On 08/02/2015 11:28 PM, Matt Ranostay wrote:
> On Sun, Aug 2, 2015 at 2:42 AM, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote:
>> On 08/01/2015 05:58 AM, Matt Ranostay wrote:
>> [...]
>>> +
>>> +struct lidar_data {
>>> + struct mutex lock;
>>> + struct iio_dev *indio_dev;
>>> + struct i2c_client *client;
>>> +
>>> + /* config */
>>> + int calib_bias;
>>> +
>>> + u16 buffer[5]; /* 2 byte distance + 8 byte timestamp */
>>
>> Needs to be in its own cacheline to avoid issues if the I2C controller is
>> using DMA.
>
> Ah though this was only needed for SPI.
At least some I2C master drivers directly use the buffer for DMA. But I was
being stupid here anyway, you don't actually pass the buffer itself to the
I2C transfer functions so everything is fine as it was.
>
>>
>> u16 buffer[5] ____cacheline_aligned;
>>
>>> +};
>> [...]
>>> +static inline int lidar_read_byte(struct lidar_data *data, int reg)
>>
>> I'd drop the inline. The compiler is smart enough to figure out whether it
>> makes sense to inline it or not.
>>
> Got it.
>
>>> +{
>>> + struct i2c_client *client = data->client;
>>> + int ret;
>>> +
>>> + ret = i2c_smbus_write_byte(client, reg);
>>> + if (ret < 0) {
>>> + dev_err(&client->dev, "cannot write addr value");
>>> + return ret;
>>> + }
>>> +
>>> + ret = i2c_smbus_read_byte(client);
>>> + if (ret < 0) {
>>> + dev_err(&client->dev, "cannot read data value");
>>> + return ret;
>>> + }
>>
>> Instead of using a write_byte/read_byte combination rather use
>> i2c_smbus_read_byte_data(). I think that will do the same, but in one atomic
>> operation.
> Yes I would normally do that but this device doesn't seem to support
> that functionally, always returns zeros.
That's an interesting device. Maybe add a comment explaining the oddity. I'm
sure I'm not the only one who'll wonder about this.
[...]
>>> +static struct i2c_driver lidar_driver = {
>>> + .driver = {
>>> + .name = LIDAR_DRV_NAME,
>>> + .owner = THIS_MODULE,
>>
>> You added a DT vendor prefix, but there is no of match table for the driver.
>
> So without of_match_table it isn't needed to have a vendor id?
> "pulsedlight,lidar" maps to the i2c_device_id
I thinking the other way around. If you intend to instantiate the device via
devicetree it is better to explicit add a of_device_id table rather than
relying on the implicit mechanism that uses i2c_device_id.
You should also add an entry for the device to
Documentation/devicetree/bindings/i2c/trivial-devices.txt
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