drivers/iio/accel/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
  20 static 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
  47 static 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
  56 static 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
  63 static 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
  90 static const struct spi_device_id bma400_spi_ids[] = {
  91         { "bma400", 0 },
  92         { }
  93 };
  94 MODULE_DEVICE_TABLE(spi, bma400_spi_ids);
  95
  96 static const struct of_device_id bma400_of_spi_match[] = {
  97         { .compatible = "bosch,bma400" },
  98         { }
  99 };
 100 MODULE_DEVICE_TABLE(of, bma400_of_spi_match);
 101
 102 static 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
 111 module_spi_driver(bma400_spi_driver);
 112 MODULE_AUTHOR("Dan Robertson <dan@dlrobertson.com>");
 113 MODULE_DESCRIPTION("Bosch BMA400 triaxial acceleration sensor (SPI)");
 114 MODULE_LICENSE("GPL");
 115 MODULE_IMPORT_NS("IIO_BMA400");