Re: [PATCH v2 2/2] ti-adc081c: Initial triggered buffer support

Jonathan Cameron
2016-04-10T14:29:14Z

On 04/04/16 19:21, Crestez Dan Leonard wrote:
> Using this requires software triggers like CONFIG_IIO_HRTIMER_TRIGGER.
>
> The device can be configured to do internal periodic sampling but does not
> offer some sort of interrupt on data ready. Interrupts can only trigger when
> values get out of a specific range.
>
> Signed-off-by: Crestez Dan Leonard <leonard.crestez@intel.com>
basically fine, but just use a fixed size allocation for your buffer in the
trigger handler.
> ---
> drivers/iio/adc/ti-adc081c.c | 63 +++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 54 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/iio/adc/ti-adc081c.c b/drivers/iio/adc/ti-adc081c.c
> index 3b3c656..d024df2 100644
> --- a/drivers/iio/adc/ti-adc081c.c
> +++ b/drivers/iio/adc/ti-adc081c.c
> @@ -24,6 +24,9 @@
> #include <linux/of.h>
>
> #include <linux/iio/iio.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
> #include <linux/regulator/consumer.h>
>
> struct adc081c {
> @@ -69,18 +72,31 @@ static int adc081c_read_raw(struct iio_dev *iio,
> return -EINVAL;
> }
>
> -static const struct iio_chan_spec adc081c_channel = {
> - .type = IIO_VOLTAGE,
> - .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
> - .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
> -};
> +#define ADCxx1C_CHAN(_bits) { \
> + .type = IIO_VOLTAGE, \
> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> + .scan_type = { \
> + .sign = 'u', \
> + .realbits = (_bits), \
> + .storagebits = 16, \
> + .shift = 12 - (_bits), \
> + .endianness = IIO_CPU, \
> + }, \
> +}
>
> struct adcxx1c_model {
> + const struct iio_chan_spec* channels;
> int bits;
> };
>
> #define DEFINE_ADCxx1C_MODEL(_name, _bits) \
> + static const struct iio_chan_spec _name ## _channels[] = { \
> + ADCxx1C_CHAN((_bits)), \
> + IIO_CHAN_SOFT_TIMESTAMP(1), \
> + }; \
> static const struct adcxx1c_model _name ## _model = { \
> + .channels = _name ## _channels, \
> .bits = (_bits), \
> }
>
> @@ -88,11 +104,31 @@ DEFINE_ADCxx1C_MODEL(adc081c, 8);
> DEFINE_ADCxx1C_MODEL(adc101c, 10);
> DEFINE_ADCxx1C_MODEL(adc121c, 12);
>
> +#define ADC081C_NUM_CHANNELS 2
> +
> static const struct iio_info adc081c_info = {
> .read_raw = adc081c_read_raw,
> .driver_module = THIS_MODULE,
> };
>
> +static irqreturn_t adc081c_trigger_handler(int irq, void *p)
> +{
> + struct iio_poll_func *pf = p;
> + struct iio_dev *indio_dev = pf->indio_dev;
> + struct adc081c *data = iio_priv(indio_dev);
> + u16 buf[indio_dev->scan_bytes / 2];
Just use a fixed size that is beig enough for whatever you may
get. Here you need room for a word + an aligned 8 byte timestamp
so 16 bytes, or 8 u16s. It's not variable so don't let the compiler think
it is.

Also you shouldn't be accessing indio_dev->scan_bytes directly in a driver.
A long time back we spent a while pulling that idiom out of drivers as it
was causing a lot more trouble than the convenience was worth (can't
actually recall why now though!)
> + int ret;
> +
> + ret = i2c_smbus_read_word_swapped(data->i2c, REG_CONV_RES);
> + if (ret < 0)
> + goto out;
> + buf[0] = ret;
> + iio_push_to_buffers_with_timestamp(indio_dev, buf, iio_get_time_ns());
> +out:
> + iio_trigger_notify_done(indio_dev->trig);
> + return IRQ_HANDLED;
> +}
> +
> static int adc081c_probe(struct i2c_client *client,
> const struct i2c_device_id *id)
> {
> @@ -125,18 +161,26 @@ static int adc081c_probe(struct i2c_client *client,
> iio->modes = INDIO_DIRECT_MODE;
> iio->info = &adc081c_info;
>
> - iio->channels = &adc081c_channel;
> - iio->num_channels = 1;
> + iio->channels = model->channels;
> + iio->num_channels = ADC081C_NUM_CHANNELS;
I'm not sure the define adds anything here! Kind of obvious what 2 means anyway -
rather than it being a magic number :)
> +
> + err = iio_triggered_buffer_setup(iio, NULL, adc081c_trigger_handler, NULL);
> + if (err < 0) {
> + dev_err(&client->dev, "iio triggered buffer setup failed\n");
> + goto err_regulator_disable;
> + }
>
> err = iio_device_register(iio);
> if (err < 0)
> - goto regulator_disable;
> + goto err_buffer_cleanup;
>
> i2c_set_clientdata(client, iio);
>
> return 0;
>
> -regulator_disable:
> +err_buffer_cleanup:
> + iio_triggered_buffer_cleanup(iio);
> +err_regulator_disable:
> regulator_disable(adc->ref);
>
> return err;
> @@ -148,6 +192,7 @@ static int adc081c_remove(struct i2c_client *client)
> struct adc081c *adc = iio_priv(iio);
>
> iio_device_unregister(iio);
> + iio_triggered_buffer_cleanup(iio);
> regulator_disable(adc->ref);
>
> return 0;
>