Re: [PATCH V4 7/7] iio: mma8452: Add support for interrupt driven triggers.

[Jonathan Cameron <jic23@kernel.org>]

On 13/05/15 11:26, Martin Fuzzey wrote:
> Implement interrupt driven trigger for data ready.
> This allows more efficient access to the sample data.
> 
> Signed-off-by: Martin Fuzzey <mfuzzey@parkeon.com>
> ---
>  drivers/iio/accel/mma8452.c |   85 ++++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 79 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c
> index 5f2977f..e568d34 100644
> --- a/drivers/iio/accel/mma8452.c
> +++ b/drivers/iio/accel/mma8452.c
> @@ -18,6 +18,8 @@
>  #include <linux/iio/sysfs.h>
>  #include <linux/iio/trigger_consumer.h>
>  #include <linux/iio/buffer.h>
> +#include <linux/iio/trigger.h>
> +#include <linux/iio/trigger_consumer.h>
>  #include <linux/iio/triggered_buffer.h>
>  #include <linux/iio/events.h>
>  #include <linux/delay.h>
> @@ -66,6 +68,7 @@
>  #define MMA8452_DATA_CFG_FS_8G 2
>  #define MMA8452_DATA_CFG_HPF_MASK BIT(4)
>  
> +#define MMA8452_INT_DRDY	BIT(0)
>  #define MMA8452_INT_TRANS	BIT(5)
>  
>  #define MMA8452_DEVICE_ID 0x2a
> @@ -577,18 +580,24 @@ static irqreturn_t mma8452_interrupt(int irq, void *p)
>  {
>  	struct iio_dev *indio_dev = p;
>  	struct mma8452_data *data = iio_priv(indio_dev);
> +	int ret = IRQ_NONE;
>  	int src;
>  
>  	src = i2c_smbus_read_byte_data(data->client, MMA8452_INT_SRC);
>  	if (src < 0)
>  		return IRQ_NONE;
>  
> +	if (src & MMA8452_INT_DRDY) {
> +		iio_trigger_poll_chained(indio_dev->trig);
Hmm. The issue with trigger_poll_chained is that it heavily restricts
the uses that can be made of the trigger by other devices. The top
half handler is never actually called as a result.

Given the whole point of the triggers stuff is to allow generic
use of triggers where possible, we need to ensure that if a device
is allowed to use a trigger, it always looks like a direct interrupt.

Two options for how to prevent odd things happening as a result:
1) Add a validate device callback to the trigger - that will prevent
it from being used for any other device.
2) irq_work_queues - see drivers/iio/light/gp2ap020a00f.c or the
sysfs trigger for how to do this.

> +		ret = IRQ_HANDLED;
> +	}
> +
>  	if (src & MMA8452_INT_TRANS) {
>  		mma8452_transient_interrupt(indio_dev);
> -		return IRQ_HANDLED;
> +		ret = IRQ_HANDLED;
>  	}
>  
> -	return IRQ_NONE;
> +	return ret;
>  }
>  
>  static irqreturn_t mma8452_trigger_handler(int irq, void *p)
> @@ -714,6 +723,60 @@ static const struct iio_info mma8452_info = {
>  
>  static const unsigned long mma8452_scan_masks[] = {0x7, 0};
>  
> +static int mma8452_data_rdy_trigger_set_state(struct iio_trigger *trig,
> +					      bool state)
> +{
> +	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
> +	struct mma8452_data *data = iio_priv(indio_dev);
> +	int reg;
> +
> +	reg = i2c_smbus_read_byte_data(data->client, MMA8452_CTRL_REG4);
> +	if (reg < 0)
> +		return reg;
> +
> +	if (state)
> +		reg |= MMA8452_INT_DRDY;
> +	else
> +		reg &= ~MMA8452_INT_DRDY;
> +
> +	return mma8452_change_config(data, MMA8452_CTRL_REG4, reg);
> +}
> +
> +static const struct iio_trigger_ops mma8452_trigger_ops = {
> +	.set_trigger_state = mma8452_data_rdy_trigger_set_state,
> +	.owner = THIS_MODULE,
> +};
> +
> +static int mma8452_trigger_setup(struct iio_dev *indio_dev)
> +{
> +	struct mma8452_data *data = iio_priv(indio_dev);
> +	struct iio_trigger *trig;
> +	int ret;
> +
> +	trig = devm_iio_trigger_alloc(&data->client->dev, "%s-dev%d",
> +				      indio_dev->name,
> +				      indio_dev->id);
> +	if (!trig)
> +		return -ENOMEM;
> +
> +	trig->dev.parent = &data->client->dev;
> +	trig->ops = &mma8452_trigger_ops;
> +	iio_trigger_set_drvdata(trig, indio_dev);
> +
> +	ret = iio_trigger_register(trig);
> +	if (ret)
> +		return ret;
> +
> +	indio_dev->trig = trig;
> +	return 0;
> +}
> +
> +static void mma8452_trigger_cleanup(struct iio_dev *indio_dev)
> +{
> +	if (indio_dev->trig)
> +		iio_trigger_unregister(indio_dev->trig);
> +}
> +
>  static int mma8452_reset(struct i2c_client *client)
>  {
>  	int i;
> @@ -794,7 +857,8 @@ static int mma8452_probe(struct i2c_client *client,
>  		 * enabled until userspace asks for it by
>  		 * mma8452_write_event_config()
>  		 */
> -		int supported_interrupts = MMA8452_INT_TRANS;
> +		int supported_interrupts = MMA8452_INT_DRDY | MMA8452_INT_TRANS;
> +		int enabled_interrupts = MMA8452_INT_TRANS;
>  
>  		/* Assume wired to INT1 pin */
>  		ret = i2c_smbus_write_byte_data(client,
> @@ -805,7 +869,11 @@ static int mma8452_probe(struct i2c_client *client,
>  
>  		ret = i2c_smbus_write_byte_data(client,
>  						MMA8452_CTRL_REG4,
> -						supported_interrupts);
> +						enabled_interrupts);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = mma8452_trigger_setup(indio_dev);
>  		if (ret < 0)
>  			return ret;
>  	}
> @@ -815,12 +883,12 @@ static int mma8452_probe(struct i2c_client *client,
>  	ret = i2c_smbus_write_byte_data(client, MMA8452_CTRL_REG1,
>  					data->ctrl_reg1);
>  	if (ret < 0)
> -		return ret;
> +		goto trigger_cleanup;
>  
>  	ret = iio_triggered_buffer_setup(indio_dev, NULL,
>  		mma8452_trigger_handler, NULL);
>  	if (ret < 0)
> -		return ret;
> +		goto trigger_cleanup;
>  
>  	if (client->irq) {
>  		ret = devm_request_threaded_irq(&client->dev,
> @@ -840,6 +908,10 @@ static int mma8452_probe(struct i2c_client *client,
>  
>  buffer_cleanup:
>  	iio_triggered_buffer_cleanup(indio_dev);
> +
> +trigger_cleanup:
> +	mma8452_trigger_cleanup(indio_dev);
> +
>  	return ret;
>  }
>  
> @@ -849,6 +921,7 @@ static int mma8452_remove(struct i2c_client *client)
>  
>  	iio_device_unregister(indio_dev);
>  	iio_triggered_buffer_cleanup(indio_dev);
> +	mma8452_trigger_cleanup(indio_dev);
>  	mma8452_standby(iio_priv(indio_dev));
>  
>  	return 0;
>