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Message-Id: <20120510114817.28b24168.akpm@linux-foundation.org>
Date: Thu, 10 May 2012 11:48:17 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Johan Hovold <jhovold@...il.com>
Cc: Richard Purdie <rpurdie@...ys.net>, Rob Landley <rob@...dley.net>,
Samuel Ortiz <sameo@...ux.intel.com>,
Jonathan Cameron <jic23@....ac.uk>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Florian Tobias Schandinat <FlorianSchandinat@....de>,
Arnd Bergmann <arnd@...db.de>,
Mark Brown <broonie@...nsource.wolfsonmicro.com>,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
Bryan Wu <bryan.wu@...onical.com>
Subject: Re: [PATCH v3] leds: add LM3533 LED driver
On Thu, 10 May 2012 20:27:05 +0200
Johan Hovold <jhovold@...il.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" :)
>
> ...
>
> +static int time_to_val(long *t, long t_min, long t_max, long t_step,
> + int v_min, int v_max)
> +{
> + int val;
> +
> + *t += t_step / 2;
> + val = (*t - t_min) / t_step + v_min;
> + val = clamp(val, v_min, v_max);
> + *t = t_step * (val - v_min) + t_min;
> +
> + return val;
> +}
Oh wow, what does all this do. Please, take pity upon the poor reader
and add a comment documenting this function's intent?
> +static int lm3533_led_get_delay(long *delay)
> +{
> + int val;
> +
> + *delay *= 1000;
> +
> + if (*delay >= LM3533_LED_DELAY_GROUP3_MIN -
> + LM3533_LED_DELAY_GROUP3_STEP / 2) {
> + val = time_to_val(delay, LM3533_LED_DELAY_GROUP3_MIN,
> + LM3533_LED_DELAY_GROUP3_MAX,
> + LM3533_LED_DELAY_GROUP3_STEP,
> + LM3533_LED_DELAY_GROUP3_BASE,
> + 0xff);
> + } else if (*delay >= LM3533_LED_DELAY_GROUP2_MIN -
> + LM3533_LED_DELAY_GROUP2_STEP / 2) {
> + val = time_to_val(delay, LM3533_LED_DELAY_GROUP2_MIN,
> + LM3533_LED_DELAY_GROUP2_MAX,
> + LM3533_LED_DELAY_GROUP2_STEP,
> + LM3533_LED_DELAY_GROUP2_BASE,
> + LM3533_LED_DELAY_GROUP3_BASE - 1);
> + } else {
> + val = time_to_val(delay, LM3533_LED_DELAY_GROUP1_MIN,
> + LM3533_LED_DELAY_GROUP1_MAX,
> + LM3533_LED_DELAY_GROUP1_STEP,
> + LM3533_LED_DELAY_GROUP1_BASE,
> + LM3533_LED_DELAY_GROUP2_BASE - 1);
> + }
> +
> + *delay /= 1000;
> +
> + return val;
> +}
And this one, please.
> +static int lm3533_led_delay_set(struct lm3533_led *led, u8 base,
> + unsigned long *delay)
> +{
> + u8 val;
> + u8 reg;
> + long t;
> + int ret;
> +
> + t = *delay;
> + val = lm3533_led_get_delay(&t);
> +
> + dev_dbg(led->cdev.dev, "%s - %lu: %ld (0x%02x)\n", __func__,
> + *delay, t, val);
> + reg = lm3533_led_get_pattern_reg(led, base);
> + ret = lm3533_write(led->lm3533, reg, val);
> + if (ret)
> + dev_err(led->cdev.dev, "failed to set delay (%02x)\n", reg);
> +
> + *delay = t;
> +
> + return ret;
> +}
Should `t' have unsigned long type? I think so. The above functions
confuddle longs with unsigned longs. As a negative delay is an
absurdity, perhaps everything should use unsigned long consistently?
> +static int lm3533_led_delay_on_set(struct lm3533_led *led, unsigned long *t)
> +{
> + *t = min_t(long, *t, LM3533_LED_DELAY_GROUP2_MAX / 1000);
The use of min_t is often a sign that the types are mucked up. How to
fix this?
Are the LM3533_LED_DELAY_* constants logically to be considered to have
unsigned long type? If so, put a "L" after their values and everything
should work out nicely.
> + return lm3533_led_delay_set(led, LM3533_REG_PATTERN_HIGH_TIME_BASE, t);
> +}
> +
>
> ...
>
> +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.
> +
> + reg = lm3533_led_get_lv_reg(led, LM3533_REG_CTRLBANK_BCONF_BASE);
> + mask = LM3533_REG_CTRLBANK_BCONF_ALS_MASK;
> +
> + ret = lm3533_update(led->lm3533, reg, als, mask);
> + if (ret)
> + return ret;
> +
> + return len;
> +}
> +
>
> ...
>
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