minimal driver code

reform2-lpc-driver/Makefile

+KPATH := /usr/src/linux-headers-`uname -r`
+obj-m := ./src/lpc-reform2.o
+
+.PHONY: all clean doc
+
+all:
+	make -C $(KPATH) M=$(CURDIR) modules
+
+clean:
+	make -C $(KPATH) M=$(CURDIR) clean
+
+install:
+	mkdir -p /lib/modules/`uname -r`/misc
+	cp ./src/lpc-reform2.ko /lib/modules/`uname -r`/misc
+	depmod -a
+	modprobe -r lpc-reform2
+	modprobe lpc-reform2
+
+remove:
+	modprobe -r lpc-reform2
+	$(RM) /lib/modules/`uname -r`/misc/lpc-reform2.ko
+	depmod -a
+
+read:
+	cat /sys/bus/spi/drivers/lpc-reform2/spi1.0/status
+

reform2-lpc-driver/src/lpc-reform2.c

+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/mutex.h>
+#include <linux/spi/spi.h>
+#include <linux/delay.h>
+
+static int spiProbe(struct spi_device *spi);
+static void spiRemove(struct spi_device *spi);
+static ssize_t showStatus(struct device *dev, struct device_attribute *attr, char *buf);
+
+typedef struct t_private_data
+{
+    struct spi_device *spi;
+    struct mutex lock;
+} T_PRIVATE_DATA;
+
+static DEVICE_ATTR(status, 0444, showStatus, NULL);
+
+static struct spi_board_info g_spi_board_info = {
+    .modalias = "lpc-reform2",
+    .max_speed_hz = 400000,
+    .bus_num = 0,
+    .chip_select = 0,
+    .mode = SPI_MODE_1,
+};
+
+static int spiProbe(struct spi_device *spi)
+{
+    T_PRIVATE_DATA *data;
+    int ret;
+
+    printk(KERN_INFO "%s: probing ...\n", "lpc-reform2");
+
+    spi->max_speed_hz = g_spi_board_info.max_speed_hz;
+    spi->mode = g_spi_board_info.mode;
+    spi->bits_per_word = 8;
+
+    ret = spi_setup(spi);
+    if (ret)
+    {
+        printk(KERN_ERR "%s: spi_setup failed\n", __func__);
+        return -ENODEV;
+    }
+
+    data = kzalloc(sizeof(T_PRIVATE_DATA), GFP_KERNEL);
+    if (data == NULL)
+    {
+        printk(KERN_ERR "%s: kzalloc failed\n", __func__);
+        return -ENOMEM;
+    }
+
+    data->spi = spi;
+    mutex_init(&data->lock);
+    spi_set_drvdata(spi, data);
+
+    ret = device_create_file(&spi->dev, &dev_attr_status);
+    if (ret)
+    {
+        printk(KERN_ERR "%s: device_create_file failed\n", __func__);
+    }
+
+    return 0;
+}
+
+static void spiRemove(struct spi_device *spi)
+{
+    T_PRIVATE_DATA *data = (T_PRIVATE_DATA *)spi_get_drvdata(spi);
+
+    printk(KERN_INFO "%s: removing ... \n", "lpc-reform2");
+
+    device_remove_file(&spi->dev, &dev_attr_status);
+
+    kfree(data);
+}
+
+static ssize_t showStatus(struct device *dev, struct device_attribute *attr, char *buf)
+{
+    T_PRIVATE_DATA *data = (T_PRIVATE_DATA *)dev_get_drvdata(dev);
+    uint8_t statusCommand[3] = {0xB5, 'q', 0x00};
+    uint8_t statusResult[8];
+    int ret;
+    int16_t voltage;
+    int16_t amps;
+    int8_t percentage;
+    uint8_t status;
+
+    mutex_lock(&data->lock);
+
+    ret = spi_write(data->spi, statusCommand, 3);
+    if (ret)
+    {
+        printk(KERN_INFO "%s: spi_write failed\n", __func__);
+    }
+    mdelay(300);
+
+    ret = spi_read(data->spi, statusResult, 8);
+    if (ret)
+    {
+        printk(KERN_INFO "%s: spi_read failed\n", __func__);
+    }
+
+    mutex_unlock(&data->lock);
+
+    voltage = (int16_t)statusResult[0] | ((int16_t)statusResult[1] << 8);
+    amps = (int16_t)statusResult[2] | ((int16_t)statusResult[3] << 8);
+    percentage = statusResult[4];
+    status = statusResult[5];
+
+    return snprintf(buf, PAGE_SIZE, "%d.%d, %d.%d, %2d%%, %d",
+                    voltage / 1000, voltage % 1000, amps / 1000, abs(amps % 1000), percentage, status);
+}
+
+static const struct of_device_id of_tis_spi_match[] = {
+    {.compatible = "mntre,lpc-reform2", .data = 0},
+    {}};
+MODULE_DEVICE_TABLE(of, of_tis_spi_match);
+
+static struct spi_device_id g_spi_dev_id_list[] = {
+    {"lpc-reform2", 0},
+    {},
+};
+MODULE_DEVICE_TABLE(spi, g_spi_dev_id_list);
+
+static struct spi_driver g_spi_driver = {
+    .probe = spiProbe,
+    .remove = spiRemove,
+    .driver = {
+        .of_match_table = of_match_ptr(of_tis_spi_match),
+        .owner = THIS_MODULE,
+        .name = "lpc-reform2",
+    },
+    .id_table = g_spi_dev_id_list,
+};
+module_spi_driver(g_spi_driver);
+
+MODULE_DESCRIPTION("Reform 2 LPC Driver");
+MODULE_LICENSE("GPL");