Date:   Tue, 30 Mar 2021 13:51:13 +0100
From:   Cristian Marussi <cristian.marussi@....com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        sudeep.holla@....com, lukasz.luba@....com,
        james.quinlan@...adcom.com, f.fainelli@...il.com,
        etienne.carriere@...aro.org, thara.gopinath@...aro.org,
        vincent.guittot@...aro.org, souvik.chakravarty@....com,
        Jyoti Bhayana <jbhayana@...gle.com>,
        Jonathan Cameron <jic23@...nel.org>, linux-iio@...r.kernel.org
Subject: Re: [PATCH v7 25/38] iio/scmi: port driver to the new
 scmi_sensor_proto_ops interface

Hi Jonathan,

On Tue, Mar 30, 2021 at 12:33:25PM +0100, Jonathan Cameron wrote:
> On Tue, 16 Mar 2021 12:48:50 +0000
> Cristian Marussi <cristian.marussi@....com> wrote:
> 
> > Port driver to the new SCMI Sensor interface based on protocol handles
> > and common devm_get_ops().
> > 
> > Cc: Jyoti Bhayana <jbhayana@...gle.com>
> > Cc: Jonathan Cameron <jic23@...nel.org>
> > Signed-off-by: Cristian Marussi <cristian.marussi@....com>
> 
> +CC linux-iio@...r.kernel.org
> 
> Rule of thumb if it doesn't go there it ends up in randomly location based
> on other lists and I might not see it for a few weeks :(
> 

Ah sorry, I thought the direct CC was enough.

> > ---
> >  drivers/iio/common/scmi_sensors/scmi_iio.c | 91 ++++++++++------------
> >  1 file changed, 41 insertions(+), 50 deletions(-)
> > 
> > diff --git a/drivers/iio/common/scmi_sensors/scmi_iio.c b/drivers/iio/common/scmi_sensors/scmi_iio.c
> > index 872d87ca6256..b4bdc3f3a946 100644
> > --- a/drivers/iio/common/scmi_sensors/scmi_iio.c
> > +++ b/drivers/iio/common/scmi_sensors/scmi_iio.c
> > @@ -21,8 +21,10 @@
> >  
> >  #define SCMI_IIO_NUM_OF_AXIS 3
> >  
> > +static const struct scmi_sensor_proto_ops *sensor_ops;
> 
> Hmm.   I'm not keen on globals when they really should not be necessary.
> They just result in lifetimes being out of sync.  Here you are fine because
> you set it to an appropriate value as the first thing you do in probe, and
> I assume the function only ever returns on answer on repeated calls.
> 
> Why not put a copy of that pointer inside the struct scmi_iio_priv structures?
> 

The reason for this, as I said to Jyoyi who made the same comment indeed,
from my point of view (maybe wrong..) was that while the protocol_handle,
and previously the handle, are 'per-instance data' (so that you get a
different one each time this driver is possibly probed against a different
platform-handle) and as such are stored in scmi_iio_priv, the _ops are
just plain code pointers and are returned always the same for the same
protocol no matter how many times you probe this driver: you just end up
calling them against the proper different saved protocol_handle; so it
seemed to me an unneeded duplication to stick a copy of the same _ops
inside each per-instance scmi_iio_priv, and at the same time it seemed
also more straigthforward to access them without too many indirections
from inside the scmi_iio_priv struct).

But if these are not valid points I can change this in IIO now, and in
the future also in all the other SCMI drivers that currently use this
same API and pattern of usage with global ops. (..at least because I'd
have to collect again all the other ACks agains and it's a bit later for
that now)

Thanks

Cristian

> Otherwise this all looks like straight forward refactoring so given the
> above is more a 'bad smell' than a bug and I'm rather late to the game.
> 
> Acked-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> 
> 
> > +
> >  struct scmi_iio_priv {
> > -	struct scmi_handle *handle;
> > +	struct scmi_protocol_handle *ph;
> >  	const struct scmi_sensor_info *sensor_info;
> >  	struct iio_dev *indio_dev;
> >  	/* adding one additional channel for timestamp */
> > @@ -82,7 +84,6 @@ static int scmi_iio_sensor_update_cb(struct notifier_block *nb,
> >  static int scmi_iio_buffer_preenable(struct iio_dev *iio_dev)
> >  {
> >  	struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > -	u32 sensor_id = sensor->sensor_info->id;
> >  	u32 sensor_config = 0;
> >  	int err;
> >  
> > @@ -92,27 +93,11 @@ static int scmi_iio_buffer_preenable(struct iio_dev *iio_dev)
> >  
> >  	sensor_config |= FIELD_PREP(SCMI_SENS_CFG_SENSOR_ENABLED_MASK,
> >  				    SCMI_SENS_CFG_SENSOR_ENABLE);
> > -
> > -	err = sensor->handle->notify_ops->register_event_notifier(sensor->handle,
> > -			SCMI_PROTOCOL_SENSOR, SCMI_EVENT_SENSOR_UPDATE,
> > -			&sensor_id, &sensor->sensor_update_nb);
> > -	if (err) {
> > -		dev_err(&iio_dev->dev,
> > -			"Error in registering sensor update notifier for sensor %s err %d",
> > -			sensor->sensor_info->name, err);
> > -		return err;
> > -	}
> > -
> > -	err = sensor->handle->sensor_ops->config_set(sensor->handle,
> > -			sensor->sensor_info->id, sensor_config);
> > -	if (err) {
> > -		sensor->handle->notify_ops->unregister_event_notifier(sensor->handle,
> > -				SCMI_PROTOCOL_SENSOR,
> > -				SCMI_EVENT_SENSOR_UPDATE, &sensor_id,
> > -				&sensor->sensor_update_nb);
> > +	err = sensor_ops->config_set(sensor->ph, sensor->sensor_info->id,
> > +				     sensor_config);
> > +	if (err)
> >  		dev_err(&iio_dev->dev, "Error in enabling sensor %s err %d",
> >  			sensor->sensor_info->name, err);
> > -	}
> >  
> >  	return err;
> >  }
> > @@ -120,25 +105,13 @@ static int scmi_iio_buffer_preenable(struct iio_dev *iio_dev)
> >  static int scmi_iio_buffer_postdisable(struct iio_dev *iio_dev)
> >  {
> >  	struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > -	u32 sensor_id = sensor->sensor_info->id;
> >  	u32 sensor_config = 0;
> >  	int err;
> >  
> >  	sensor_config |= FIELD_PREP(SCMI_SENS_CFG_SENSOR_ENABLED_MASK,
> >  				    SCMI_SENS_CFG_SENSOR_DISABLE);
> > -
> > -	err = sensor->handle->notify_ops->unregister_event_notifier(sensor->handle,
> > -			SCMI_PROTOCOL_SENSOR, SCMI_EVENT_SENSOR_UPDATE,
> > -			&sensor_id, &sensor->sensor_update_nb);
> > -	if (err) {
> > -		dev_err(&iio_dev->dev,
> > -			"Error in unregistering sensor update notifier for sensor %s err %d",
> > -			sensor->sensor_info->name, err);
> > -		return err;
> > -	}
> > -
> > -	err = sensor->handle->sensor_ops->config_set(sensor->handle, sensor_id,
> > -						     sensor_config);
> > +	err = sensor_ops->config_set(sensor->ph, sensor->sensor_info->id,
> > +				     sensor_config);
> >  	if (err) {
> >  		dev_err(&iio_dev->dev,
> >  			"Error in disabling sensor %s with err %d",
> > @@ -161,8 +134,8 @@ static int scmi_iio_set_odr_val(struct iio_dev *iio_dev, int val, int val2)
> >  	u32 sensor_config;
> >  	char buf[32];
> >  
> > -	int err = sensor->handle->sensor_ops->config_get(sensor->handle,
> > -			sensor->sensor_info->id, &sensor_config);
> > +	int err = sensor_ops->config_get(sensor->ph, sensor->sensor_info->id,
> > +					 &sensor_config);
> >  	if (err) {
> >  		dev_err(&iio_dev->dev,
> >  			"Error in getting sensor config for sensor %s err %d",
> > @@ -208,8 +181,8 @@ static int scmi_iio_set_odr_val(struct iio_dev *iio_dev, int val, int val2)
> >  	sensor_config |=
> >  		FIELD_PREP(SCMI_SENS_CFG_ROUND_MASK, SCMI_SENS_CFG_ROUND_AUTO);
> >  
> > -	err = sensor->handle->sensor_ops->config_set(sensor->handle,
> > -			sensor->sensor_info->id, sensor_config);
> > +	err = sensor_ops->config_set(sensor->ph, sensor->sensor_info->id,
> > +				     sensor_config);
> >  	if (err)
> >  		dev_err(&iio_dev->dev,
> >  			"Error in setting sensor update interval for sensor %s value %u err %d",
> > @@ -274,8 +247,8 @@ static int scmi_iio_get_odr_val(struct iio_dev *iio_dev, int *val, int *val2)
> >  	u32 sensor_config;
> >  	int mult;
> >  
> > -	int err = sensor->handle->sensor_ops->config_get(sensor->handle,
> > -			sensor->sensor_info->id, &sensor_config);
> > +	int err = sensor_ops->config_get(sensor->ph, sensor->sensor_info->id,
> > +					 &sensor_config);
> >  	if (err) {
> >  		dev_err(&iio_dev->dev,
> >  			"Error in getting sensor config for sensor %s err %d",
> > @@ -542,15 +515,17 @@ static int scmi_iio_buffers_setup(struct iio_dev *scmi_iiodev)
> >  	return 0;
> >  }
> >  
> > -static struct iio_dev *scmi_alloc_iiodev(struct device *dev,
> > -					 struct scmi_handle *handle,
> > -					 const struct scmi_sensor_info *sensor_info)
> > +static struct iio_dev *
> > +scmi_alloc_iiodev(struct scmi_device *sdev, struct scmi_protocol_handle *ph,
> > +		  const struct scmi_sensor_info *sensor_info)
> >  {
> >  	struct iio_chan_spec *iio_channels;
> >  	struct scmi_iio_priv *sensor;
> >  	enum iio_modifier modifier;
> >  	enum iio_chan_type type;
> >  	struct iio_dev *iiodev;
> > +	struct device *dev = &sdev->dev;
> > +	const struct scmi_handle *handle = sdev->handle;
> >  	int i, ret;
> >  
> >  	iiodev = devm_iio_device_alloc(dev, sizeof(*sensor));
> > @@ -560,7 +535,7 @@ static struct iio_dev *scmi_alloc_iiodev(struct device *dev,
> >  	iiodev->modes = INDIO_DIRECT_MODE;
> >  	iiodev->dev.parent = dev;
> >  	sensor = iio_priv(iiodev);
> > -	sensor->handle = handle;
> > +	sensor->ph = ph;
> >  	sensor->sensor_info = sensor_info;
> >  	sensor->sensor_update_nb.notifier_call = scmi_iio_sensor_update_cb;
> >  	sensor->indio_dev = iiodev;
> > @@ -595,6 +570,17 @@ static struct iio_dev *scmi_alloc_iiodev(struct device *dev,
> >  					  sensor_info->axis[i].id);
> >  	}
> >  
> > +	ret = handle->notify_ops->devm_event_notifier_register(sdev,
> > +				SCMI_PROTOCOL_SENSOR, SCMI_EVENT_SENSOR_UPDATE,
> > +				&sensor->sensor_info->id,
> > +				&sensor->sensor_update_nb);
> > +	if (ret) {
> > +		dev_err(&iiodev->dev,
> > +			"Error in registering sensor update notifier for sensor %s err %d",
> > +			sensor->sensor_info->name, ret);
> > +		return ERR_PTR(ret);
> > +	}
> > +
> >  	scmi_iio_set_timestamp_channel(&iio_channels[i], i);
> >  	iiodev->channels = iio_channels;
> >  	return iiodev;
> > @@ -604,24 +590,29 @@ static int scmi_iio_dev_probe(struct scmi_device *sdev)
> >  {
> >  	const struct scmi_sensor_info *sensor_info;
> >  	struct scmi_handle *handle = sdev->handle;
> > +	struct scmi_protocol_handle *ph;
> >  	struct device *dev = &sdev->dev;
> >  	struct iio_dev *scmi_iio_dev;
> >  	u16 nr_sensors;
> >  	int err = -ENODEV, i;
> >  
> > -	if (!handle || !handle->sensor_ops) {
> > +	if (!handle)
> > +		return -ENODEV;
> > +
> > +	sensor_ops = handle->devm_protocol_get(sdev, SCMI_PROTOCOL_SENSOR, &ph);
> > +	if (IS_ERR(sensor_ops)) {
> >  		dev_err(dev, "SCMI device has no sensor interface\n");
> > -		return -EINVAL;
> > +		return PTR_ERR(sensor_ops);
> >  	}
> >  
> > -	nr_sensors = handle->sensor_ops->count_get(handle);
> > +	nr_sensors = sensor_ops->count_get(ph);
> >  	if (!nr_sensors) {
> >  		dev_dbg(dev, "0 sensors found via SCMI bus\n");
> >  		return -ENODEV;
> >  	}
> >  
> >  	for (i = 0; i < nr_sensors; i++) {
> > -		sensor_info = handle->sensor_ops->info_get(handle, i);
> > +		sensor_info = sensor_ops->info_get(ph, i);
> >  		if (!sensor_info) {
> >  			dev_err(dev, "SCMI sensor %d has missing info\n", i);
> >  			return -EINVAL;
> > @@ -636,7 +627,7 @@ static int scmi_iio_dev_probe(struct scmi_device *sdev)
> >  		    sensor_info->axis[0].type != RADIANS_SEC)
> >  			continue;
> >  
> > -		scmi_iio_dev = scmi_alloc_iiodev(dev, handle, sensor_info);
> > +		scmi_iio_dev = scmi_alloc_iiodev(sdev, ph, sensor_info);
> >  		if (IS_ERR(scmi_iio_dev)) {
> >  			dev_err(dev,
> >  				"failed to allocate IIO device for sensor %s: %ld\n",
> 

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