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From: Petr Tesarik <ptesarik@suse.cz>
Organization: SUSE LINUX, s.r.o.
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Date: Fri, 27 Jul 2012 09:05:46 +0200
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Cc: Alexey Gladkov <gladkov.alexey@gmail.com>
Subject: Re: [kbd] [PATCH] setleds: add option to reset state to the BIOS
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Dne =C4=8Ct 26. =C4=8Dervence 2012 21:49:05 Petr Tesarik napsal(a):
> Hello Alexey and everybody,
>=20
> please consider the following patch for kbd.
>[...]
> +    bios_state =3D map[BIOS_KBD_ADDR - mapoff];
> +    *cur_leds =3D 0;
> +    if (bios_state & BIOS_LED_SCR)
> +	*cur_leds |=3D LED_SCR;
> +    if (bios_state & BIOS_LED_NUM)
> +	*cur_leds |=3D LED_NUM;
> +    if (bios_state & BIOS_LED_CAP)
> +	*cur_leds |=3D LED_CAP;

I've just noticed that this produces crappy code, especially given that the=
=20
BIOS bits are numerically equal to the kernel bits, so a simple bitwise AND=
=20
would be sufficient. Rewriting the series of conditionals into one expressi=
on=20
allows GCC to optimize it:

    *cur_leds =3D
        (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