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Date: Wed, 01 May 2013 16:07:17 +0200
From: Lars-Peter Clausen <lars@...afoo.de>
To: Oskar Andero <oskar.andero@...il.com>
CC: linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
Jonathan Cameron <jic23@....ac.uk>
Subject: Re: [PATCH] iio: adc: add driver for MCP3204/08 12-bit ADC
On 05/01/2013 12:21 AM, Oskar Andero wrote:
> This adds support for Microchip's 12 bit AD converters MCP3204 and
> MCP3208. These chips communicates over SPI and supports single-ended
> and pseudo-differential configurations.
>
> Cc: Jonathan Cameron <jic23@....ac.uk>
> Cc: Lars-Peter Clausen <lars@...afoo.de>
> Signed-off-by: Oskar Andero <oskar.andero@...il.com>
Hi,
Looks very good in general. A few minor things, mostly related to the regulator
handling and a couple of nitpicks inline.
> ---
> drivers/iio/adc/Kconfig | 10 ++
> drivers/iio/adc/Makefile | 1 +
> drivers/iio/adc/mcp320x.c | 261 ++++++++++++++++++++++++++++++++++
> include/linux/platform_data/mcp320x.h | 23 +++
> 4 files changed, 295 insertions(+)
> create mode 100644 drivers/iio/adc/mcp320x.c
> create mode 100644 include/linux/platform_data/mcp320x.h
>
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index ab0767e6..93129ec 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
[...]
> +
> +static int mcp320x_read_raw(struct iio_dev *iio,
> + struct iio_chan_spec const *channel, int *val,
> + int *val2, long mask)
> +{
> + struct mcp320x *adc = iio_priv(iio);
> + int ret = -EINVAL;
> +
> + mutex_lock(&adc->lock);
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
[...]
> + case IIO_CHAN_INFO_SCALE:
> + /* Digital output code = (4096 * Vin) / Vref */
> + if (!IS_ERR_OR_NULL(adc->reg)) {
> + ret = regulator_get_voltage(adc->reg);
> + if (ret < 0)
> + goto out;
> + *val = ret / 1000;
> + } else {
> + *val = adc->ref_mv;
> + }
> + *val2 = 4096 * 1000;
The scale of voltage channels is in mV. So I think the * 1000 should be removed.
> + ret = IIO_VAL_FRACTIONAL;
> + break;
> +
> + default:
> + break;
> + }
> +
> +out:
> + mutex_unlock(&adc->lock);
> +
> + return ret;
> +}
[...]h
> +static int mcp320x_probe(struct spi_device *spi)
> +{
> + struct mcp320x_platform_data *pdata = spi->dev.platform_data;
> + struct iio_dev *iio;
It's not a big deal, but usually we call the iio_dev variabl indio_dev would be
nice for consistency to use this name in your driver as well.
> + struct mcp320x *adc;
> + int ret;
> +
> + if (!pdata) {
> + dev_err(&spi->dev, "No platform data!");
> + return -EINVAL;
> + }
> +
> + iio = iio_device_alloc(sizeof(*adc));
> + if (!iio)
> + return -ENOMEM;
> +
> + adc = iio_priv(iio);
> + adc->spi = spi;
> +
> + iio->dev.parent = &spi->dev;
> + iio->name = spi_get_device_id(spi)->name;
> + iio->modes = INDIO_DIRECT_MODE;
> + iio->info = &mcp320x_info;
> +
> + if (spi_get_device_id(spi)->driver_data == mcp3204) {
> + iio->channels = mcp3204_channels;
> + iio->num_channels = ARRAY_SIZE(mcp3204_channels);
> + } else {
> + iio->channels = mcp3208_channels;
> + iio->num_channels = ARRAY_SIZE(mcp3208_channels);
> + }
Usually we use a lookup table for this. E.g
struct mcp3208_chip_info {
struct iio_chan_spec *channels;
unsigned int num_channels;
};
static const struct mcp3208_chip_info[] = {
[mcp3204] = {
.channels = mcp3204_channels,
.num_channels = ARRAY_SIZE(mcp3204_channels)
},
[mcp3204] = {
...
},
};
indio_dev->channels = mcp3208_chip_info[id].channels;
indio_dev->num_channels = mcp3208_chip_info[id].num_channels;
This keeps things a bit more tidy. Especially if more chip variants are added
later.
> +
> + adc->transfer[0].tx_buf = &adc->tx_buf;
> + adc->transfer[0].len = sizeof(adc->tx_buf);
> + adc->transfer[1].rx_buf = adc->rx_buf;
> + adc->transfer[1].len = sizeof(adc->rx_buf);
> +
> + spi_message_init(&adc->msg);
> + spi_message_add_tail(&adc->transfer[0], &adc->msg);
> + spi_message_add_tail(&adc->transfer[1], &adc->msg);
There is a new helper function which makes this a bit shorter:
spi_message_init_with_transfers(&adc->msg, adc->transfer,
ARRAY_SIZE(adc->transfer));
> +
> + if (pdata->reg) {
> + adc->reg = regulator_get(&spi->dev, pdata->reg);
This not how the regulator API is supposed to be used. The regulator name
should be const. E.g. "vref". Your board code then provides a lookup table map
the regulator to the name in the consumer.
> + if (IS_ERR_OR_NULL(adc->reg))
> + return PTR_ERR(adc->reg);
So what happens in the OR_NULL case? I think it is save to just use
IS_ERR(adc->reg)
> +
> + ret = regulator_enable(adc->reg);
> + if (ret < 0)
> + goto reg_free;
> + } else {
> + adc->ref_mv = pdata->ref_mv;
I'd like to see this fallback path go away. For supplies with a const voltage
the fixed-voltage-regulator can be used.
> + }
> +
> + mutex_init(&adc->lock);
> +
> + ret = iio_device_register(iio);
> + if (ret < 0)
> + goto iio_free;
> +
> + return 0;
> +
> +iio_free:
> + iio_device_free(iio);
> +reg_free:
> + if (!IS_ERR_OR_NULL(adc->reg))
> + regulator_put(adc->reg);
> +
> + return ret;
> +}
> +
> +static int mcp320x_remove(struct spi_device *spi)
> +{
> + struct iio_dev *iio = spi_get_drvdata(spi);
> + struct mcp320x *adc = iio_priv(iio);
> +
> + if (!IS_ERR_OR_NULL(adc->reg)) {
> + regulator_disable(adc->reg);
> + regulator_put(adc->reg);
> + }
First unregister the device, then free the regulator, then free the device.
> +
> + iio_device_unregister(iio);
> + iio_device_free(iio);
> +
> + return 0;
> +}
[...]
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