linux-kernel - Re: [PATCH v2 0/3] leds: blink resolution improvements

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20150503103436.GA4317@amd>
Date:	Sun, 3 May 2015 12:34:36 +0200
From:	Pavel Machek <pavel@....cz>
To:	Stas Sergeev <stsp@...t.ru>
Cc:	linux-leds@...r.kernel.org,
	Linux kernel <linux-kernel@...r.kernel.org>,
	Stas Sergeev <stsp@...rs.sourceforge.net>
Subject: Re: [PATCH v2 0/3] leds: blink resolution improvements


> >What about simply "echo 0.001 > delay_on"?
> This is possible.
> But please consider the following reservations:
> - There is already 2 files, so you are not going to write settings
> atomically anyway. When resolution changes, it might be better
> to just reset to the sane defaults (not in my current patch).

Sane defaults would be mandatory, but lets get reasonable interface.

Someone left 1 in delay_on. You want 100 nsec. You echo nsec >
delay_on_units, bang, dead machine, looping in kernel.

Someone left 100 / nsec in delay on. You want one usec. Echo 1 >
delay_on, bang, dead machine.

> - As was already discussed in the same thread, not all drivers
> can support sub-ms delays. For these drivers such resolutions
> should not be available. With separate file this is naturally
> achieved: you either don't create it at all, or list only the possible
> resolutions. With your approach you never know whether you
> can write 0.0001 or not.

Well, so you get back einval. Knowing "unit" is not enough to know how
short delays hw can support.

> - You will set the delay in ms units. For example for 100us you'll
> write 0.1. IMHO it is counter-intuitive: people will make a mistake
> and try 0.0001 instead, wrongly assuming that this is in seconds.
> And nanoseconds should then better be removed, as writing
> nanosecond delay will just require too much zeros.

This is machine-to-machine interface. And users can handle this.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/