
> each of init functions from __early_initcall_end to __initcall_end. But I
> don't know from where these values gets initialized.
>
> If you look here:
> http://lxr.linux.no/#linux+v3.7.1/include/linux/init.h#L279
>
> module_init is mapped to __initcall, which is in turn mapped to
> device_initcall, which sets up a pointer in a section called .initcall6.init
>
> If you then look in the kernel linker script:
> http://lxr.linux.no/#linux+v3.7.1/arch/arm/kernel/vmlinux.lds.S#L175
>
> INIT_CALLS is defined here:
> http://lxr.linux.no/#linux+v3.7.1/include/asm-generic/vmlinux.lds.h#L633
>
> and it defines the __initcall_start and __initcall_end symbols.
>
> Dave Hylands
>
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Re: Regarding module init function

[Dave Hylands]

Hi,


On Tue, Jan 8, 2013 at 11:08 AM, Rahul Bedarkar  wrote:
>
> Ok. in init/main.c we call do_basic_setup(). Where do_initcalls call each
of init functions from __early_initcall_end to __initcall_end. But I don't
know from where these values gets initialized.

If you look here:
http://lxr.linux.no/#linux+v3.7.1/include/linux/init.h#L279

module_init is mapped to __initcall, which is in turn mapped to
device_initcall, which sets up a pointer in a section called .initcall6.init

If you then look in the kernel linker script:
http://lxr.linux.no/#linux+v3.7.1/arch/arm/kernel/vmlinux.lds.S#L175

INIT_CALLS is defined here:
http://lxr.linux.no/#linux+v3.7.1/include/asm-generic/vmlinux.lds.h#L633

and it defines the __initcall_start and __initcall_end symbols.

Dave Hylands
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Re: Regarding module init function

[Rahul Bedarkar]

Ok. in init/main.c we call do_basic_setup(). Where do_initcalls call each
of init functions from __early_initcall_end to __initcall_end. But I don't
know from where these values gets initialized.

On Tue, Jan 8, 2013 at 2:10 PM, Rahul Bedarkar  wrote:

> I have gone through LDD3 page 31. But it didn't answer my question. It
> is describing module init and exit when manually loading driver and
> removing it.
> I want to know when one of auxdriver (selected in from menuconfig) is
> built as built-in module. When and Who calls it's init function ?
>
> Thanks,
> Rahul
>
> On Fri, Jan 4, 2013 at 6:52 PM, Tobias Boege wrote:
>
>> On Fri, 04 Jan 2013, Rahul Bedarkar wrote:
>> > Hi,
>> >
>> > This may be stupid question.
>> >
>> > When we compile external module and insert it, it's init function is
>> called
>> > and when we remove it, it's exit function gets called.
>> >
>> > What happens in case of built-in modules? When it's init and exit is
>> > called? May be take example of one of auxdriver.
>> >
>>
>> You can find relevant information in LDD3, pp. 31 ff.. Basically, there is
>> no difference in the use of the init function (it's called at kernel
>> startup, I suppose) but exit is simply discarded in this case, because if
>> your module is built-in, it could never be removed.
>>
>> Regards,
>> Tobi
>>
>>
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>
>
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Re: Regarding module init function

[Rahul Bedarkar]

I have gone through LDD3 page 31. But it didn't answer my question. It
is describing module init and exit when manually loading driver and
removing it.
I want to know when one of auxdriver (selected in from menuconfig) is built
as built-in module. When and Who calls it's init function ?

Thanks,
Rahul

On Fri, Jan 4, 2013 at 6:52 PM, Tobias Boege  wrote:

> On Fri, 04 Jan 2013, Rahul Bedarkar wrote:
> > Hi,
> >
> > This may be stupid question.
> >
> > When we compile external module and insert it, it's init function is
> called
> > and when we remove it, it's exit function gets called.
> >
> > What happens in case of built-in modules? When it's init and exit is
> > called? May be take example of one of auxdriver.
> >
>
> You can find relevant information in LDD3, pp. 31 ff.. Basically, there is
> no difference in the use of the init function (it's called at kernel
> startup, I suppose) but exit is simply discarded in this case, because if
> your module is built-in, it could never be removed.
>
> Regards,
> Tobi
>
>
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Re: Regarding module init function

[Tobias Boege]

On Fri, 04 Jan 2013, Rahul Bedarkar wrote:
> Hi,
> 
> This may be stupid question.
> 
> When we compile external module and insert it, it's init function is called
> and when we remove it, it's exit function gets called.
> 
> What happens in case of built-in modules? When it's init and exit is
> called? May be take example of one of auxdriver.
> 

You can find relevant information in LDD3, pp. 31 ff.. Basically, there is
no difference in the use of the init function (it's called at kernel
startup, I suppose) but exit is simply discarded in this case, because if
your module is built-in, it could never be removed.

Regards,
Tobi


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Regarding module init function

[Rahul Bedarkar]

Hi,

This may be stupid question.

When we compile external module and insert it, it's init function is called
and when we remove it, it's exit function gets called.

What happens in case of built-in modules? When it's init and exit is
called? May be take example of one of auxdriver.


Thanks,
Rahul
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