!! 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@yahoo.cn

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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@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@kernelnewbies.org is one of them. Hope that helps, Jonathan Neuschäfer