iio: chemical: vz89x: rework i2c transfer reading

Add an optimized i2c transfer reading function, and fallback
to racey smbus transfers if client->adapter doesn't support this.

Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/chemical/vz89x.c b/drivers/iio/chemical/vz89x.c
index 11e59a5..b8b8049 100644 (file)
--- a/drivers/iio/chemical/vz89x.c
+++ b/drivers/iio/chemical/vz89x.c
@@ -34,8 +34,9 @@
 struct vz89x_data {
        struct i2c_client *client;
        struct mutex lock;
-       unsigned long last_update;
+       int (*xfer)(struct vz89x_data *data, u8 cmd);
 
+       unsigned long last_update;
        u8 buffer[VZ89X_REG_MEASUREMENT_SIZE];
 };
 
@@ -100,27 +101,60 @@ static int vz89x_measurement_is_valid(struct vz89x_data *data)
        return !!(data->buffer[VZ89X_REG_MEASUREMENT_SIZE - 1] > 0);
 }
 
-static int vz89x_get_measurement(struct vz89x_data *data)
+static int vz89x_i2c_xfer(struct vz89x_data *data, u8 cmd)
 {
+       struct i2c_client *client = data->client;
+       struct i2c_msg msg[2];
        int ret;
-       int i;
+       u8 buf[3] = { cmd, 0, 0};
 
-       /* sensor can only be polled once a second max per datasheet */
-       if (!time_after(jiffies, data->last_update + HZ))
-               return 0;
+       msg[0].addr = client->addr;
+       msg[0].flags = client->flags;
+       msg[0].len = 3;
+       msg[0].buf  = (char *) &buf;
+
+       msg[1].addr = client->addr;
+       msg[1].flags = client->flags | I2C_M_RD;
+       msg[1].len = VZ89X_REG_MEASUREMENT_SIZE;
+       msg[1].buf = (char *) &data->buffer;
+
+       ret = i2c_transfer(client->adapter, msg, 2);
 
-       ret = i2c_smbus_write_word_data(data->client,
-                                       VZ89X_REG_MEASUREMENT, 0);
+       return (ret == 2) ? 0 : ret;
+}
+
+static int vz89x_smbus_xfer(struct vz89x_data *data, u8 cmd)
+{
+       struct i2c_client *client = data->client;
+       int ret;
+       int i;
+
+       ret = i2c_smbus_write_word_data(client, cmd, 0);
        if (ret < 0)
                return ret;
 
        for (i = 0; i < VZ89X_REG_MEASUREMENT_SIZE; i++) {
-               ret = i2c_smbus_read_byte(data->client);
+               ret = i2c_smbus_read_byte(client);
                if (ret < 0)
                        return ret;
                data->buffer[i] = ret;
        }
 
+       return 0;
+}
+
+static int vz89x_get_measurement(struct vz89x_data *data)
+{
+       int ret;
+
+       /* sensor can only be polled once a second max per datasheet */
+       if (!time_after(jiffies, data->last_update + HZ))
+               return 0;
+
+       ret = data->xfer(data, VZ89X_REG_MEASUREMENT);
+       if (ret < 0)
+               return ret;
+
        ret = vz89x_measurement_is_valid(data);
        if (ret)
                return -EAGAIN;
@@ -204,15 +238,19 @@ static int vz89x_probe(struct i2c_client *client,
        struct iio_dev *indio_dev;
        struct vz89x_data *data;
 
-       if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA |
-                                    I2C_FUNC_SMBUS_BYTE))
-               return -ENODEV;
-
        indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
        if (!indio_dev)
                return -ENOMEM;
-
        data = iio_priv(indio_dev);
+
+       if (i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+               data->xfer = vz89x_i2c_xfer;
+       else if (i2c_check_functionality(client->adapter,
+                               I2C_FUNC_SMBUS_WORD_DATA | I2C_FUNC_SMBUS_BYTE))
+               data->xfer = vz89x_smbus_xfer;
+       else
+               return -ENOTSUPP;
+
        i2c_set_clientdata(client, indio_dev);
        data->client = client;
        data->last_update = jiffies - HZ;