[PATCH] hwmon: (lm75) Add a basic interrupt handler

[Tony O'Brien]

The LM75 interrupt cannot be masked in the device so an over-temperature
event can cause an interrupt that cannot be cleared.
Add an interrupt handler if an interrupt node exists in the DTS for an
LM75.  The handler simply reads a device register to clear the interrupt
and returns.

Signed-off-by: Tony O'Brien <tony.obr...@alliedtelesis.co.nz>
Reviewed-by: Chris Packham <chris.pack...@alliedtelesis.co.nz>
---
 drivers/hwmon/lm75.c | 28 ++++++++++++++++++++++++++++
 drivers/hwmon/lm75.h |  1 +
 2 files changed, 29 insertions(+)

diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
index 005ffb5ffa92..08a833e960aa 100644
--- a/drivers/hwmon/lm75.c
+++ b/drivers/hwmon/lm75.c
@@ -22,6 +22,7 @@
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/jiffies.h>
+#include <linux/interrupt.h>
 #include <linux/i2c.h>
 #include <linux/hwmon.h>
 #include <linux/hwmon-sysfs.h>
@@ -265,6 +266,17 @@ static void lm75_remove(void *data)
        i2c_smbus_write_byte_data(client, LM75_REG_CONF, lm75->orig_conf);
 }
 
+static irqreturn_t lm75_process_interrupt(int irq, void *data)
+{
+       struct i2c_client *client = (struct i2c_client *)data;
+       int val;
+
+       /* Do a read to clear the interrupt */
+       val = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
+
+       return IRQ_HANDLED;
+}
+
 static int
 lm75_probe(struct i2c_client *client, const struct i2c_device_id *id)
 {
@@ -275,6 +287,7 @@ lm75_probe(struct i2c_client *client, const struct 
i2c_device_id *id)
        u8 set_mask, clr_mask;
        int new;
        enum lm75_type kind;
+       int ret;
 
        if (client->dev.of_node)
                kind = (enum lm75_type)of_device_get_match_data(&client->dev);
@@ -375,6 +388,21 @@ lm75_probe(struct i2c_client *client, const struct 
i2c_device_id *id)
                break;
        }
 
+       if (client->irq) {
+               /* If requesting an interrupt then set to interrupt mode */
+               set_mask |= LM75_MODE_INTERRUPT;
+               ret = devm_request_threaded_irq(dev, client->irq, NULL,
+                                               lm75_process_interrupt,
+                                               IRQF_TRIGGER_LOW | IRQF_ONESHOT 
|
+                                                       IRQF_SHARED,
+                                               dev_name(dev),
+                                               client);
+               if (ret) {
+                       dev_err(dev, "Error requesting irq\n");
+                       return ret;
+               }
+       }
+
        /* configure as specified */
        status = i2c_smbus_read_byte_data(client, LM75_REG_CONF);
        if (status < 0) {
diff --git a/drivers/hwmon/lm75.h b/drivers/hwmon/lm75.h
index 5cde94e56f17..82a71d870331 100644
--- a/drivers/hwmon/lm75.h
+++ b/drivers/hwmon/lm75.h
@@ -31,6 +31,7 @@
 #define LM75_TEMP_MIN (-55000)
 #define LM75_TEMP_MAX 125000
 #define LM75_SHUTDOWN 0x01
+#define LM75_MODE_INTERRUPT 0x02
 
 /* TEMP: 0.001C/bit (-55C to +125C)
    REG: (0.5C/bit, two's complement) << 7 */
-- 
2.13.0