cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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max5432.c (3383B)

      1// SPDX-License-Identifier: GPL-2.0-or-later
      2/*
      3 * Maxim Integrated MAX5432-MAX5435 digital potentiometer driver
      4 * Copyright (C) 2019 Martin Kaiser <martin@kaiser.cx>
      5 *
      6 * Datasheet:
      7 * https://datasheets.maximintegrated.com/en/ds/MAX5432-MAX5435.pdf
      8 */
      9
     10#include <linux/i2c.h>
     11#include <linux/iio/iio.h>
     12#include <linux/limits.h>
     13#include <linux/module.h>
     14#include <linux/mod_devicetable.h>
     15#include <linux/property.h>
     16
     17/* All chip variants have 32 wiper positions. */
     18#define MAX5432_MAX_POS 31
     19
     20#define MAX5432_OHM_50K   (50  * 1000)
     21#define MAX5432_OHM_100K  (100 * 1000)
     22
     23/* Update the volatile (currently active) setting. */
     24#define MAX5432_CMD_VREG  0x11
     25
     26struct max5432_data {
     27	struct i2c_client *client;
     28	unsigned long ohm;
     29};
     30
     31static const struct iio_chan_spec max5432_channels[] = {
     32	{
     33		.type = IIO_RESISTANCE,
     34		.indexed = 1,
     35		.output = 1,
     36		.channel = 0,
     37		.address = MAX5432_CMD_VREG,
     38		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
     39		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
     40	}
     41};
     42
     43static int max5432_read_raw(struct iio_dev *indio_dev,
     44			struct iio_chan_spec const *chan,
     45			int *val, int *val2, long mask)
     46{
     47	struct max5432_data *data = iio_priv(indio_dev);
     48
     49	if (mask != IIO_CHAN_INFO_SCALE)
     50		return -EINVAL;
     51
     52	if (unlikely(data->ohm > INT_MAX))
     53		return -ERANGE;
     54
     55	*val = data->ohm;
     56	*val2 = MAX5432_MAX_POS;
     57
     58	return IIO_VAL_FRACTIONAL;
     59}
     60
     61static int max5432_write_raw(struct iio_dev *indio_dev,
     62			struct iio_chan_spec const *chan,
     63			int val, int val2, long mask)
     64{
     65	struct max5432_data *data = iio_priv(indio_dev);
     66	u8 data_byte;
     67
     68	if (mask != IIO_CHAN_INFO_RAW)
     69		return -EINVAL;
     70
     71	if (val < 0 || val > MAX5432_MAX_POS)
     72		return -EINVAL;
     73
     74	if (val2 != 0)
     75		return -EINVAL;
     76
     77	/* Wiper position is in bits D7-D3. (D2-D0 are don't care bits.) */
     78	data_byte = val << 3;
     79	return i2c_smbus_write_byte_data(data->client, chan->address,
     80			data_byte);
     81}
     82
     83static const struct iio_info max5432_info = {
     84	.read_raw = max5432_read_raw,
     85	.write_raw = max5432_write_raw,
     86};
     87
     88static int max5432_probe(struct i2c_client *client,
     89		const struct i2c_device_id *id)
     90{
     91	struct device *dev = &client->dev;
     92	struct iio_dev *indio_dev;
     93	struct max5432_data *data;
     94
     95	indio_dev = devm_iio_device_alloc(dev, sizeof(struct max5432_data));
     96	if (!indio_dev)
     97		return -ENOMEM;
     98
     99	i2c_set_clientdata(client, indio_dev);
    100
    101	data = iio_priv(indio_dev);
    102	data->client = client;
    103	data->ohm = (unsigned long)device_get_match_data(dev);
    104
    105	indio_dev->info = &max5432_info;
    106	indio_dev->channels = max5432_channels;
    107	indio_dev->num_channels = ARRAY_SIZE(max5432_channels);
    108	indio_dev->name = client->name;
    109
    110	return devm_iio_device_register(dev, indio_dev);
    111}
    112
    113static const struct of_device_id max5432_dt_ids[] = {
    114	{ .compatible = "maxim,max5432", .data = (void *)MAX5432_OHM_50K  },
    115	{ .compatible = "maxim,max5433", .data = (void *)MAX5432_OHM_100K },
    116	{ .compatible = "maxim,max5434", .data = (void *)MAX5432_OHM_50K  },
    117	{ .compatible = "maxim,max5435", .data = (void *)MAX5432_OHM_100K },
    118	{ /* sentinel */ }
    119};
    120MODULE_DEVICE_TABLE(of, max5432_dt_ids);
    121
    122static struct i2c_driver max5432_driver = {
    123	.driver = {
    124		.name = "max5432",
    125		.of_match_table = max5432_dt_ids,
    126	},
    127	.probe = max5432_probe,
    128};
    129
    130module_i2c_driver(max5432_driver);
    131
    132MODULE_AUTHOR("Martin Kaiser <martin@kaiser.cx>");
    133MODULE_DESCRIPTION("max5432-max5435 digital potentiometers");
    134MODULE_LICENSE("GPL v2");