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 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);
116