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/slab.h>
  16 #include <linux/interrupt.h>
  17 #include <linux/irq.h>
  18 #include <linux/bitmap.h>
  19
  20 #include "iio.h"
  21 #include "trigger_consumer.h"
  22 #include "kfifo_buf.h"
  23
  24 #include "iio_simple_dummy.h"
  25
  26 /* Some fake data */
  27
  28 static const s16 fakedata[] = {
  29         [voltage0] = 7,
  30         [diffvoltage1m2] = -33,
  31         [diffvoltage3m4] = -2,
  32         [accelx] = 344,
  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 occuring,
  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         struct iio_buffer *buffer = indio_dev->buffer;
  49         int len = 0;
  50         /*
  51          * The datasize is obtained from the buffer. It was stored when
  52          * the preenable setup function was called.
  53          */
  54         size_t datasize = buffer->access->get_bytes_per_datum(buffer);
  55         u16 *data = kmalloc(datasize, GFP_KERNEL);
  56         if (data == NULL)
  57                 return -ENOMEM;
  58
  59         if (buffer->scan_count) {
  60                 /*
  61                  * Three common options here:
  62                  * hardware scans: certain combinations of channels make
  63                  *   up a fast read.  The capture will consist of all of them.
  64                  *   Hence we just call the grab data function and fill the
  65                  *   buffer without processing.
  66                  * sofware scans: can be considered to be random access
  67                  *   so efficient reading is just a case of minimal bus
  68                  *   transactions.
  69                  * software culled hardware scans:
  70                  *   occasionally a driver may process the nearest hardware
  71                  *   scan to avoid storing elements that are not desired. This
  72                  *   is the fidliest option by far.
  73                  * Here lets pretend we have random access. And the values are
  74                  * in the constant table fakedata.
  75                  */
  76                 int i, j;
  77                 for (i = 0, j = 0; i < buffer->scan_count; i++) {
  78                         j = find_next_bit(buffer->scan_mask,
  79                                           indio_dev->masklength, j + 1);
  80                         /* random access read form the 'device' */
  81                         data[i] = fakedata[j];
  82                         len += 2;
  83                 }
  84         }
  85         /* Store a timestampe at an 8 byte boundary */
  86         if (buffer->scan_timestamp)
  87                 *(s64 *)(((phys_addr_t)data + len
  88                                 + sizeof(s64) - 1) & ~(sizeof(s64) - 1))
  89                         = iio_get_time_ns();
  90         buffer->access->store_to(buffer, (u8 *)data, pf->timestamp);
  91
  92         kfree(data);
  93
  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_sw_buffer_preenable:
 106          * Generic function for equal sized ring elements + 64 bit timestamp
 107          * Assumes that any combination of channels can be enabled.
 108          * Typically replaced to implement restrictions on what combinations
 109          * can be captured (hardware scan modes).
 110          */
 111         .preenable = &iio_sw_buffer_preenable,
 112         /*
 113          * iio_triggered_buffer_postenable:
 114          * Generic function that simply attaches the pollfunc to the trigger.
 115          * Replace this to mess with hardware state before we attach the
 116          * trigger.
 117          */
 118         .postenable = &iio_triggered_buffer_postenable,
 119         /*
 120          * iio_triggered_buffer_predisable:
 121          * Generic function that simple detaches the pollfunc from the trigger.
 122          * Replace this to put hardware state back again after the trigger is
 123          * detached but before userspace knows we have disabled the ring.
 124          */
 125         .predisable = &iio_triggered_buffer_predisable,
 126 };
 127
 128 int iio_simple_dummy_configure_buffer(struct iio_dev *indio_dev)
 129 {
 130         int ret;
 131         struct iio_buffer *buffer;
 132
 133         /* Allocate a buffer to use - here a kfifo */
 134         buffer = iio_kfifo_allocate(indio_dev);
 135         if (buffer == NULL) {
 136                 ret = -ENOMEM;
 137                 goto error_ret;
 138         }
 139
 140         indio_dev->buffer = buffer;
 141         /* Tell the core how to access the buffer */
 142         buffer->access = &kfifo_access_funcs;
 143
 144         /* Number of bytes per element */
 145         buffer->bpe = 2;
 146         /* Enable timestamps by default */
 147         buffer->scan_timestamp = true;
 148
 149         /*
 150          * Tell the core what device type specific functions should
 151          * be run on either side of buffer capture enable / disable.
 152          */
 153         buffer->setup_ops = &iio_simple_dummy_buffer_setup_ops;
 154         buffer->owner = THIS_MODULE;
 155
 156         /*
 157          * Configure a polling function.
 158          * When a trigger event with this polling function connected
 159          * occurs, this function is run. Typically this grabs data
 160          * from the device.
 161          *
 162          * NULL for the top half. This is normally implemented only if we
 163          * either want to ping a capture now pin (no sleeping) or grab
 164          * a timestamp as close as possible to a data ready trigger firing.
 165          *
 166          * IRQF_ONESHOT ensures irqs are masked such that only one instance
 167          * of the handler can run at a time.
 168          *
 169          * "iio_simple_dummy_consumer%d" formatting string for the irq 'name'
 170          * as seen under /proc/interrupts. Remaining parameters as per printk.
 171          */
 172         indio_dev->pollfunc = iio_alloc_pollfunc(NULL,
 173                                                  &iio_simple_dummy_trigger_h,
 174                                                  IRQF_ONESHOT,
 175                                                  indio_dev,
 176                                                  "iio_simple_dummy_consumer%d",
 177                                                  indio_dev->id);
 178
 179         if (indio_dev->pollfunc == NULL) {
 180                 ret = -ENOMEM;
 181                 goto error_free_buffer;
 182         }
 183
 184         /*
 185          * Notify the core that this device is capable of buffered capture
 186          * driven by a trigger.
 187          */
 188         indio_dev->modes |= INDIO_BUFFER_TRIGGERED;
 189         return 0;
 190
 191 error_free_buffer:
 192         iio_kfifo_free(indio_dev->buffer);
 193 error_ret:
 194         return ret;
 195
 196 }
 197
 198 /**
 199  * iio_simple_dummy_unconfigure_buffer() - release buffer resources
 200  * @indo_dev: device instance state
 201  */
 202 void iio_simple_dummy_unconfigure_buffer(struct iio_dev *indio_dev)
 203 {
 204         iio_dealloc_pollfunc(indio_dev->pollfunc);
 205         iio_kfifo_free(indio_dev->buffer);
 206 }