[Question] For what stand's __initdata, __devinit etc. ?

[Question] For what stand's __initdata, __devinit etc. ?

[René Bolldorf]

Hi,
Do we really need this?
It will be nice if someone can me explain this.

Thx in advance.

René

Re: [Question] For what stand's __initdata, __devinit etc. ?

[Henrique de Moraes Holschuh]

On Tue, 12 Jan 2010, René Bolldorf wrote:
> Hi,
> Do we really need this?
> It will be nice if someone can me explain this.

http://kernelnewbies.org/FAQ/InitExitMacros

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh

Re: [Question] For what stand's __initdata, __devinit etc. ?

[Tilman Schmidt]

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Am 2010-01-13 00:42 schrieb Henrique de Moraes Holschuh:
> On Tue, 12 Jan 2010, René Bolldorf wrote:
>> Hi,
>> Do we really need this?
>> It will be nice if someone can me explain this.
> 
> http://kernelnewbies.org/FAQ/InitExitMacros

That's far from complete. It does not, for example, mention __devinit.

- -- 
Tilman Schmidt                    E-Mail: tilman@imap.cc
Bonn, Germany
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Re: [Question] For what stand's __initdata, __devinit etc. ?

[Stefan Richter]

Tilman Schmidt wrote:
> Am 2010-01-13 00:42 schrieb Henrique de Moraes Holschuh:
>> On Tue, 12 Jan 2010, René Bolldorf wrote:
>>> Hi,
>>> Do we really need this?
>>> It will be nice if someone can me explain this.
>> 
>> http://kernelnewbies.org/FAQ/InitExitMacros
> 
> That's far from complete. It does not, for example, mention __devinit.

This wiki contains also somewhat misleadingly worded text:  "But why
must you use these macros ?"  This should read:  "But why would you want
to use these macros?"

Answer:  They are a micro-optimization which allows the kernel to free
memory that was occupied by this code at some point, because that code
won't be used after that point anymore.  (In case of exit macros:  These
are hints to discard some code from a build in case of certain kernel
configurations.)  These macros only affect code which is statically
linked into the kernel.

Some macros, like for example __devinit, have so obscure uses and
marginal benefits that a normal developer should not bother about them.
__devinit in particular does not have any effect at all --- except if
CONFIG_HOTPLUG is not defined.  This may happen in configurations for
embedded systems.  But the majority of device drivers that you can find
in the kernel tree are irrelevant (i.e. configured off) on such systems
anyway.

Some more information on these macros can be found in Corbet, Rubini,
Kroah-Hartman: Linux Device Drivers, 3rd edition a.k.a. LDD3, which is
also gratis available on the Web.
-- 
Stefan Richter
-=====-==-=- ---= -==-=
http://arcgraph.de/sr/

Re: [Question] For what stand's __initdata, __devinit etc. ?

[René Bolldorf]

On 01/13/10 17:37, Stefan Richter wrote:
> Tilman Schmidt wrote:
>> Am 2010-01-13 00:42 schrieb Henrique de Moraes Holschuh:
>>> On Tue, 12 Jan 2010, René Bolldorf wrote:
>>>> Hi,
>>>> Do we really need this?
>>>> It will be nice if someone can me explain this.
>>>
>>> http://kernelnewbies.org/FAQ/InitExitMacros
>>
>> That's far from complete. It does not, for example, mention __devinit.
>
> This wiki contains also somewhat misleadingly worded text:  "But why
> must you use these macros ?"  This should read:  "But why would you want
> to use these macros?"
>
> Answer:  They are a micro-optimization which allows the kernel to free
> memory that was occupied by this code at some point, because that code
> won't be used after that point anymore.  (In case of exit macros:  These
> are hints to discard some code from a build in case of certain kernel
> configurations.)  These macros only affect code which is statically
> linked into the kernel.
>
> Some macros, like for example __devinit, have so obscure uses and
> marginal benefits that a normal developer should not bother about them.
> __devinit in particular does not have any effect at all --- except if
> CONFIG_HOTPLUG is not defined.  This may happen in configurations for
> embedded systems.  But the majority of device drivers that you can find
> in the kernel tree are irrelevant (i.e. configured off) on such systems
> anyway.
>
> Some more information on these macros can be found in Corbet, Rubini,
> Kroah-Hartman: Linux Device Drivers, 3rd edition a.k.a. LDD3, which is
> also gratis available on the Web.

Thanks @all :-)