Re: [RFC PATCH] iio: accel: kxcj: Reconcile operation order between iio_register/unregister and pm functions

[Lars-Peter Clausen <lars@metafoo.de>]

On 11/04/2015 05:42 PM, Adriana Reus wrote:
> At probe runtime pm should be setup before registering the sysfs interface.
> Also when removing the device we should unregister first to make sure
> that the interfaces that may result in wakeups etc are no longer available.
> 
> Signed-off-by: Adriana Reus <adriana.reus@intel.com>
> ---
>  I remember having a conversation on the order of iio_unregister
>  and pm disable functions (http://www.spinics.net/lists/linux-iio/msg19606.html)
>  and why it is best that unregister is the first call in remove.
>  Also I'm thinking that at probe it would be best to enable runtime pm before 
>  exposing it in sysfs for the (theoretical) case when pm attributes might be checked before
>  they update. I noticed that a lot of drivers do it the other way around and I'm not sure 
>  if maybe there's a reason for this that I am missing.
> 
>  If this is reasonable I can send patches for the other drivers also 
>  (bmc150, bmg160, kmx and some other ones)

Yes, looks good. Once iio_device_register() has succeeded the device is live
and can be accessed at any point there after, this means all resources
required for operation must have be acquired at that point. Similar
iio_device_unregister() makes sure that the device can't any longer be
accessed after the call has succeeded, so resources may only be freed after
that.


The order must always be

in probe:

iio_device_alloc()

acquire all resources required for proper device operation

iio_device_register()

in remove:

iio_device_unregister()

release any resources associated with the device

iio_device_free()

> 
>  drivers/iio/accel/kxcjk-1013.c | 20 +++++++++-----------
>  1 file changed, 9 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/iio/accel/kxcjk-1013.c b/drivers/iio/accel/kxcjk-1013.c
> index 18c1b06..edec1d0 100644
> --- a/drivers/iio/accel/kxcjk-1013.c
> +++ b/drivers/iio/accel/kxcjk-1013.c
> @@ -1264,25 +1264,23 @@ static int kxcjk1013_probe(struct i2c_client *client,
>  		goto err_trigger_unregister;
>  	}
>  
> -	ret = iio_device_register(indio_dev);
> -	if (ret < 0) {
> -		dev_err(&client->dev, "unable to register iio device\n");
> -		goto err_buffer_cleanup;
> -	}
> -
>  	ret = pm_runtime_set_active(&client->dev);
>  	if (ret)
> -		goto err_iio_unregister;
> +		goto err_buffer_cleanup;
>  
>  	pm_runtime_enable(&client->dev);
>  	pm_runtime_set_autosuspend_delay(&client->dev,
>  					 KXCJK1013_SLEEP_DELAY_MS);
>  	pm_runtime_use_autosuspend(&client->dev);
>  
> +	ret = iio_device_register(indio_dev);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "unable to register iio device\n");
> +		goto err_buffer_cleanup;
> +	}
> +
>  	return 0;
>  
> -err_iio_unregister:
> -	iio_device_unregister(indio_dev);
>  err_buffer_cleanup:
>  	if (data->dready_trig)
>  		iio_triggered_buffer_cleanup(indio_dev);
> @@ -1302,12 +1300,12 @@ static int kxcjk1013_remove(struct i2c_client *client)
>  	struct iio_dev *indio_dev = i2c_get_clientdata(client);
>  	struct kxcjk1013_data *data = iio_priv(indio_dev);
>  
> +	iio_device_unregister(indio_dev);
> +
>  	pm_runtime_disable(&client->dev);
>  	pm_runtime_set_suspended(&client->dev);
>  	pm_runtime_put_noidle(&client->dev);
>  
> -	iio_device_unregister(indio_dev);
> -
>  	if (data->dready_trig) {
>  		iio_triggered_buffer_cleanup(indio_dev);
>  		iio_trigger_unregister(data->dready_trig);
>