drivers/staging/iio/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 "iio.h"
  22 #include "trigger_consumer.h"
  23 #include "kfifo_buf.h"
  24
  25 #include "iio_simple_dummy.h"
  26
  27 /* Some fake data */
  28
  29 static const s16 fakedata[] = {
  30         [voltage0] = 7,
  31         [diffvoltage1m2] = -33,
  32         [diffvoltage3m4] = -2,
  33         [accelx] = 344,
  34 };
  35 /**
  36  * iio_simple_dummy_trigger_h() - the trigger handler function
  37  * @irq: the interrupt number
  38  * @p: private data - always a pointer to the poll func.
  39  *
  40  * This is the guts of buffered capture. On a trigger event occuring,
  41  * if the pollfunc is attached then this handler is called as a threaded
  42  * interrupt (and hence may sleep). It is responsible for grabbing data
  43  * from the device and pushing it into the associated buffer.
  44  */
  45 static irqreturn_t iio_simple_dummy_trigger_h(int irq, void *p)
  46 {
  47         struct iio_poll_func *pf = p;
  48         struct iio_dev *indio_dev = pf->indio_dev;
  49         struct iio_buffer *buffer = indio_dev->buffer;
  50         int len = 0;
  51         /*
  52          * The datasize is obtained from the buffer. It was stored when
  53          * the preenable setup function was called.
  54          */
  55         size_t datasize = buffer->access->get_bytes_per_datum(buffer);
  56         u16 *data = kmalloc(datasize, GFP_KERNEL);
  57         if (data == NULL)
  58                 return -ENOMEM;
  59
  60         if (buffer->scan_count) {
  61                 /*
  62                  * Three common options here:
  63                  * hardware scans: certain combinations of channels make
  64                  *   up a fast read.  The capture will consist of all of them.
  65                  *   Hence we just call the grab data function and fill the
  66                  *   buffer without processing.
  67                  * sofware scans: can be considered to be random access
  68                  *   so efficient reading is just a case of minimal bus
  69                  *   transactions.
  70                  * software culled hardware scans:
  71                  *   occasionally a driver may process the nearest hardware
  72                  *   scan to avoid storing elements that are not desired. This
  73                  *   is the fidliest option by far.
  74                  * Here lets pretend we have random access. And the values are
  75                  * in the constant table fakedata.
  76                  */
  77                 int i, j;
  78                 for (i = 0, j = 0; i < buffer->scan_count; i++) {
  79                         j = find_next_bit(buffer->scan_mask,
  80                                           indio_dev->masklength, j + 1);
  81                         /* random access read form the 'device' */
  82                         data[i] = fakedata[j];
  83                         len += 2;
  84                 }
  85         }
  86         /* Store a timestampe at an 8 byte boundary */
  87         if (buffer->scan_timestamp)
  88                 *(s64 *)(((phys_addr_t)data + len
  89                                 + sizeof(s64) - 1) & ~(sizeof(s64) - 1))
  90                         = iio_get_time_ns();
  91         buffer->access->store_to(buffer, (u8 *)data, pf->timestamp);
  92
  93         kfree(data);
  94
  95         /*
  96          * Tell the core we are done with this trigger and ready for the
  97          * next one.
  98          */
  99         iio_trigger_notify_done(indio_dev->trig);
 100
 101         return IRQ_HANDLED;
 102 }
 103
 104 static const struct iio_buffer_setup_ops iio_simple_dummy_buffer_setup_ops = {
 105         /*
 106          * iio_sw_buffer_preenable:
 107          * Generic function for equal sized ring elements + 64 bit timestamp
 108          * Assumes that any combination of channels can be enabled.
 109          * Typically replaced to implement restrictions on what combinations
 110          * can be captured (hardware scan modes).
 111          */
 112         .preenable = &iio_sw_buffer_preenable,
 113         /*
 114          * iio_triggered_buffer_postenable:
 115          * Generic function that simply attaches the pollfunc to the trigger.
 116          * Replace this to mess with hardware state before we attach the
 117          * trigger.
 118          */
 119         .postenable = &iio_triggered_buffer_postenable,
 120         /*
 121          * iio_triggered_buffer_predisable:
 122          * Generic function that simple detaches the pollfunc from the trigger.
 123          * Replace this to put hardware state back again after the trigger is
 124          * detached but before userspace knows we have disabled the ring.
 125          */
 126         .predisable = &iio_triggered_buffer_predisable,
 127 };
 128
 129 int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev)
 130 {
 131         int ret;
 132         struct iio_buffer *buffer;
 133
 134         /* Allocate a buffer to use - here a kfifo */
 135         buffer = iio_kfifo_allocate(indio_dev);
 136         if (buffer == NULL) {
 137                 ret = -ENOMEM;
 138                 goto error_ret;
 139         }
 140
 141         indio_dev->buffer = buffer;
 142         /* Tell the core how to access the buffer */
 143         buffer->access = &kfifo_access_funcs;
 144
 145         /* Number of bytes per element */
 146         buffer->bpe = 2;
 147         /* Enable timestamps by default */
 148         buffer->scan_timestamp = true;
 149
 150         /*
 151          * Tell the core what device type specific functions should
 152          * be run on either side of buffer capture enable / disable.
 153          */
 154         buffer->setup_ops = &iio_simple_dummy_buffer_setup_ops;
 155         buffer->owner = THIS_MODULE;
 156
 157         /*
 158          * Configure a polling function.
 159          * When a trigger event with this polling function connected
 160          * occurs, this function is run. Typically this grabs data
 161          * from the device.
 162          *
 163          * NULL for the top half. This is normally implemented only if we
 164          * either want to ping a capture now pin (no sleeping) or grab
 165          * a timestamp as close as possible to a data ready trigger firing.
 166          *
 167          * IRQF_ONESHOT ensures irqs are masked such that only one instance
 168          * of the handler can run at a time.
 169          *
 170          * "iio_simple_dummy_consumer%d" formatting string for the irq 'name'
 171          * as seen under /proc/interrupts. Remaining parameters as per printk.
 172          */
 173         indio_dev->pollfunc = iio_alloc_pollfunc(NULL,
 174                                                  &iio_simple_dummy_trigger_h,
 175                                                  IRQF_ONESHOT,
 176                                                  indio_dev,
 177                                                  "iio_simple_dummy_consumer%d",
 178                                                  indio_dev->id);
 179
 180         if (indio_dev->pollfunc == NULL) {
 181                 ret = -ENOMEM;
 182                 goto error_free_buffer;
 183         }
 184
 185         /*
 186          * Notify the core that this device is capable of buffered capture
 187          * driven by a trigger.
 188          */
 189         indio_dev->modes |= INDIO_BUFFER_TRIGGERED;
 190         return 0;
 191
 192 error_free_buffer:
 193         iio_kfifo_free(indio_dev->buffer);
 194 error_ret:
 195         return ret;
 196
 197 }
 198
 199 /**
 200  * iio_simple_dummy_unconfigure_buffer() - release buffer resources
 201  * @indo_dev: device instance state
 202  */
 203 void iio_simple_dummy_unconfigure_buffer(struct iio_dev *indio_dev)
 204 {
 205         iio_dealloc_pollfunc(indio_dev->pollfunc);
 206         iio_kfifo_free(indio_dev->buffer);
 207 }