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* what does it use two "!!"
  2013-04-01  4:12 pci_alloc_consistent doubt Avinash Patil
@ 2013-04-01  7:10 ` Ben Wu
  2013-04-01  9:37   ` Valdis.Kletnieks at vt.edu
  0 siblings, 1 reply; 6+ messages in thread
From: Ben Wu @ 2013-04-01  7:10 UTC (permalink / raw)
  To: kernelnewbies

Dear All?
1> I found some placeuse two "!!", what's means 
??? if(button->gpio != INVALID_GPIO)
??? ??? state = !!((gpio_get_value(button->gpio) ? 1 : 0) ^ button->active_low);
??? else
??? ??? state = !!button->adc_state;

2> is there some MSN group to study linux kernel or discuss it ?

Thanks and Best Regards

Ben Wu

MSN:crayben at yahoo.cn

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* what does it use two "!!"
@ 2013-04-01  7:13 Ben Wu
  2013-04-01  7:18 ` anish singh
                   ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Ben Wu @ 2013-04-01  7:13 UTC (permalink / raw)
  To: kernelnewbies



Dear All?
1> I found some placeuse two "!!", what's means 
??? if(button->gpio != INVALID_GPIO)
??? ??? state = !!((gpio_get_value(button->gpio) ? 1 : 0) ^ button->active_low);
??? else
??? ??? state = !!button->adc_state;

2> is there some MSN group to study linux kernel or discuss it ?

Thanks and Best Regards

Ben Wu

MSN:crayben at yahoo.cn

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^ permalink raw reply	[flat|nested] 6+ messages in thread
* what does it use two "!!"
  2013-04-01  7:13 what does it use two "!!" Ben Wu
@ 2013-04-01  7:18 ` anish singh
  2013-04-01 13:47 ` Christopher Harvey
  2013-04-01 23:36 ` Jonathan Neuschäfer
  2 siblings, 0 replies; 6+ messages in thread
From: anish singh @ 2013-04-01  7:18 UTC (permalink / raw)
  To: kernelnewbies

!! is generally used to make the return bool value.
You can use kernelnewbies and linux kernel mailing list.


On Mon, Apr 1, 2013 at 12:43 PM, Ben Wu <crayben@yahoo.cn> wrote:

>
>
> Dear All?
> 1> I found some placeuse two "!!", what's means
>     if(button->gpio != INVALID_GPIO)
>         state = !!((gpio_get_value(button->gpio) ? 1 : 0) ^
> button->active_low);
>     else
>         state = !!button->adc_state;
>
> 2> is there some MSN group to study linux kernel or discuss it ?
>
> Thanks and Best Regards
> Ben Wu
> MSN:crayben at yahoo.cn
>
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
>
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* what does it use two "!!"
  2013-04-01  7:10 ` what does it use two "!!" Ben Wu
@ 2013-04-01  9:37   ` Valdis.Kletnieks at vt.edu
  0 siblings, 0 replies; 6+ messages in thread
From: Valdis.Kletnieks at vt.edu @ 2013-04-01  9:37 UTC (permalink / raw)
  To: kernelnewbies

On Mon, 01 Apr 2013 15:10:46 +0800, Ben Wu said:

> 1> I found some placeuse two "!!", what's means 
>??? if(button->gpio != INVALID_GPIO)
>??? ??? state = !!((gpio_get_value(button->gpio) ? 1 : 0) ^ button->active_low);
>??? else

Gaah. That line of code fell out of the ugly tree and hit every branch
on the way down.

Use of "!!"  *and*  "? 1 :0 " in the same line of code to do the same thing.
Ouch.
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^ permalink raw reply	[flat|nested] 6+ messages in thread
* what does it use two "!!"
  2013-04-01  7:13 what does it use two "!!" Ben Wu
  2013-04-01  7:18 ` anish singh
@ 2013-04-01 13:47 ` Christopher Harvey
  2013-04-01 23:36 ` Jonathan Neuschäfer
  2 siblings, 0 replies; 6+ messages in thread
From: Christopher Harvey @ 2013-04-01 13:47 UTC (permalink / raw)
  To: kernelnewbies


Ben Wu writes:

> Dear All?
> 1> I found some placeuse two "!!", what's means 
>  if(button->gpio != INVALID_GPIO)
>   state = !!((gpio_get_value(button->gpio) ? 1 : 0) ^ button->active_low);
>  else
>   state = !!button->adc_state;

if a = 1010011 then
!a = 0 and
!!a = 1

if a = 000000 then
!a = 1
!! = 0

basically it means if a is non-zero then make a = exactly 1, else leave
it at zero.

> 2> is there some MSN group to study linux kernel or discuss it ?

don't know, but it would be ironic.

> Thanks and Best Regards
>
> Ben Wu
>
> MSN:crayben at yahoo.cn
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

^ permalink raw reply	[flat|nested] 6+ messages in thread
* what does it use two "!!"
  2013-04-01  7:13 what does it use two "!!" Ben Wu
  2013-04-01  7:18 ` anish singh
  2013-04-01 13:47 ` Christopher Harvey
@ 2013-04-01 23:36 ` Jonathan Neuschäfer
  2 siblings, 0 replies; 6+ messages in thread
From: Jonathan Neuschäfer @ 2013-04-01 23:36 UTC (permalink / raw)
  To: kernelnewbies

On Mon, Apr 01, 2013 at 03:13:06PM +0800, Ben Wu wrote:
> 2> is there some MSN group to study linux kernel or discuss it ?

> MSN:crayben at yahoo.cn

You seem to have a strange notion of "MSN". I guess you don't mean
"Microsoft Network" (which really is what MSN means much of the time),
but e-mail. If you do, then yes, there are a lot of mailing lists about
various aspects of the linux kernel, and kernelnewbies at kernelnewbies.org
is one of them.

Hope that helps,
Jonathan Neusch?fer

^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2013-04-01 23:36 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2013-04-01  7:13 what does it use two "!!" Ben Wu
2013-04-01  7:18 ` anish singh
2013-04-01 13:47 ` Christopher Harvey
2013-04-01 23:36 ` Jonathan Neuschäfer
  -- strict thread matches above, loose matches on Subject: below --
2013-04-01  4:12 pci_alloc_consistent doubt Avinash Patil
2013-04-01  7:10 ` what does it use two "!!" Ben Wu
2013-04-01  9:37   ` Valdis.Kletnieks at vt.edu

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