linux-kernel - Re: lm90 driver no longer working on PCs in 3.13

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Date:	Mon, 27 Jan 2014 11:10:41 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	Jean Delvare <khali@...ux-fr.org>,
	Guenter Roeck <linux@...ck-us.net>,
	LM Sensors <lm-sensors@...sensors.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Liam Girdwood <lgirdwood@...il.com>, Wei Ni <wni@...dia.com>
Subject: Re: lm90 driver no longer working on PCs in 3.13

On Mon, Jan 27, 2014 at 12:15 AM, Mark Brown <broonie@...nel.org> wrote:
>> No, you don't get what I'm saying. For PC users, the lm90 did not
>
> I understand perfectly well thank you very much.
>
>> request a regulator and things worked because the kernel isn't supposed
>> to take care about things like that on PC machines. Now that the lm90
>> driver does request a regulator, it fails on PC machines because no
>> regulator is declared.
>
> If and only if the user has enabled the regulator API on a platform that
> hasn't fully configured it; if the user has not enabled the regulator
> API it'll stub itself out and they'll never see it.
>
>> Don't tell me that it is expected that things will fail if
>> CONFIG_REGULATOR is enabled on a system which doesn't need it. It
>> doesn't make any sense. If kernels would fail as soon as any enabled
>> option wasn't actually needed, no system would boot out there.
>
> It's very easy to generate unbootable kernels by changing the kernel
> config, I'd not immediately expect a randomly generated config to do
> anything useful and things like FW_LOADER_USER_HELPER can be rather
> miserable if you turn them on (that one produces enormous delays during
> init which look awfully like hangs when you're watching your board
> boot).

This is not just a randomly generated config where you disable critical
options. Just enabling a subsystem like the regulator subsystem shouldn't
give you an unbootable kernel. It's even needed, think multi-platform
kernels.
Typically, I'd expect allmodconfig/allyesconfig kernels to actually boot
(ignoring RAM size issues etc.).

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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