From: Petr Tesarik <ptesarik@suse.cz>
To: kbd@lists.altlinux.org
Cc: Alexey Gladkov <gladkov.alexey@gmail.com>
Subject: Re: [kbd] [PATCH] setleds: add option to reset state to the BIOS default
Date: Fri, 27 Jul 2012 09:05:46 +0200
Message-ID: <201207270905.46719.ptesarik@suse.cz> (raw)
In-Reply-To: <201207262149.05758.ptesarik@suse.cz>
Dne Čt 26. července 2012 21:49:05 Petr Tesarik napsal(a):
> Hello Alexey and everybody,
>
> please consider the following patch for kbd.
>[...]
> + bios_state = map[BIOS_KBD_ADDR - mapoff];
> + *cur_leds = 0;
> + if (bios_state & BIOS_LED_SCR)
> + *cur_leds |= LED_SCR;
> + if (bios_state & BIOS_LED_NUM)
> + *cur_leds |= LED_NUM;
> + if (bios_state & BIOS_LED_CAP)
> + *cur_leds |= LED_CAP;
I've just noticed that this produces crappy code, especially given that the
BIOS bits are numerically equal to the kernel bits, so a simple bitwise AND
would be sufficient. Rewriting the series of conditionals into one expression
allows GCC to optimize it:
*cur_leds =
(bios_state & BIOS_LED_SCR ? LED_SCR : 0) |
(bios_state & BIOS_LED_NUM ? LED_NUM : 0) |
(bios_state & BIOS_LED_CAP ? LED_CAP : 0);
Let me resend v2 of the patch,
Petr Tesarik
prev parent reply other threads:[~2012-07-27 7:05 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-26 19:49 Petr Tesarik
2012-07-27 7:05 ` Petr Tesarik [this message]
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