drivers/iio/dummy/iio_simple_dummy_buffer.c

   1 /**
   2  * Copyright (c) 2011 Jonathan Cameron
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 as published by
   6  * the Free Software Foundation.
   7  *
   8  * Buffer handling elements of industrial I/O reference driver.
   9  * Uses the kfifo buffer.
  10  *
  11  * To test without hardware use the sysfs trigger.
  12  */
  13
  14 #include <linux/kernel.h>
  15 #include <linux/export.h>
  16 #include <linux/slab.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/irq.h>
  19 #include <linux/bitmap.h>
  20
  21 #include <linux/iio/iio.h>
  22 #include <linux/iio/trigger_consumer.h>
  23 #include <linux/iio/kfifo_buf.h>
  24
  25 #include "iio_simple_dummy.h"
  26
  27 /* Some fake data */
  28
  29 static const s16 fakedata[] = {
  30         [DUMMY_INDEX_VOLTAGE_0] = 7,
  31         [DUMMY_INDEX_DIFFVOLTAGE_1M2] = -33,
  32         [DUMMY_INDEX_DIFFVOLTAGE_3M4] = -2,
  33         [DUMMY_INDEX_ACCELX] = 344,
  34 };
  35
  36 /**
  37  * iio_simple_dummy_trigger_h() - the trigger handler function
  38  * @irq: the interrupt number
  39  * @p: private data - always a pointer to the poll func.
  40  *
  41  * This is the guts of buffered capture. On a trigger event occurring,
  42  * if the pollfunc is attached then this handler is called as a threaded
  43  * interrupt (and hence may sleep). It is responsible for grabbing data
  44  * from the device and pushing it into the associated buffer.
  45  */
  46 static irqreturn_t iio_simple_dummy_trigger_h(int irq, void *p)
  47 {
  48         struct iio_poll_func *pf = p;
  49         struct iio_dev *indio_dev = pf->indio_dev;
  50         int len = 0;
  51         u16 *data;
  52
  53         data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
  54         if (!data)
  55                 goto done;
  56
  57         if (!bitmap_empty(indio_dev->active_scan_mask, indio_dev->masklength)) {
  58                 /*
  59                  * Three common options here:
  60                  * hardware scans: certain combinations of channels make
  61                  *   up a fast read.  The capture will consist of all of them.
  62                  *   Hence we just call the grab data function and fill the
  63                  *   buffer without processing.
  64                  * software scans: can be considered to be random access
  65                  *   so efficient reading is just a case of minimal bus
  66                  *   transactions.
  67                  * software culled hardware scans:
  68                  *   occasionally a driver may process the nearest hardware
  69                  *   scan to avoid storing elements that are not desired. This
  70                  *   is the fiddliest option by far.
  71                  * Here let's pretend we have random access. And the values are
  72                  * in the constant table fakedata.
  73                  */
  74                 int i, j;
  75
  76                 for (i = 0, j = 0;
  77                      i < bitmap_weight(indio_dev->active_scan_mask,
  78                                        indio_dev->masklength);
  79                      i++, j++) {
  80                         j = find_next_bit(indio_dev->active_scan_mask,
  81                                           indio_dev->masklength, j);
  82                         /* random access read from the 'device' */
  83                         data[i] = fakedata[j];
  84                         len += 2;
  85                 }
  86         }
  87
  88         iio_push_to_buffers_with_timestamp(indio_dev, data,
  89                                            iio_get_time_ns(indio_dev));
  90
  91         kfree(data);
  92
  93 done:
  94         /*
  95          * Tell the core we are done with this trigger and ready for the
  96          * next one.
  97          */
  98         iio_trigger_notify_done(indio_dev->trig);
  99
 100         return IRQ_HANDLED;
 101 }
 102
 103 static const struct iio_buffer_setup_ops iio_simple_dummy_buffer_setup_ops = {
 104         /*
 105          * iio_triggered_buffer_postenable:
 106          * Generic function that simply attaches the pollfunc to the trigger.
 107          * Replace this to mess with hardware state before we attach the
 108          * trigger.
 109          */
 110         .postenable = &iio_triggered_buffer_postenable,
 111         /*
 112          * iio_triggered_buffer_predisable:
 113          * Generic function that simple detaches the pollfunc from the trigger.
 114          * Replace this to put hardware state back again after the trigger is
 115          * detached but before userspace knows we have disabled the ring.
 116          */
 117         .predisable = &iio_triggered_buffer_predisable,
 118 };
 119
 120 int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev)
 121 {
 122         int ret;
 123         struct iio_buffer *buffer;
 124
 125         /* Allocate a buffer to use - here a kfifo */
 126         buffer = iio_kfifo_allocate();
 127         if (!buffer) {
 128                 ret = -ENOMEM;
 129                 goto error_ret;
 130         }
 131
 132         iio_device_attach_buffer(indio_dev, buffer);
 133
 134         /* Enable timestamps by default */
 135         buffer->scan_timestamp = true;
 136
 137         /*
 138          * Tell the core what device type specific functions should
 139          * be run on either side of buffer capture enable / disable.
 140          */
 141         indio_dev->setup_ops = &iio_simple_dummy_buffer_setup_ops;
 142
 143         /*
 144          * Configure a polling function.
 145          * When a trigger event with this polling function connected
 146          * occurs, this function is run. Typically this grabs data
 147          * from the device.
 148          *
 149          * NULL for the bottom half. This is normally implemented only if we
 150          * either want to ping a capture now pin (no sleeping) or grab
 151          * a timestamp as close as possible to a data ready trigger firing.
 152          *
 153          * IRQF_ONESHOT ensures irqs are masked such that only one instance
 154          * of the handler can run at a time.
 155          *
 156          * "iio_simple_dummy_consumer%d" formatting string for the irq 'name'
 157          * as seen under /proc/interrupts. Remaining parameters as per printk.
 158          */
 159         indio_dev->pollfunc = iio_alloc_pollfunc(NULL,
 160                                                  &iio_simple_dummy_trigger_h,
 161                                                  IRQF_ONESHOT,
 162                                                  indio_dev,
 163                                                  "iio_simple_dummy_consumer%d",
 164                                                  indio_dev->id);
 165
 166         if (!indio_dev->pollfunc) {
 167                 ret = -ENOMEM;
 168                 goto error_free_buffer;
 169         }
 170
 171         /*
 172          * Notify the core that this device is capable of buffered capture
 173          * driven by a trigger.
 174          */
 175         indio_dev->modes |= INDIO_BUFFER_TRIGGERED;
 176
 177         return 0;
 178
 179 error_free_buffer:
 180         iio_kfifo_free(indio_dev->buffer);
 181 error_ret:
 182         return ret;
 183 }
 184
 185 /**
 186  * iio_simple_dummy_unconfigure_buffer() - release buffer resources
 187  * @indo_dev: device instance state
 188  */
 189 void iio_simple_dummy_unconfigure_buffer(struct iio_dev *indio_dev)
 190 {
 191         iio_dealloc_pollfunc(indio_dev->pollfunc);
 192         iio_kfifo_free(indio_dev->buffer);
 193 }