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    SubjectRe: [PATCH V6 1/2] introduce ALS sysfs class
    On Thu 2009-09-03 02:16:04, Rafael J. Wysocki wrote:
    > On Wednesday 02 September 2009, Pavel Machek wrote:
    > > 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.
    >
    > The interface is already defined, isn't it? And we're now
    > considering whether

    No, I don't think it is "already defined". Yes the patches float
    around, but as nothing is merged we can still fix it easily.
    Pavel

    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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