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  1. 16 9月, 2013 1 次提交
  3. 15 9月, 2013 1 次提交
    • P
      iio: Add INT_TIME (integration time) channel info attribute · 899d90bd
      由 Peter Meerwald 提交于 
      Integration time is in seconds; it controls the measurement
time and influences the gain of a sensor.

There are two typical ways that scaling is implemented in a device:
1) input amplifier,
2) reference to the ADC is changed.
These both result in the accuracy of the ADC varying (by applying its
sampling over a more relevant range).

Integration time is a way of dealing with noise inherent in the analog
sensor itself.  In the case of a light sensor, a mixture of photon noise
and device specific noise.  Photon noise is dealt with by either improving
the efficiency of the sensor, (more photons actually captured) which is not
easily varied dynamically, or by integrating the measurement over a longer
time period.  Note that this can also be thought of as an averaging of a
number of individual samples and is infact sometimes implemented this way.
Altering integration time implies that the duration of a measurement changes,
a fact the device's user may be interested in.

Hence it makes sense to distinguish between integration time and simple
scale. In some devices both types of control are present and whilst they
will have similar effects on the amplitude of the reading, their effect
on the noise of the measurements will differ considerably.

Used by adjd_s311, tsl4531, tcs3472
The following drivers have similar controls (and could be adapted):
* tsl2563 (integration time is controlled via CALIBSCALE among other things)
* tsl2583 (has integration_time device_attr, but driver doesn't use channels yet)
* tsl2x7x (has integration_time attr)
Signed-off-by: NPeter Meerwald <pmeerw@pmeerw.net>
Cc: Jon Brenner <jon.brenner@ams.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>
      899d90bd
  5. 01 9月, 2013 1 次提交
  7. 18 8月, 2013 1 次提交
  9. 04 8月, 2013 2 次提交
  11. 03 7月, 2013 1 次提交
  13. 18 3月, 2013 2 次提交
  15. 21 11月, 2012 1 次提交
  17. 10 11月, 2012 1 次提交
  19. 19 10月, 2012 1 次提交
  21. 18 9月, 2012 1 次提交
  23. 07 9月, 2012 1 次提交
  25. 04 9月, 2012 3 次提交
  27. 28 8月, 2012 1 次提交
  29. 10 7月, 2012 1 次提交
    • L
      iio: Add callback to check whether a scan mask is valid · 939546d1
      由 Lars-Peter Clausen 提交于 
      This is useful for cases where the number of valid scan masks grows
exponentially, but it is rather easy to check whether a mask is valid or not
programmatically.

An example of such a case is a device with multiple ADCs where each ADC has a
upstream MUX, which allows to select from a number of physical channels.

  +-------+   +-------+
  |       |   |       | --- Channel 1
  | ADC 1 |---| MUX 1 | ---   ...
  |       |   |       | --- Channel M
  +-------+   +-------+

     .            .            .
     .            .            .
     .            .            .

  +-------+   +-------+
  |       |   |       | --- Channel M * N + 1
  | ADC N |---| MUX N | ---       ...
  |       |   |       | --- Channel M * N + M
  +-------+   +-------+

The number of necessary scan masks for this case is (M+1)**N - 1, on the other
hand it is easy to check whether subsets for each ADC of the scanmask have only
one bit set.
Signed-off-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>
      939546d1
  31. 19 6月, 2012 1 次提交
  33. 13 6月, 2012 4 次提交
  35. 05 6月, 2012 2 次提交
  37. 15 5月, 2012 2 次提交
  39. 30 4月, 2012 3 次提交
  41. 26 4月, 2012 1 次提交
  43. 25 4月, 2012 3 次提交
  45. 19 4月, 2012 2 次提交
  47. 14 4月, 2012 3 次提交