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From:   =?utf-8?Q?Bj=C3=B8rn_Mork?= <bjorn@mork.no>
To:     Eric Wong <e@80x24.org>
Cc:     Henrique de Moraes Holschuh <ibm-acpi@hmh.eng.br>,
        Shuduo Sang <shuduo.sang@canonical.com>,
        Darren Hart <dvhart@infradead.org>,
        Andy Shevchenko <andy@infradead.org>,
        linux-kernel@vger.kernel.org, ibm-acpi-devel@lists.sourceforge.net,
        platform-driver-x86@vger.kernel.org
Subject: Re: [PATCH] platform/x86: thinkpad_acpi: add adaptive_kbd_modes parameter
Organization: m
References: <20181115073429.z44czywrf7f65ndb@dcvr>
        <20181124232327.t3awc6dnjqdtvzwu@dcvr>
        <87in0l31b9.fsf@miraculix.mork.no>
        <20181125144441.xpwuov2i7lab3agh@dcvr>
Date:   Sun, 25 Nov 2018 16:41:15 +0100
In-Reply-To: <20181125144441.xpwuov2i7lab3agh@dcvr> (Eric Wong's message of
        "Sun, 25 Nov 2018 14:44:41 +0000")
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Eric Wong <e@80x24.org> writes:
> Bj=C3=B8rn Mork <bjorn@mork.no> wrote:
>
>> And then I believe you have a busy loop here:
>>=20
>> > @@ -3815,20 +3838,20 @@ static int adaptive_keyboard_set_mode(int new_=
mode)
>> >=20=20
>> >  static int adaptive_keyboard_get_next_mode(int mode)
>> >  {
>> > -	size_t i;
>> > -	size_t max_mode =3D ARRAY_SIZE(adaptive_keyboard_modes) - 1;
>> > -
>> > -	for (i =3D 0; i <=3D max_mode; i++) {
>> > -		if (adaptive_keyboard_modes[i] =3D=3D mode)
>> > -			break;
>> > -	}
>> > +	int max_mode =3D fls(adaptive_kbd_modes);
>> > +	int new_mode =3D mode >=3D max_mode ? HOME_MODE : mode + 1;
>> >=20=20
>> > -	if (i >=3D max_mode)
>> > -		i =3D 0;
>> > -	else
>> > -		i++;
>> > +	/* make sure the new mode is allowed by the user */
>> > +	while (!(adaptive_kbd_modes & (1 << new_mode))) {
>> > +		new_mode++;
>> > +		if (new_mode > max_mode)
>> > +			new_mode =3D HOME_MODE;
>> >=20=20
>> > -	return adaptive_keyboard_modes[i];
>> > +		/* maybe the user disabled all other modes: */
>> > +		if (new_mode =3D=3D mode)
>> > +			return mode;
>> > +	}
>> > +	return new_mode;
>> >  }
>
> Not a busy loop, since new_mode will reset at HOME_MODE (0)
> and then it'll hit "new_mode =3D=3D mode" and remain locked in
> to the current mode.

Right.  I see it now.  Thanks for explaining.

I guess I was expecting a complete loop bypass ala

  if (!max_mode)
     return mode:

but your solution will of course work just as fine.


Bj=C3=B8rn