text: /*
   * AD7298 SPI ADC driver
   *
   * Copyright 2011 Analog Devices Inc.
   *
   * Licensed under the GPL-2.
   */
  
  #include <linux/interrupt.h>
  #include <linux/kernel.h>
  #include <linux/slab.h>
  #include <linux/spi/spi.h>
  
  #include "../iio.h"
  #include "../buffer.h"
  #include "../ring_sw.h"
  #include "../trigger_consumer.h"
  
  #include "ad7298.h"
  
  /**
   * ad7298_ring_preenable() setup the parameters of the ring before enabling
   *
   * The complex nature of the setting of the number of bytes per datum is due
   * to this driver currently ensuring that the timestamp is stored at an 8
   * byte boundary.
   **/
  static int ad7298_ring_preenable(struct iio_dev *indio_dev)
  {
  	struct ad7298_state *st = iio_priv(indio_dev);
  	struct iio_buffer *ring = indio_dev->buffer;
  	size_t d_size;
  	int i, m;
  	unsigned short command;
  	int scan_count = bitmap_weight(indio_dev->active_scan_mask,
  				       indio_dev->masklength);
  	d_size = scan_count * (AD7298_STORAGE_BITS / 8);
  
  	if (ring->scan_timestamp) {
  		d_size += sizeof(s64);
  
  		if (d_size % sizeof(s64))
  			d_size += sizeof(s64) - (d_size % sizeof(s64));
  	}
  
  	if (ring->access->set_bytes_per_datum)
  		ring->access->set_bytes_per_datum(ring, d_size);
  
  	st->d_size = d_size;
  
  	command = AD7298_WRITE | st->ext_ref;
  
  	for (i = 0, m = AD7298_CH(0); i < AD7298_MAX_CHAN; i++, m >>= 1)
  		if (test_bit(i, indio_dev->active_scan_mask))
  			command |= m;
  
  	st->tx_buf[0] = cpu_to_be16(command);
  
  	/* build spi ring message */
  	st->ring_xfer[0].tx_buf = &st->tx_buf[0];
  	st->ring_xfer[0].len = 2;
  	st->ring_xfer[0].cs_change = 1;
  	st->ring_xfer[1].tx_buf = &st->tx_buf[1];
  	st->ring_xfer[1].len = 2;
  	st->ring_xfer[1].cs_change = 1;
  
  	spi_message_init(&st->ring_msg);
  	spi_message_add_tail(&st->ring_xfer[0], &st->ring_msg);
  	spi_message_add_tail(&st->ring_xfer[1], &st->ring_msg);
  
  	for (i = 0; i < scan_count; i++) {
  		st->ring_xfer[i + 2].rx_buf = &st->rx_buf[i];
  		st->ring_xfer[i + 2].len = 2;
  		st->ring_xfer[i + 2].cs_change = 1;
  		spi_message_add_tail(&st->ring_xfer[i + 2], &st->ring_msg);
  	}
  	/* make sure last transfer cs_change is not set */
  	st->ring_xfer[i + 1].cs_change = 0;
  
  	return 0;
  }
  
  /**
   * ad7298_trigger_handler() bh of trigger launched polling to ring buffer
   *
   * Currently there is no option in this driver to disable the saving of
   * timestamps within the ring.
   **/
  static irqreturn_t ad7298_trigger_handler(int irq, void *p)
  {
  	struct iio_poll_func *pf = p;
  	struct iio_dev *indio_dev = pf->indio_dev;
  	struct ad7298_state *st = iio_priv(indio_dev);
  	struct iio_buffer *ring = indio_dev->buffer;
  	s64 time_ns;
  	__u16 buf[16];
  	int b_sent, i;
  
  	b_sent = spi_sync(st->spi, &st->ring_msg);
  	if (b_sent)
  		return b_sent;
  
  	if (ring->scan_timestamp) {
  		time_ns = iio_get_time_ns();
  		memcpy((u8 *)buf + st->d_size - sizeof(s64),
  			&time_ns, sizeof(time_ns));
  	}
  
  	for (i = 0; i < bitmap_weight(indio_dev->active_scan_mask,
  						 indio_dev->masklength); i++)
  		buf[i] = be16_to_cpu(st->rx_buf[i]);
  
  	indio_dev->buffer->access->store_to(ring, (u8 *)buf, time_ns);
  	iio_trigger_notify_done(indio_dev->trig);
  
  	return IRQ_HANDLED;
  }
  
  static const struct iio_buffer_setup_ops ad7298_ring_setup_ops = {
  	.preenable = &ad7298_ring_preenable,
  	.postenable = &iio_triggered_buffer_postenable,
  	.predisable = &iio_triggered_buffer_predisable,
  };
  
  int ad7298_register_ring_funcs_and_init(struct iio_dev *indio_dev)
  {
  	int ret;
  
  	indio_dev->buffer = iio_sw_rb_allocate(indio_dev);
  	if (!indio_dev->buffer) {
  		ret = -ENOMEM;
  		goto error_ret;
  	}
  	/* Effectively select the ring buffer implementation */
  	indio_dev->buffer->access = &ring_sw_access_funcs;
  
  	indio_dev->pollfunc = iio_alloc_pollfunc(NULL,
  						 &ad7298_trigger_handler,
  						 IRQF_ONESHOT,
  						 indio_dev,
  						 "ad7298_consumer%d",
  						 indio_dev->id);
  
  	if (indio_dev->pollfunc == NULL) {
  		ret = -ENOMEM;
  		goto error_deallocate_sw_rb;
  	}
  
  	/* Ring buffer functions - here trigger setup related */
  	indio_dev->setup_ops = &ad7298_ring_setup_ops;
  	indio_dev->buffer->scan_timestamp = true;
  
  	/* Flag that polled ring buffering is possible */
  	indio_dev->modes |= INDIO_BUFFER_TRIGGERED;
  	return 0;
  
  error_deallocate_sw_rb:
  	iio_sw_rb_free(indio_dev->buffer);
  error_ret:
  	return ret;
  }
  
  void ad7298_ring_cleanup(struct iio_dev *indio_dev)
  {
  	iio_dealloc_pollfunc(indio_dev->pollfunc);
  	iio_sw_rb_free(indio_dev->buffer);
  }
  