linux-kernel - Re: [PATCH 2/9] drivers/acpi/asus

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Date:	Fri, 29 Feb 2008 19:06:48 +0100
From:	Mark Pearson <devnull.port@...glemail.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Karol Kozimor <sziwan@...l.org.pl>, Julia Lawall <julia@...u.dk>,
	corentincj@...aif.net, sziwan@...rs.sourceforge.net,
	acpi4asus-user@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org, Len Brown <lenb@...nel.org>
Subject: Re: [PATCH 2/9] drivers/acpi/asus_acpi.c: Correct use of ! and &

Andrew Morton wrote:
>> Seems an odd way of doing:
>>
>> 	led_out ^= 0x01;
> 
> It does.
> 
>> It this due to some optimisation?
> 
> Surely not ;)
>
;) Thought so - one doesn't like to be too presumptuous ;)

> That code has been there for many years.
> 
> I changed the patch to this:
> 
> --- a/drivers/acpi/asus_acpi.c~drivers-acpi-asus_acpic-correct-use-of-and
> +++ a/drivers/acpi/asus_acpi.c
> @@ -610,7 +610,7 @@ write_led(const char __user * buffer, un
>  	    (led_out) ? (hotk->status | ledmask) : (hotk->status & ~ledmask);
>  
>  	if (invert)		/* invert target value */
> -		led_out = !led_out & 0x1;
> +		led_out = !led_out;
>  
>  	if (!write_acpi_int(hotk->handle, ledname, led_out, NULL))
>  		printk(KERN_WARNING "Asus ACPI: LED (%s) write failed\n",
> _
> 
> 

Is the ! operator architecture/compiler dependent? or can one always say that
!NON_ZERO_VALUE == 0 and !0 == 1?

Cheers, Mark.
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