[PATCH] lm70: New hardware monitoring driver

This driver implements support for the National Semiconductor LM70
temperature sensor.

The LM70 temperature sensor chip supports a single temperature sensor.
It communicates with a host processor (or microcontroller) via an
SPI/Microwire Bus interface.

Communication with the LM70 is simple: when the temperature is to be sensed,
the driver accesses the LM70 using SPI communication: 16 SCLK cycles
comprise the MOSI/MISO loop. At the end of the transfer, the 11-bit 2's
complement digital temperature (sent via the SIO line), is available in the
driver for interpretation. This driver makes use of the kernel's in-core
SPI support.

Signed-off-by: Kaiwan N Billimoria <kaiwan@designergraphix.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 165 insertions, 0 deletions

diff --git a/drivers/hwmon/lm70.c b/drivers/hwmon/lm70.c
new file mode 100644
index 000000000000..6ba84731b9cd
--- /dev/null
+++ b/drivers/hwmon/lm70.c
@@ -0,0 +1,165 @@
+/*
+ * lm70.c
+ *
+ * The LM70 is a temperature sensor chip from National Semiconductor (NS).
+ * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
+ *
+ * The LM70 communicates with a host processor via an SPI/Microwire Bus
+ * interface. The complete datasheet is available at National's website
+ * here:
+ * http://www.national.com/pf/LM/LM70.html
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/sysfs.h>
+#include <linux/hwmon.h>
+#include <linux/spi/spi.h>
+#include <asm/semaphore.h>
+
+#define DRVNAME         "lm70"
+
+struct lm70 {
+        struct class_device *cdev;
+        struct semaphore sem;
+};
+
+/* sysfs hook function */
+static ssize_t lm70_sense_temp(struct device *dev,
+                struct device_attribute *attr, char *buf)
+{
+        struct spi_device *spi = to_spi_device(dev);
+        int status, val;
+        u8 rxbuf[2];
+        s16 raw=0;
+        struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
+
+        if (down_interruptible(&p_lm70->sem))
+                return -ERESTARTSYS;
+
+        /*
+         * spi_read() requires a DMA-safe buffer; so we use
+         * spi_write_then_read(), transmitting 0 bytes.
+         */
+        status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
+        if (status < 0) {
+                printk(KERN_WARNING
+                "spi_write_then_read failed with status %d\n", status);
+                goto out;
+        }
+        dev_dbg(dev, "rxbuf[1] : 0x%x rxbuf[0] : 0x%x\n", rxbuf[1], rxbuf[0]);
+
+        raw = (rxbuf[1] << 8) + rxbuf[0];
+        dev_dbg(dev, "raw=0x%x\n", raw);
+
+        /*
+         * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
+         * complement value. Only the MSB 11 bits (1 sign + 10 temperature
+         * bits) are meaningful; the LSB 5 bits are to be discarded.
+         * See the datasheet.
+         *
+         * Further, each bit represents 0.25 degrees Celsius; so, multiply
+         * by 0.25. Also multiply by 1000 to represent in millidegrees
+         * Celsius.
+         * So it's equivalent to multiplying by 0.25 * 1000 = 250.
+         */
+        val = ((int)raw/32) * 250;
+        status = sprintf(buf, "%+d\n", val); /* millidegrees Celsius */
+out:
+        up(&p_lm70->sem);
+        return status;
+}
+
+static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
+
+/*----------------------------------------------------------------------*/
+
+static int __devinit lm70_probe(struct spi_device *spi)
+{
+        struct lm70 *p_lm70;
+        int status;
+
+        p_lm70 = kzalloc(sizeof *p_lm70, GFP_KERNEL);
+        if (!p_lm70)
+                return -ENOMEM;
+
+        init_MUTEX(&p_lm70->sem);
+
+        /* sysfs hook */
+        p_lm70->cdev = hwmon_device_register(&spi->dev);
+        if (IS_ERR(p_lm70->cdev)) {
+                dev_dbg(&spi->dev, "hwmon_device_register failed.\n");
+                status = PTR_ERR(p_lm70->cdev);
+                goto out_dev_reg_failed;
+        }
+        dev_set_drvdata(&spi->dev, p_lm70);
+
+        if ((status = device_create_file(&spi->dev, &dev_attr_temp1_input))) {
+                dev_dbg(&spi->dev, "device_create_file failure.\n");
+                goto out_dev_create_file_failed;
+        }
+
+        return 0;
+
+out_dev_create_file_failed:
+        hwmon_device_unregister(p_lm70->cdev);
+out_dev_reg_failed:
+        dev_set_drvdata(&spi->dev, NULL);
+        kfree(p_lm70);
+        return status;
+}
+
+static int __exit lm70_remove(struct spi_device *spi)
+{
+        struct lm70 *p_lm70 = dev_get_drvdata(&spi->dev);
+
+        device_remove_file(&spi->dev, &dev_attr_temp1_input);
+        hwmon_device_unregister(p_lm70->cdev);
+        dev_set_drvdata(&spi->dev, NULL);
+        kfree(p_lm70);
+
+        return 0;
+}
+
+static struct spi_driver lm70_driver = {
+        .driver = {
+                .name   = "lm70",
+                .owner  = THIS_MODULE,
+        },
+        .probe  = lm70_probe,
+        .remove = __devexit_p(lm70_remove),
+};
+
+static int __init init_lm70(void)
+{
+        return spi_register_driver(&lm70_driver);
+}
+
+static void __exit cleanup_lm70(void)
+{
+        spi_unregister_driver(&lm70_driver);
+}
+
+module_init(init_lm70);
+module_exit(cleanup_lm70);
+
+MODULE_AUTHOR("Kaiwan N Billimoria");
+MODULE_DESCRIPTION("National Semiconductor LM70 Linux driver");
+MODULE_LICENSE("GPL");