linux-kernel - Re: [PATCH V6 1/2] introduce ALS sysfs class

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]

Date:	Wed, 2 Sep 2009 23:51:49 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Zhang Rui <rui.zhang@...el.com>, Len Brown <lenb@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-acpi <linux-acpi@...r.kernel.org>, Greg KH <greg@...ah.com>
Subject: Re: [PATCH V6 1/2] introduce ALS sysfs class

On Wed 2009-09-02 23:46:11, Rafael J. Wysocki wrote:
> On Wednesday 02 September 2009, Pavel Machek wrote:
> > On Wed 2009-09-02 23:12:58, Rafael J. Wysocki wrote:
> > > On Tuesday 01 September 2009, Pavel Machek wrote:
> > > > 
> > > > > > > IMO, 0 and -1 are not errors. they just suggest that the Ambient Light
> > > > > > > illuminance is beyond the device support range, while the device is
> > > > > > > still working normally.
> > > > > > > what about exporting these values (0 and -1) to user space directly?
> > > > > > 
> > > > > > Returning 0 for "below" range and 99999999 for "above" range would be
> > > > > > nice, yes. 
> > > > > 
> > > > > Why not 0 and "all ones" or 0 and -1.
> > > > > 
> > > > > Is there anything wrong with -1 in particular?
> > > > 
> > > > Normal people expect -1 to be less than 123, and output is in ascii. If
> > > > you make it ((unsigned) ~0) I guess that becomes acceptable.
> > > 
> > > Well, "-1" is a perfectly valid alphanumerical representation of an int.
> > > I don't really see the problem with the "-", unless we're talking about some
> > > broken user space, that is.
> > 
> > No. But if you see illumination value of -1 lumen, do you really
> > expect a *lot* of light?
> 
> Not really.  I'd rather intrepret it as "the number is not to be trusted",
> which is what it means.
> 
> The problem with "all ones" is that it depends on the size of the underlying
> data type, which is not nice.  Also, if you want that to be a "big number",
> there's no clear rule to tell what the number should actually be.
> 
> Anyway, this really is a matter of definition.  If we document the attribute
> to read as "-1" in specific circumstances, the user space will have to take
> that into account.

Well, I'd prefer to specify -1 as "underflow" and 1000000000 as
"overflow". Any numbers should work, but ... lets make the interface
logical if we can.

									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/