libmems/iio_channel_impl.cc

// Copyright 2019 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <memory>
#include <string>

#include <base/logging.h>
#include <base/strings/stringprintf.h>

#include "libmems/common_types.h"
#include "libmems/iio_channel_impl.h"
#include "libmems/iio_device.h"

namespace libmems {

IioChannelImpl::IioChannelImpl(iio_channel* channel) : channel_(channel) {
  CHECK(channel_);
}

const char* IioChannelImpl::GetId() const {
  return iio_channel_get_id(channel_);
}

bool IioChannelImpl::IsEnabled() const {
  return iio_channel_is_enabled(channel_);
}

bool IioChannelImpl::SetEnabled(bool en) {
  if (en)
    iio_channel_enable(channel_);
  else
    iio_channel_disable(channel_);

  // this tool will not stick around listening to this channel,
  // all it needs to do is leave the channel enabled for Chrome to use;
  // so, we directly write to the scan elements instead of setting up
  // a buffer and keeping it enabled while we run (which wouldn't be long
  // enough anyway). we do not need to handle the non scan-element case for
  // the channels we care about.
  if (!iio_channel_is_scan_element(channel_))
    return true;

  std::string en_attrib_name = base::StringPrintf(
      "scan_elements/%s_%s_en",
      iio_channel_is_output(channel_) ? "out" : "in", GetId());
  int error = iio_channel_attr_write_bool(channel_, en_attrib_name.c_str(), en);
  if (error) {
    LOG(WARNING) << "could not write to " << en_attrib_name
                 << ", error: " << error;
    return false;
  }

  return true;
}

base::Optional<std::string> IioChannelImpl::ReadStringAttribute(
    const std::string& name) const {
  char data[kReadAttrBufferSize] = {0};
  ssize_t len =
      iio_channel_attr_read(channel_, name.c_str(), data, sizeof(data));
  if (len < 0) {
    LOG(WARNING) << "Attempting to read attribute " << name
                 << " failed: " << len;
    return base::nullopt;
  }
  return std::string(data, len);
}

base::Optional<int64_t> IioChannelImpl::ReadNumberAttribute(
    const std::string& name) const {
  long long val = 0;  // NOLINT(runtime/int)
  int error = iio_channel_attr_read_longlong(channel_, name.c_str(), &val);
  if (error) {
    LOG(WARNING) << "Attempting to read attribute " << name
                 << " failed: " << error;
    return base::nullopt;
  }
  return val;
}

}  // namespace libmems