drivers/iio/dummy/iio_simple_dummy_buffer.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (c) 2011 Jonathan Cameron
   4  *
   5  * Buffer handling elements of industrial I/O reference driver.
   6  * Uses the kfifo buffer.
   7  *
   8  * To test without hardware use the sysfs trigger.
   9  */
  10
  11 #include <linux/kernel.h>
  12 #include <linux/export.h>
  13 #include <linux/slab.h>
  14 #include <linux/interrupt.h>
  15 #include <linux/irq.h>
  16 #include <linux/bitmap.h>
  17
  18 #include <linux/iio/iio.h>
  19 #include <linux/iio/trigger_consumer.h>
  20 #include <linux/iio/buffer.h>
  21 #include <linux/iio/kfifo_buf.h>
  22
  23 #include "iio_simple_dummy.h"
  24
  25 /* Some fake data */
  26
  27 static const s16 fakedata[] = {
  28         [DUMMY_INDEX_VOLTAGE_0] = 7,
  29         [DUMMY_INDEX_DIFFVOLTAGE_1M2] = -33,
  30         [DUMMY_INDEX_DIFFVOLTAGE_3M4] = -2,
  31         [DUMMY_INDEX_ACCELX] = 344,
  32 };
  33
  34 /**
  35  * iio_simple_dummy_trigger_h() - the trigger handler function
  36  * @irq: the interrupt number
  37  * @p: private data - always a pointer to the poll func.
  38  *
  39  * This is the guts of buffered capture. On a trigger event occurring,
  40  * if the pollfunc is attached then this handler is called as a threaded
  41  * interrupt (and hence may sleep). It is responsible for grabbing data
  42  * from the device and pushing it into the associated buffer.
  43  */
  44 static irqreturn_t iio_simple_dummy_trigger_h(int irq, void *p)
  45 {
  46         struct iio_poll_func *pf = p;
  47         struct iio_dev *indio_dev = pf->indio_dev;
  48         int len = 0;
  49         u16 *data;
  50
  51         data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
  52         if (!data)
  53                 goto done;
  54
  55         if (!bitmap_empty(indio_dev->active_scan_mask, indio_dev->masklength)) {
  56                 /*
  57                  * Three common options here:
  58                  * hardware scans: certain combinations of channels make
  59                  *   up a fast read.  The capture will consist of all of them.
  60                  *   Hence we just call the grab data function and fill the
  61                  *   buffer without processing.
  62                  * software scans: can be considered to be random access
  63                  *   so efficient reading is just a case of minimal bus
  64                  *   transactions.
  65                  * software culled hardware scans:
  66                  *   occasionally a driver may process the nearest hardware
  67                  *   scan to avoid storing elements that are not desired. This
  68                  *   is the fiddliest option by far.
  69                  * Here let's pretend we have random access. And the values are
  70                  * in the constant table fakedata.
  71                  */
  72                 int i, j;
  73
  74                 for (i = 0, j = 0;
  75                      i < bitmap_weight(indio_dev->active_scan_mask,
  76                                        indio_dev->masklength);
  77                      i++, j++) {
  78                         j = find_next_bit(indio_dev->active_scan_mask,
  79                                           indio_dev->masklength, j);
  80                         /* random access read from the 'device' */
  81                         data[i] = fakedata[j];
  82                         len += 2;
  83                 }
  84         }
  85
  86         iio_push_to_buffers_with_timestamp(indio_dev, data,
  87                                            iio_get_time_ns(indio_dev));
  88
  89         kfree(data);
  90
  91 done:
  92         /*
  93          * Tell the core we are done with this trigger and ready for the
  94          * next one.
  95          */
  96         iio_trigger_notify_done(indio_dev->trig);
  97
  98         return IRQ_HANDLED;
  99 }
 100
 101 static const struct iio_buffer_setup_ops iio_simple_dummy_buffer_setup_ops = {
 102 };
 103
 104 int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev)
 105 {
 106         int ret;
 107         struct iio_buffer *buffer;
 108
 109         /* Allocate a buffer to use - here a kfifo */
 110         buffer = iio_kfifo_allocate();
 111         if (!buffer) {
 112                 ret = -ENOMEM;
 113                 goto error_ret;
 114         }
 115
 116         iio_device_attach_buffer(indio_dev, buffer);
 117
 118         /*
 119          * Tell the core what device type specific functions should
 120          * be run on either side of buffer capture enable / disable.
 121          */
 122         indio_dev->setup_ops = &iio_simple_dummy_buffer_setup_ops;
 123
 124         /*
 125          * Configure a polling function.
 126          * When a trigger event with this polling function connected
 127          * occurs, this function is run. Typically this grabs data
 128          * from the device.
 129          *
 130          * NULL for the bottom half. This is normally implemented only if we
 131          * either want to ping a capture now pin (no sleeping) or grab
 132          * a timestamp as close as possible to a data ready trigger firing.
 133          *
 134          * IRQF_ONESHOT ensures irqs are masked such that only one instance
 135          * of the handler can run at a time.
 136          *
 137          * "iio_simple_dummy_consumer%d" formatting string for the irq 'name'
 138          * as seen under /proc/interrupts. Remaining parameters as per printk.
 139          */
 140         indio_dev->pollfunc = iio_alloc_pollfunc(NULL,
 141                                                  &iio_simple_dummy_trigger_h,
 142                                                  IRQF_ONESHOT,
 143                                                  indio_dev,
 144                                                  "iio_simple_dummy_consumer%d",
 145                                                  indio_dev->id);
 146
 147         if (!indio_dev->pollfunc) {
 148                 ret = -ENOMEM;
 149                 goto error_free_buffer;
 150         }
 151
 152         /*
 153          * Notify the core that this device is capable of buffered capture
 154          * driven by a trigger.
 155          */
 156         indio_dev->modes |= INDIO_BUFFER_TRIGGERED;
 157
 158         return 0;
 159
 160 error_free_buffer:
 161         iio_kfifo_free(indio_dev->buffer);
 162 error_ret:
 163         return ret;
 164 }
 165
 166 /**
 167  * iio_simple_dummy_unconfigure_buffer() - release buffer resources
 168  * @indio_dev: device instance state
 169  */
 170 void iio_simple_dummy_unconfigure_buffer(struct iio_dev *indio_dev)
 171 {
 172         iio_dealloc_pollfunc(indio_dev->pollfunc);
 173         iio_kfifo_free(indio_dev->buffer);
 174 }