[PATCH v4 09/12] IIO: ADC: add stm32 DFSDM support for PDM microphone

On Fri, 24 Nov 2017 15:52:26 +0100
Arnaud Pouliquen [off-list ref] wrote:

On 11/19/2017 03:18 PM, Jonathan Cameron wrote:

quoted

On Thu, 9 Nov 2017 11:12:31 +0100
Arnaud Pouliquen [off-list ref] wrote:
  

quoted

This code offers a way to handle PDM audio microphones in
ASOC framework. Audio driver should use consumer API.
A specific management is implemented for DMA, with a
callback, to allows to handle audio buffers efficiently.

Signed-off-by: Arnaud Pouliquen <redacted>  

A few minor points inline.? I'm not sure I really 'like' the
solution we've ended up with currently but if it works it will
do just fine for now :)

Jonathan

  

quoted

---
V3 -> V4 changes:
? - Merge audio implementation in stm32-dfsdm-adc.c instead of creating separate file
? - Add sysfs document for exported attributes

? .../ABI/testing/sysfs-bus-iio-dfsdm-adc-stm32????? |? 22 +
? drivers/iio/adc/stm32-dfsdm-adc.c????????????????? | 517 ++++++++++++++++++++-
? include/linux/iio/adc/stm32-dfsdm-adc.h??????????? |? 27 ++
? 3 files changed, 562 insertions(+), 4 deletions(-)
? create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-dfsdm-adc-stm32
? create mode 100644 include/linux/iio/adc/stm32-dfsdm-adc.h

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-dfsdm-adc-stm32 b/Documentation/ABI/testing/sysfs-bus-iio-dfsdm-adc-stm32
new file mode 100644
index 0000000..0ce5508
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-iio-dfsdm-adc-stm32

@@ -0,0 +1,22 @@
+What:??????????????? /sys/bus/iio/devices/iio:deviceX/in_voltage_audio_sampling_rate
+KernelVersion:?????? 4.14
+Contact:???? arnaud.pouliquen at st.com
+Description:
+???????????? For audio purpose only.
+???????????? Used by audio driver to set/get the audio sampling rate.
+???????????? Reading returns current audio sample frequency.
+???????????? Writing value before starting conversions.  

I would like to see a note here on why sampling_frequency can't be used for
this purpose.  

The IIO_CHAN_INFO_SAMP_FREQ can not be used because consumer API allows
only to access to ext_info attributes.
An alternate is to export channel attribute functions the consumer API.
- iio_read_channel_attribute (already exist)
- iio_write_channel_attribute

Yes - add these please.  Just not been a usecase before for the general write.

Please, tell me your preference.

<snip>

quoted

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+/**
+ * stm32_dfsdm_get_buff_cb - register a callback
+ *?? that will be called when DMA transfer period is achieved.  

Please run kernel-doc over this file. I'm fairly sure this isn't
quite meeting the spec...  

Sorry it is not crystal clear for me, could you detail what you would
mean by
"I'm fairly sure this isn't quite meeting the spec.."?

I don't think it lets you have multiple lines for the short description
IIRC.  Not sure about the indented function parameters.. Might be
new since I last looked!

quoted

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+ *
+ * @iio_dev: Handle to IIO device.
+ * @cb: pointer to callback function.
+ *?? @data: pointer to data buffer
+ *?? @size: size in byte of the data buffer
+ *?? @private: pointer to consumer private structure
+ * @private: pointer to consumer private structure
+ */