[PATCH v3 0/1] iio: chemical: vz89x: rework i2c transfer reading

[PATCH v3 0/1] iio: chemical: vz89x: rework i2c transfer reading

[Matt Ranostay]

Changes from v2:
* change incorrect i2c_transfer function return check from message length
  to messages executed

Matt Ranostay (1):
  iio: chemical: vz89x: rework i2c transfer reading

 drivers/iio/chemical/vz89x.c | 66 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 52 insertions(+), 14 deletions(-)

-- 
1.9.1

[PATCH v3 1/1] iio: chemical: vz89x: rework i2c transfer reading

[Matt Ranostay]

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>
---
 drivers/iio/chemical/vz89x.c | 66 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 52 insertions(+), 14 deletions(-)

diff --git a/drivers/iio/chemical/vz89x.c b/drivers/iio/chemical/vz89x.c
index 11e59a5..b8b8049 100644
--- 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;
-- 
1.9.1

Re: [PATCH v3 1/1] iio: chemical: vz89x: rework i2c transfer reading

[Jonathan Cameron]

On 02/12/15 05:47, Matt Ranostay wrote:
> 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>
Hmm. The change from V2 is always an interesting one...  Partial transfers
are rather unusual and usually mean thoroughly broken hardware..

Ah well, I don't really care either way so applied this version to the togreg
branch of iio.git - pushed out as testing.
> ---
>  drivers/iio/chemical/vz89x.c | 66 ++++++++++++++++++++++++++++++++++----------
>  1 file changed, 52 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/iio/chemical/vz89x.c b/drivers/iio/chemical/vz89x.c
> index 11e59a5..b8b8049 100644
> --- 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;
>