bma400_spi.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * SPI IIO driver for Bosch BMA400 triaxial acceleration sensor.
  4 *
  5 * Copyright 2020 Dan Robertson <dan@dlrobertson.com>
  6 *
  7 */
  8#include <linux/bits.h>
  9#include <linux/init.h>
 10#include <linux/mod_devicetable.h>
 11#include <linux/module.h>
 12#include <linux/regmap.h>
 13#include <linux/spi/spi.h>
 14
 15#include "bma400.h"
 16
 17#define BMA400_MAX_SPI_READ 2
 18#define BMA400_SPI_READ_BUFFER_SIZE (BMA400_MAX_SPI_READ + 1)
 19
 20static int bma400_regmap_spi_read(void *context,
 21				  const void *reg, size_t reg_size,
 22				  void *val, size_t val_size)
 23{
 24	struct device *dev = context;
 25	struct spi_device *spi = to_spi_device(dev);
 26	u8 result[BMA400_SPI_READ_BUFFER_SIZE];
 27	ssize_t status;
 28
 29	if (val_size > BMA400_MAX_SPI_READ)
 30		return -EINVAL;
 31
 32	status = spi_write_then_read(spi, reg, 1, result, val_size + 1);
 33	if (status)
 34		return status;
 35
 36	/*
 37	 * From the BMA400 datasheet:
 38	 *
 39	 * > For a basic read operation two bytes have to be read and the first
 40	 * > has to be dropped and the second byte must be interpreted.
 41	 */
 42	memcpy(val, result + 1, val_size);
 43
 44	return 0;
 45}
 46
 47static int bma400_regmap_spi_write(void *context, const void *data,
 48				   size_t count)
 49{
 50	struct device *dev = context;
 51	struct spi_device *spi = to_spi_device(dev);
 52
 53	return spi_write(spi, data, count);
 54}
 55
 56static const struct regmap_bus bma400_regmap_bus = {
 57	.read = bma400_regmap_spi_read,
 58	.write = bma400_regmap_spi_write,
 59	.read_flag_mask = BIT(7),
 60	.max_raw_read = BMA400_MAX_SPI_READ,
 61};
 62
 63static int bma400_spi_probe(struct spi_device *spi)
 64{
 65	const struct spi_device_id *id = spi_get_device_id(spi);
 66	struct regmap *regmap;
 67	unsigned int val;
 68	int ret;
 69
 70	regmap = devm_regmap_init(&spi->dev, &bma400_regmap_bus,
 71				  &spi->dev, &bma400_regmap_config);
 72	if (IS_ERR(regmap)) {
 73		dev_err(&spi->dev, "failed to create regmap\n");
 74		return PTR_ERR(regmap);
 75	}
 76
 77	/*
 78	 * Per the bma400 datasheet, the first SPI read may
 79	 * return garbage. As the datasheet recommends, the
 80	 * chip ID register will be read here and checked
 81	 * again in the following probe.
 82	 */
 83	ret = regmap_read(regmap, BMA400_CHIP_ID_REG, &val);
 84	if (ret)
 85		dev_err(&spi->dev, "Failed to read chip id register\n");
 86
 87	return bma400_probe(&spi->dev, regmap, spi->irq, id->name);
 88}
 89
 90static const struct spi_device_id bma400_spi_ids[] = {
 91	{ "bma400", 0 },
 92	{ }
 93};
 94MODULE_DEVICE_TABLE(spi, bma400_spi_ids);
 95
 96static const struct of_device_id bma400_of_spi_match[] = {
 97	{ .compatible = "bosch,bma400" },
 98	{ }
 99};
100MODULE_DEVICE_TABLE(of, bma400_of_spi_match);
101
102static struct spi_driver bma400_spi_driver = {
103	.driver = {
104		.name = "bma400",
105		.of_match_table = bma400_of_spi_match,
106	},
107	.probe    = bma400_spi_probe,
108	.id_table = bma400_spi_ids,
109};
110
111module_spi_driver(bma400_spi_driver);
112MODULE_AUTHOR("Dan Robertson <dan@dlrobertson.com>");
113MODULE_DESCRIPTION("Bosch BMA400 triaxial acceleration sensor (SPI)");
114MODULE_LICENSE("GPL");
115MODULE_IMPORT_NS("IIO_BMA400");