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Date: Thu, 16 Jul 2020 11:25:36 +0200
From: Lars-Peter Clausen <lars@...afoo.de>
To: Cristian Pop <cristian.pop@...log.com>, linux-iio@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: jic23@...nel.org
Subject: Re: [RFC PATCH] one-bit-adc-dac: Add initial version of one bit ADC,
DAC
On 7/16/20 9:27 AM, Cristian Pop wrote:
> Implementation for 1-bit ADC (comparator) and a 1-bit DAC (switch)
Very sneaky way of introducing a iio-gpio-proxy driver to be able to
access GPIOs through libiio ;). I'm not really a fan of the whole idea.
But either way I think this needs a better description of what 1-bit
converters are and how they are used.
>
> Signed-off-by: Cristian Pop <cristian.pop@...log.com>
> ---
> drivers/iio/addac/one-bit-adc-dac.c | 229 ++++++++++++++++++++++++++++
> 1 file changed, 229 insertions(+)
> create mode 100644 drivers/iio/addac/one-bit-adc-dac.c
>
> diff --git a/drivers/iio/addac/one-bit-adc-dac.c b/drivers/iio/addac/one-bit-adc-dac.c
> new file mode 100644
> index 000000000000..8e2a8a09fedb
> --- /dev/null
> +++ b/drivers/iio/addac/one-bit-adc-dac.c
> @@ -0,0 +1,229 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Analog Devices ONE_BIT_ADC_DAC
> + * Digital to Analog Converters driver
> + *
> + * Copyright 2019 Analog Devices Inc.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/iio/iio.h>
> +#include <linux/platform_device.h>
> +#include <linux/gpio/consumer.h>
> +
> +enum ch_direction {
> + CH_IN,
> + CH_OUT,
> +};
> +
> +struct one_bit_adc_dac_state {
> + struct platform_device *pdev;
> + struct gpio_descs *in_gpio_descs;
> + struct gpio_descs *out_gpio_descs;
> +};
> +
> + #define ONE_BIT_ADC_DAC_CHANNEL(idx, direction) \
> + { \
> + .type = IIO_VOLTAGE, \
> + .indexed = 1, \
> + .channel = idx, \
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> + .output = direction, \
> + }
> +
> +static int one_bit_adc_dac_read_raw(struct iio_dev *indio_dev,
> + const struct iio_chan_spec *chan, int *val, int *val2, long info)
> +{
> + struct one_bit_adc_dac_state *st = iio_priv(indio_dev);
> + int in_num_ch = 0, out_num_ch = 0;
> + int channel = chan->channel;
> +
> + if (st->in_gpio_descs)
> + in_num_ch = st->in_gpio_descs->ndescs;
> +
> + if (st->out_gpio_descs)
> + out_num_ch = st->out_gpio_descs->ndescs;
> +
> + switch (info) {
> + case IIO_CHAN_INFO_RAW:
> + if (channel < in_num_ch) {
> + *val = gpiod_get_value_cansleep(
> + st->in_gpio_descs->desc[channel]);
> + } else {
> + channel -= in_num_ch;
> + *val = gpiod_get_value_cansleep(
> + st->out_gpio_descs->desc[channel]);
> + }
> + return IIO_VAL_INT;
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static int one_bit_adc_dac_write_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int val,
> + int val2,
> + long info)
> +{
> + struct one_bit_adc_dac_state *st = iio_priv(indio_dev);
> + int in_num_ch = 0, out_num_ch = 0;
> + int channel = chan->channel;
> +
> + if (st->in_gpio_descs)
> + in_num_ch = st->in_gpio_descs->ndescs;
> +
> + if (st->out_gpio_descs)
> + out_num_ch = st->out_gpio_descs->ndescs;
> +
> + switch (info) {
> + case IIO_CHAN_INFO_RAW:
> + if (channel < in_num_ch) {
> + gpiod_set_value_cansleep(
> + st->in_gpio_descs->desc[channel], val);
How can we set a value on an input GPIO?
> + } else {
> + channel -= in_num_ch;
> + gpiod_set_value_cansleep(
> + st->out_gpio_descs->desc[channel], val);
> + }
> +
> + return 0;
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static const struct iio_info one_bit_adc_dac_info = {
> + .read_raw = &one_bit_adc_dac_read_raw,
> + .write_raw = &one_bit_adc_dac_write_raw,
> +};
> +
> +static int one_bit_adc_dac_set_ch(struct iio_dev *indio_dev,
> + struct iio_chan_spec *channels,
> + const char *propname,
> + int num_ch,
> + enum ch_direction direction,
> + int offset)
> +{
> + struct one_bit_adc_dac_state *st = iio_priv(indio_dev);
> + const char **gpio_names;
> + int ret, i;
> +
> + if (num_ch <= 0)
> + return 0;
> +
> + gpio_names = devm_kcalloc(indio_dev->dev.parent,
> + num_ch,
> + sizeof(char *),
sizeof(*gpio_names). It might be better to use normal kcalloc, kfree
here since you only use it in this function.
> + GFP_KERNEL);
> + if (!gpio_names)
> + return -ENOMEM;
> +
> + ret = device_property_read_string_array(&st->pdev->dev,
> + propname,
> + gpio_names,
> + num_ch);
> + if (ret < 0)
> + return ret;
> +
> + for (i = 0; i < num_ch; i++) {
> + channels[i] = (struct iio_chan_spec)ONE_BIT_ADC_DAC_CHANNEL(i +
> + offset,
> + direction);
> + channels[i].extend_name = gpio_names[i];
I think we want to avoid using extend_name in new drivers because it
makes for a very clumsy ABI. We should add a label property like we have
for the device for channels to have a symbolic name of the channel.
> + }
> +
> + return 0;
> +}
> +
> +static int one_bit_adc_dac_parse_dt(struct iio_dev *indio_dev)
> +{
> + struct one_bit_adc_dac_state *st = iio_priv(indio_dev);
> + struct iio_chan_spec *channels;
> + int ret, in_num_ch = 0, out_num_ch = 0;
> +
> + st->in_gpio_descs = devm_gpiod_get_array_optional(&st->pdev->dev,
> + "in", GPIOD_IN);
> + if (IS_ERR(st->in_gpio_descs))
> + return PTR_ERR(st->in_gpio_descs);
> +
> + if (st->in_gpio_descs)
> + in_num_ch = st->in_gpio_descs->ndescs;
> +
> + st->out_gpio_descs = devm_gpiod_get_array_optional(&st->pdev->dev,
> + "out", GPIOD_OUT_HIGH);
> + if (IS_ERR(st->out_gpio_descs))
> + return PTR_ERR(st->out_gpio_descs);
> +
> + if (st->out_gpio_descs)
> + out_num_ch = st->out_gpio_descs->ndescs;
> +
> + channels = devm_kcalloc(indio_dev->dev.parent, (in_num_ch + out_num_ch),
> + sizeof(struct iio_chan_spec), GFP_KERNEL);
sizeof(*channels) to avoid accidentally using the wrong type.
> + if (!channels)
> + return -ENOMEM;
> +
> + ret = one_bit_adc_dac_set_ch(indio_dev, &channels[0],
> + "in-gpio-names", in_num_ch,
> + CH_IN, 0);
> + if (ret < 0)
> + return ret;
> +
> + ret = one_bit_adc_dac_set_ch(indio_dev, &channels[in_num_ch],
> + "out-gpio-names", out_num_ch,
> + CH_OUT, in_num_ch);
> + if (ret < 0)
> + return ret;
> +
> + indio_dev->channels = channels;
> + indio_dev->num_channels = in_num_ch + out_num_ch;
> +
> + return 0;
> +}
> +
> +static int one_bit_adc_dac_probe(struct platform_device *pdev)
> +{
> + struct iio_dev *indio_dev;
> + struct one_bit_adc_dac_state *st;
> + int ret;
> +
> + indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*st));
> + if (!indio_dev)
> + return -ENOMEM;
> +
> + st = iio_priv(indio_dev);
> + st->pdev = pdev;
> + indio_dev->dev.parent = &pdev->dev;
parent assignment should not be needed thanks to Alex's work.
> + indio_dev->name = "one-bit-adc-dac";
> + indio_dev->modes = INDIO_DIRECT_MODE;
> + indio_dev->info = &one_bit_adc_dac_info;
> +
> + ret = one_bit_adc_dac_parse_dt(indio_dev);
> + if (ret < 0)
> + return ret;
> +
> + platform_set_drvdata(pdev, indio_dev);
There does not seem to be a matching get_drvdata() anywhere so this is
not needed.
> + return devm_iio_device_register(indio_dev->dev.parent, indio_dev);
> +}
> +
> +static const struct of_device_id one_bit_adc_dac_dt_match[] = {
> + { .compatible = "adi,one-bit-adc-dac" },
> + {},
> +};
> +
> +MODULE_DEVICE_TABLE(of, one_bit_adc_dac_dt_match);
> +
> +static struct platform_driver one_bit_adc_dac_driver = {
> + .driver = {
> + .name = "one-bit-adc-dac",
> + .of_match_table = one_bit_adc_dac_dt_match,
> + },
> + .probe = one_bit_adc_dac_probe,
> +};
> +
> +module_platform_driver(one_bit_adc_dac_driver);
> +
> +MODULE_AUTHOR("Cristian Pop <cristian.pop@...log.com>");
> +MODULE_DESCRIPTION("Analog Devices ONE_BIT_ADC_DAC");
> +MODULE_LICENSE("GPL v2");
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