linux-kernel - Re: [PATCH 7/7] staging:iio:dac: Add AD5380 driver

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Date:	Fri, 18 Nov 2011 10:08:40 +0100
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Jonathan Cameron <jic23@...nel.org>
CC:	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>,
	Michael Hennerich <michael.hennerich@...log.com>,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
	device-drivers-devel@...ckfin.uclinux.org, drivers@...log.com
Subject: Re: [PATCH 7/7] staging:iio:dac: Add AD5380 driver

On 11/17/2011 09:24 PM, Jonathan Cameron wrote:
> On 11/16/2011 03:28 PM, Lars-Peter Clausen wrote:
>> This patch adds support for the Analog Devices D5380, AD5381,
>> AD5382, AD5383, AD5384, AD5390, AD5391, AD5392 multi-channel
>> Digital to Analog Converters.
>>
>> Signed-off-by: Lars-Peter Clausen <lars@...afoo.de>
>>
>> ---
>> There should be no compile time dependencies to the regmap patches earlier in
>> this series, so this patch can be merged independently of it.
> Should probably have been a separate series!  Doesn't matter for review
> though and I guess you justified some of the other patches with it.
>> ---
>>  drivers/staging/iio/dac/Kconfig  |   11 +
>>  drivers/staging/iio/dac/Makefile |    1 +
>>  drivers/staging/iio/dac/ad5380.c |  669 ++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 681 insertions(+), 0 deletions(-)
>>  create mode 100644 drivers/staging/iio/dac/ad5380.c
>>[...]
>> +
>> +static ssize_t ad5380_write_powerdown_mode(struct device *dev,
>> +	struct device_attribute *attr, const char *buf, size_t len)
>> +{
>> +	struct iio_dev *indio_dev = dev_get_drvdata(dev);
>> +	struct ad5380_state *st = iio_priv(indio_dev);
>> +	unsigned int i;
>> +	int ret;
>> +
> Excess brackets for that for loop I think

I prefer to have them since the loop contains a multiple lines.

>> +	for (i = 0; i < ARRAY_SIZE(ad5380_powerdown_modes); ++i) {
>> +		if (sysfs_streq(buf, ad5380_powerdown_modes[i]))
>> +			break;
>> +	}
>> +
>> +	if (i == ARRAY_SIZE(ad5380_powerdown_modes))
>> +		return -EINVAL;
>> +
>> +	ret = regmap_update_bits(st->regmap, AD5380_REG_SF_CTRL,
>> +		1 << AD5380_CTRL_PWR_DOWN_MODE_OFFSET,
>> +		i << AD5380_CTRL_PWR_DOWN_MODE_OFFSET);
> Obviously both of these will be cleaner with it as a bit.

When writing this using BIT it would be i ? AD5380_CTRL_PWR_DOWN_MODE_BIT :
0... And also this is about semantics. The other bits are bits in the sense
of true/false. While this is an enumeration which just happens to have only
one bit. But I can change it, if you prefer using BIT here.

>> +
>> +	return ret ? ret : len;
>> +}
>> +
> Not a comment on this driver, but we need to have a think about
> whether these will ever want to be controlled via in kernel
> interfaces and if so how the heck we are going to do it!

Yes, definitely. But I think it is best to discuss this in a separate thread.

>> +static IIO_DEVICE_ATTR(out_voltage_powerdown_mode,
>> +			S_IRUGO | S_IWUSR,
>> +			ad5380_read_powerdown_mode,
>> +			ad5380_write_powerdown_mode, 0);
>> +
>> +static IIO_CONST_ATTR(out_voltage_powerdown_mode_available,
>> +			"100kohm_to_gnd three_state");
>> +
>> +static struct attribute *ad5380_attributes[] = {
>> +	&iio_dev_attr_out_voltage_powerdown.dev_attr.attr,
>> +	&iio_dev_attr_out_voltage_powerdown_mode.dev_attr.attr,
>> +	&iio_const_attr_out_voltage_powerdown_mode_available.dev_attr.attr,
>> +	NULL,
>> +};
> [...]
>> +static const struct i2c_device_id ad5380_i2c_ids[] = {
>> +	{ "ad5380-3", ID_AD5380_3 },
>> +	{ "ad5380-5", ID_AD5380_5 },
>> +	{ "ad5381-3", ID_AD5381_3 },
>> +	{ "ad5381-5", ID_AD5381_5 },
>> +	{ "ad5382-3", ID_AD5382_3 },
>> +	{ "ad5382-5", ID_AD5382_5 },
>> +	{ "ad5383-3", ID_AD5383_3 },
>> +	{ "ad5383-5", ID_AD5383_5 },
>> +	{ "ad5390-3", ID_AD5380_3 },
>> +	{ "ad5390-5", ID_AD5380_5 },
>> +	{ "ad5391-3", ID_AD5381_3 },
>> +	{ "ad5391-5", ID_AD5381_5 },
>> +	{ "ad5392-3", ID_AD5382_3 },
>> +	{ "ad5392-5", ID_AD5382_5 },
> I'm guessing you defined the ID_AD5392 etc for a reason?

Ooops, yes. Good catch.

Thanks for the review.
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