linux-kernel - Re: [PATCH] isl29020: ambient light sensor

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] [day] [month] [year] [list]

Message-ID: <20101022210132.72389768@lxorguk.ukuu.org.uk>
Date:	Fri, 22 Oct 2010 21:01:32 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] isl29020: ambient light sensor

On Fri, 22 Oct 2010 12:51:30 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Fri, 22 Oct 2010 13:46:07 +0100
> Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> 
> > From: Kalhan Trisal <kalhan.trisal@...el.com>
> > 
> > The LS driver will read the latest Lux measurement based upon the
> > light brightness and will report the LUX output through sysfs interface.
> > 
> > This hardware isn't quite the same as the ISL29003 so has a different driver.
> > 
> >
> > ...
> >
> > +static ssize_t als_lux_input_data_show(struct device *dev,
> > +			struct device_attribute *attr, char *buf)
> > +{
> > +	struct i2c_client *client = to_i2c_client(dev);
> > +	int ret_val, val;
> > +	unsigned long int lux;
> > +	int temp;
> > +
> > +	pm_runtime_get_sync(dev);
> > +	msleep(100);
> 
> The msleep() is a bit mysterious.  And long!  A little code comment
> explaining why it's here would illuminate things (heh, I kill me).

It takes that long to get a sensible answer from the device after you
power it up and sysfs doesn't keep enough context around to do poll etc.

It may be possible to shorten it if we've not been suspended but there
isn't a sane way I've found to track last suspended time nicely and race
free in the runtime_pm layer.

> Could/should we make the PM code disappear if !CONFIG_PM?  Such as

Looks sensible. Will add to it.

Alan
--
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/