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Date: Thu, 20 Oct 2011 08:12:46 -0700
From: Guenter Roeck <guenter.roeck@...csson.com>
To: Jonathan Cameron <jic23@....ac.uk>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
"linus.ml.walleij@...il.com" <linus.ml.walleij@...il.com>,
"zdevai@...il.com" <zdevai@...il.com>,
"linux@....linux.org.uk" <linux@....linux.org.uk>,
"arnd@...db.de" <arnd@...db.de>,
"broonie@...nsource.wolfsonmicro.com"
<broonie@...nsource.wolfsonmicro.com>,
"gregkh@...e.de" <gregkh@...e.de>,
"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
"khali@...ux-fr.org" <khali@...ux-fr.org>,
"thomas.petazzoni@...e-electrons.com"
<thomas.petazzoni@...e-electrons.com>,
"maxime.ripard@...e-electrons.com" <maxime.ripard@...e-electrons.com>
Subject: Re: [PATCH 5/6] IIO:hwmon interface client driver.
On Thu, 2011-10-20 at 05:33 -0400, Jonathan Cameron wrote:
> Should move to drivers/hwmon once people are happy with it.
>
> Minimal support of simple in, curr and temp attributes
> so far.
>
> Signed-off-by: Jonathan Cameron <jic23@....ac.uk>
> ---
> drivers/iio/Kconfig | 8 ++
> drivers/iio/Makefile | 1 +
> drivers/iio/iio_hwmon.c | 227 +++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 236 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
> index 308bc97..c2f0970 100644
> --- a/drivers/iio/Kconfig
> +++ b/drivers/iio/Kconfig
> @@ -11,6 +11,14 @@ menuconfig IIO
>
> if IIO
>
> +config IIO_HWMON
> + tristate "Hwmon driver that uses channels specified via iio maps"
> + depends on HWMON
> + help
> + This is a platform driver that in combination with a suitable
> + map allows IIO devices to provide basic hwmon functionality
> + for those channels specified in the map.
> +
> source "drivers/iio/adc/Kconfig"
> source "drivers/iio/imu/Kconfig"
> source "drivers/iio/light/Kconfig"
> diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
> index cfb588a..5f9c01a 100644
> --- a/drivers/iio/Makefile
> +++ b/drivers/iio/Makefile
> @@ -6,6 +6,7 @@ obj-y = inkern.o
> obj-$(CONFIG_IIO) += iio.o
> industrialio-y := core.o
>
> +obj-$(CONFIG_IIO_HWMON) += iio_hwmon.o
> obj-y += adc/
> obj-y += imu/
> obj-y += light/
> diff --git a/drivers/iio/iio_hwmon.c b/drivers/iio/iio_hwmon.c
> new file mode 100644
> index 0000000..b3348ad
> --- /dev/null
> +++ b/drivers/iio/iio_hwmon.c
> @@ -0,0 +1,227 @@
> +/* Hwmon client for industrial I/O devices
> + *
> + * Copyright (c) 2011 Jonathan Cameron
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published by
> + * the Free Software Foundation.
> + *
> + * Limited functionality currently supported.
Just nitpicking ... this comment doesn't provide much value. It doesn't
explain the limits, nor what could be improved.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/module.h>
> +#include <linux/err.h>
> +#include <linux/platform_device.h>
> +#include <linux/iio/inkern.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
> +
> +/**
> + * struct iio_hwmon_state - device instance state
> + * @channels: filled with null terminated array of channels from iio
> + * @num_channels: number of channels in channels (saves counting twice)
> + * @hwmon_dev: associated hwmon device
> + * @attr_group: the group of attributes
> + * @attrs: null terminated array of attribute pointers.
> + */
> +struct iio_hwmon_state {
> + struct iio_channel **channels;
> + int num_channels;
> + struct device *hwmon_dev;
> + struct attribute_group attr_group;
> + struct attribute **attrs;
> +};
> +
> +/*
> + * Assumes that IIO and hwmon operate in the same base units.
> + * This is supposed to be true, but needs verification for
> + * new channel types.
> + */
> +static ssize_t iio_hwmon_read_val(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + long result;
> + int val, ret, scaleint, scalepart;
> + struct sensor_device_attribute *sattr = to_sensor_dev_attr(attr);
> + struct iio_hwmon_state *state = dev_get_drvdata(dev);
> +
> + /*
> + * No locking between this pair, so theoretically possible
> + * the scale has changed.
> + */
> + ret = iio_read_channel_raw(state->channels[sattr->index],
> + &val);
> + if (ret < 0)
> + return ret;
> +
> + ret = iio_read_channel_scale(state->channels[sattr->index],
> + &scaleint, &scalepart);
> + if (ret < 0)
> + return ret;
> + switch (ret) {
> + case IIO_VAL_INT:
> + result = val * scaleint;
> + break;
> + case IIO_VAL_INT_PLUS_MICRO:
> + result = (long)val * (long)scaleint +
> + (long)val * (long)scalepart / 1000000L;
> + break;
> + case IIO_VAL_INT_PLUS_NANO:
> + result = (long)val * (long)scaleint +
> + (long)val * (long)scalepart / 1000000000L;
> + break;
Still easy to imagine that val * scalepart gets larger than 2147483647L
(on machines where sizeof(long) = 4) ... it will already happen if the
result of (val * scalepart / 1000000000) is larger than 2.
What value range do you expect to see here ?
If (val * scaleint) is already the milli-unit, scalepart would possibly
only address fractions of milli-units. If so, the result of (val *
scalepart / 1000000000L) might always be smaller than 1, ie 0. If so,
for the calculation to have any value, you might be better off using
DIV_ROUND_CLOSEST(val * scalepart, 1000000000L).
I am a bit confused by this anyway. Since hwmon in general reports
milli-units, VAL_INT appears to reflect milli-units, VAL_INT_PLUS_MICRO
really means nano-units, and IIO_VAL_INT_PLUS_NANO really means
pico-units. Is this correct ?
> + default:
> + return -EINVAL;
> + }
> + return sprintf(buf, "%ld\n", result);
> +}
> +
> +static void iio_hwmon_free_attrs(struct iio_hwmon_state *st)
> +{
> + int i;
> + struct sensor_device_attribute *a;
> + for (i = 0; i < st->num_channels; i++)
> + if (st->attrs[i]) {
> + a = to_sensor_dev_attr(
> + container_of(st->attrs[i],
> + struct device_attribute,
> + attr));
> + kfree(a);
> + }
> +}
> +
> +static int __devinit iio_hwmon_probe(struct platform_device *pdev)
> +{
> + struct iio_hwmon_state *st;
> + struct sensor_device_attribute *a;
> + int ret, i;
> + int in_i = 1, temp_i = 1, curr_i = 1;
> +
> + st = kzalloc(sizeof(*st), GFP_KERNEL);
> + if (st == NULL) {
> + ret = -ENOMEM;
> + goto error_ret;
> + }
> +
> + st->channels = iio_channel_get_all(&pdev->dev, NULL);
> + if (IS_ERR(st->channels)) {
> + ret = PTR_ERR(st->channels);
> + goto error_free_state;
> + }
> +
> + /* count how many attributes we have */
> + while (st->channels[st->num_channels])
> + st->num_channels++;
> +
> + st->attrs = kzalloc(sizeof(st->attrs) * (st->num_channels + 1),
> + GFP_KERNEL);
Why "+ 1" ?
Unless I am missing something, you only use st->attrs[0] ..
st->attrs[st->num_channels-1].
Thanks,
Guenter
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