Re: [PATCH] USB: Only enable autosuspend by default on certain device classes

On 8/3/07, Rogan Dawes <[email protected]> wrote:
> Matthew Garrett wrote:
> > On Fri, Aug 03, 2007 at 01:44:02PM +0200, Oliver Neukum wrote:
> >> Am Freitag 03 August 2007 schrieb Matthew Garrett:
> >>> It's certainly possible to do that, but it's also possible to have a
> >>> userspace solution that whitelists devices. The question is whether the
> >>> default kernel behaviour should be "Save power, but potentially break
> >>> some of my devices" or "Don't break my devices, but use some more
> >>> powre".
> >> If both options have drawbacks, IMHO we follow the standard, which
> >> says that devices must support suspension.
> >
> > Except that lots of hardware doesn't follow the standard in this
> > respect, otherwise we wouldn't be having this discussion. Personally, I
> > think "Will break an unknown number of devices" is a significantly
> > larger drawback than "Will consume a small quantity of additional
> > power".
> >
>
> I guess the question could be phrased:
>
> Which one is more likely to conclude at some point?
>
> That is, if we blacklist by default, we consume that additional power
> indefinitely, because it is unlikely that people will report "my machine
> uses 200mW more than I think it should", and thus we are unlikely to
> build up knowledge of exactly which devices/classes should be blacklisted.
>
> Compare that to:
>
> "My USB printer broke, guess I'd better report it to LKML".
>
> The first option is unlikely to ever reach a satisfactory conclusion,
> whereas the second one is quite likely to flush out the guilty parties
> within a relatively short time.

Even though we should be following what the specs says and find other
ways of threating the "messy" devices. A sysfs entry for
enabling/disabling autosuspend and even to add devices to blacklist
seems quite nice to me.

>
> FWIW.
>
> Rogan
>
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-- 
Best Regards,

Felipe Balbi
[email protected]

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