From: Andrew Morton <akpm@linux-foundation.org>
To: Johan Hovold <jhovold@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>, Rob Landley <rob@landley.net>,
Samuel Ortiz <sameo@linux.intel.com>,
Jonathan Cameron <jic23@cam.ac.uk>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Florian Tobias Schandinat <FlorianSchandinat@gmx.de>,
Arnd Bergmann <arnd@arndb.de>,
Mark Brown <broonie@opensource.wolfsonmicro.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
Bryan Wu <bryan.wu@canonical.com>
Subject: Re: [PATCH v3] leds: add LM3533 LED driver
Date: Fri, 11 May 2012 15:24:36 -0700 [thread overview]
Message-ID: <20120511152436.5272ff1f.akpm@linux-foundation.org> (raw)
In-Reply-To: <20120511095411.GC29437@localhost>
On Fri, 11 May 2012 11:54:11 +0200
Johan Hovold <jhovold@gmail.com> wrote:
> On Thu, May 10, 2012 at 11:48:17AM -0700, Andrew Morton wrote:
> > On Thu, 10 May 2012 20:27:05 +0200
> > Johan Hovold <jhovold@gmail.com> wrote:
> >
> > > Add sub-driver for the LEDs on National Semiconductor / TI LM3533
> > > lighting power chips.
> > >
> > > The chip provides 256 brightness levels, hardware accelerated blinking
> > > as well as ambient-light-sensor and pwm input control.
> > >
> > > ...
> > >
> > > +#define to_lm3533_led(_cdev) \
> > > + container_of(_cdev, struct lm3533_led, cdev)
> >
> > Minor thing: container_of() is not fully type-safe: it can be passed
> > the address of any struct which contains a field called cdev and will
> > return a struct lm3533_led* (or something like that - it has holes...).
> >
> > A way to fix that is to wrap container_of() in a real C function, not a
> > macro:
> >
> > static inline struct lm3533_led *to_lm3533_led(struct struct led_classdev *cdev)
> > {
> > return container_of(_cdev, struct lm3533_led, cdev);
> > }
> >
> > This has been another episode in the ongoing series "macros are always
> > wrong" :)
>
> Fair enough. :) Seems like the vast majority of drivers still use
> convenience macros such as the this one for this kind of use (where the
> functions are either passed the class device or it is retrieved through
> device driver data).
>
> Do you want me to replace the other three instances of container_of
> convenience macros in the iio-subdriver and core (already added to the
> mfd tree) as well?
Well, it does result in better code. How could I say no? ;)
> > > +static ssize_t store_als(struct device *dev,
> > > + struct device_attribute *attr,
> > > + const char *buf, size_t len)
> > > +{
> > > + struct led_classdev *led_cdev = dev_get_drvdata(dev);
> > > + struct lm3533_led *led = to_lm3533_led(led_cdev);
> > > + u8 als;
> > > + u8 reg;
> > > + u8 mask;
> > > + int ret;
> > > +
> > > + if (kstrtou8(buf, 0, &als))
> > > + return -EINVAL;
> > > +
> > > + if (als != 0 && (als < LM3533_ALS_LV_MIN || als > LM3533_ALS_LV_MAX))
> > > + return -EINVAL;
> >
> > The `als != 0' test doesn't do anything, and looks odd. Is there some
> > magical reason why als==0 would be illegal even if LM3533_ALS_LV_MIN
> > was negative? If so, it should be documented.
>
> The non-zero-test is not redundant as 0 is the only valid input outside
> of [LV_MIN,LV_MAX] (in fact, the only three valid values are 0,2 and 3).
ah, OK. One day I'll get the hang of this C thingy.
> Would you prefer
>
> if ((als < LM3533_ALS_LV_MIN && als != 0) || als > LM3533_ALS_LV_MAX)
> return -EINVAL;
>
> or nested conditionals? Or should I simply add a comment?
A comment would be nice. That 0 is also permitted is a surprise.
next prev parent reply other threads:[~2012-05-11 22:24 UTC|newest]
Thread overview: 83+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-20 15:30 [PATCH 0/4] mfd: add LM3533 lighting-power chip driver Johan Hovold
2012-04-20 15:30 ` [PATCH 1/4] mfd: add LM3533 lighting-power core driver Johan Hovold
2012-04-26 12:41 ` Mark Brown
2012-05-03 10:15 ` Johan Hovold
2012-05-03 10:22 ` Johan Hovold
2012-04-20 15:30 ` [PATCH 2/4] misc: add LM3533 ambient light sensor driver Johan Hovold
2012-04-20 15:57 ` Greg Kroah-Hartman
2012-04-20 17:28 ` Johan Hovold
2012-04-20 17:37 ` Greg Kroah-Hartman
2012-04-26 11:52 ` Johan Hovold
2012-04-20 15:30 ` [PATCH 3/4] leds: add LM3533 LED driver Johan Hovold
2012-04-20 16:10 ` Arnd Bergmann
2012-04-20 16:45 ` Johan Hovold
2012-04-20 15:30 ` [PATCH 4/4] backlight: add LM3533 backlight driver Johan Hovold
2012-05-03 10:26 ` [PATCH v2 0/4] mfd: add LM3533 lighting-power chip driver Johan Hovold
2012-05-03 10:26 ` [PATCH v2 1/4] mfd: add LM3533 lighting-power core driver Johan Hovold
2012-05-03 10:38 ` Mark Brown
2012-05-03 11:28 ` Johan Hovold
2012-05-03 11:38 ` Mark Brown
2012-05-03 15:00 ` Johan Hovold
2012-05-03 15:24 ` Mark Brown
2012-05-03 16:54 ` Johan Hovold
2012-05-03 16:57 ` Mark Brown
2012-05-03 17:14 ` Johan Hovold
2012-05-03 17:23 ` Mark Brown
2012-05-03 17:31 ` Johan Hovold
2012-05-09 14:42 ` Samuel Ortiz
2012-05-10 12:07 ` Johan Hovold
2012-05-10 12:11 ` [PATCH 1/2] mfd: lm3533: add boost frequency and ovp to platform data Johan Hovold
2012-05-10 12:11 ` [PATCH 2/2] mfd: lm3533: remove boost attributes Johan Hovold
2012-05-10 17:18 ` [PATCH 0/2] mfd: lm3533: update max-current interface Johan Hovold
2012-05-10 17:18 ` [PATCH 1/2] mfd: lm3533: remove unused max-current function Johan Hovold
2012-05-10 17:18 ` [PATCH 2/2] mfd: lm3533: use SI-units for max-current interface Johan Hovold
2012-05-11 13:32 ` [PATCH v2 1/4] mfd: add LM3533 lighting-power core driver Samuel Ortiz
2012-05-03 10:26 ` [PATCH v2 2/4] iio: add LM3533 ambient light sensor driver Johan Hovold
2012-05-03 11:40 ` Jonathan Cameron
2012-05-03 16:36 ` Johan Hovold
2012-05-08 13:47 ` Jonathan Cameron
2012-05-15 16:44 ` Johan Hovold
2012-05-15 20:00 ` Jonathan Cameron
2012-05-16 13:05 ` Johan Hovold
2012-05-16 14:21 ` Jonathan Cameron
2012-05-18 12:27 ` Johan Hovold
2012-05-18 17:34 ` Jonathan Cameron
2012-05-18 17:57 ` Johan Hovold
2012-05-19 8:04 ` Jonathan Cameron
2012-05-15 16:46 ` [PATCH v3] iio: add LM3533 ambient-light-sensor driver Johan Hovold
2012-05-15 19:27 ` Andrew Morton
2012-05-15 20:00 ` Johan Hovold
2012-05-15 20:16 ` Jonathan Cameron
2012-05-18 13:07 ` [PATCH v4] " Johan Hovold
2012-05-19 8:48 ` Jonathan Cameron
2012-05-19 16:30 ` Johan Hovold
2012-05-19 13:26 ` Jonathan Cameron
2012-05-21 9:50 ` Johan Hovold
2012-05-21 16:37 ` Jonathan Cameron
2012-05-21 22:07 ` Johan Hovold
2012-05-22 7:13 ` Jonathan Cameron
2012-05-22 9:09 ` Johan Hovold
2012-05-22 9:15 ` Jonathan Cameron
2012-05-22 7:45 ` Michael Hennerich
2012-05-22 7:49 ` Jonathan Cameron
2012-05-22 8:11 ` Michael Hennerich
2012-05-22 8:20 ` Jonathan Cameron
2012-05-21 12:18 ` [PATCH v5] " Johan Hovold
2012-05-22 9:19 ` Jonathan Cameron
2012-05-22 9:40 ` Johan Hovold
2012-05-22 13:55 ` Greg Kroah-Hartman
2012-06-05 4:11 ` Greg Kroah-Hartman
2012-05-03 10:26 ` [PATCH v2 3/4] leds: add LM3533 LED driver Johan Hovold
2012-05-03 10:43 ` Mark Brown
2012-05-03 11:50 ` Johan Hovold
2012-05-03 14:51 ` Mark Brown
2012-05-03 16:46 ` Johan Hovold
2012-05-10 18:27 ` [PATCH v3] " Johan Hovold
2012-05-10 18:48 ` Andrew Morton
2012-05-11 9:54 ` Johan Hovold
2012-05-11 22:24 ` Andrew Morton [this message]
2012-05-14 10:25 ` Johan Hovold
2012-05-14 10:31 ` [PATCH v4] " Johan Hovold
2012-05-03 10:26 ` [PATCH v2 4/4] backlight: add LM3533 backlight driver Johan Hovold
2012-05-10 18:29 ` [PATCH v3] " Johan Hovold
2012-05-15 19:13 ` [PATCH v4] " Johan Hovold
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