Staging: IIO: Direct digital synthesis abi documentation

Changes since RFC/v1:
IIO: Apply list review feedback:

Apply list review feedback:
	Restructure documentation according to list feedback.
	Rename attributes to fit IIO convention used in other drivers.
	Fix typos.
	Provide ddsX_out_enable as opposed to ddsX_out_disable

Changes since v2:
IIO: sysfs-bus-iio-dds: Apply more list review feedback

	Fix mixture of X and [n] notation for indices.
	Fix some wording in the descriptions.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/staging/iio/Documentation/sysfs-bus-iio-dds b/drivers/staging/iio/Documentation/sysfs-bus-iio-dds
new file mode 100644 (file)
index 0000000..ffdd547
--- /dev/null
+++ b/drivers/staging/iio/Documentation/sysfs-bus-iio-dds
@@ -0,0 +1,93 @@
+
+What:          /sys/bus/iio/devices/.../ddsX_freqY
+KernelVersion: 2.6.37
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Stores frequency into tuning word Y.
+               There will be more than one ddsX_freqY file, which allows for
+               pin controlled FSK Frequency Shift Keying
+               (ddsX_pincontrol_freq_en is active) or the user can control
+               the desired active tuning word by writing Y to the
+               ddsX_freqsymbol file.
+
+What:          /sys/bus/iio/devices/.../ddsX_freqY_scale
+KernelVersion: 2.6.37
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Scale to be applied to ddsX_freqY in order to obtain the
+               desired value in Hz. If shared across all frequency registers
+               Y is not present. It is also possible X is not present if
+               shared across all channels.
+
+What:          /sys/bus/iio/devices/.../ddsX_freqsymbol
+KernelVersion: 2.6.37
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Specifies the active output frequency tuning word. The value
+               corresponds to the Y in ddsX_freqY. To exit this mode the user
+               can write ddsX_pincontrol_freq_en or ddsX_out_enable file.
+
+What:          /sys/bus/iio/devices/.../ddsX_phaseY
+KernelVersion: 2.6.37
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Stores phase into Y.
+               There will be more than one ddsX_phaseY file, which allows for
+               pin controlled PSK Phase Shift Keying
+               (ddsX_pincontrol_phase_en is active) or the user can
+               control the desired phase Y which is added to the phase
+               accumulator output by writing Y to the en_phase file.
+
+What:          /sys/bus/iio/devices/.../ddsX_phaseY_scale
+KernelVersion: 2.6.37
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Scale to be applied to ddsX_phaseY in order to obtain the
+               desired value in rad. If shared across all phase registers
+               Y is not present. It is also possible X is not present if
+               shared across all channels.
+
+What:          /sys/bus/iio/devices/.../ddsX_phasesymbol
+KernelVersion: 2.6.37
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Specifies the active phase Y which is added to the phase
+               accumulator output. The value corresponds to the Y in
+               ddsX_phaseY. To exit this mode the user can write
+               ddsX_pincontrol_phase_en or disable file.
+
+What:          /sys/bus/iio/devices/.../ddsX_pincontrol_en
+What:          /sys/bus/iio/devices/.../ddsX_pincontrol_freq_en
+What:          /sys/bus/iio/devices/.../ddsX_pincontrol_phase_en
+KernelVersion: 2.6.37
+Contact:       linux-iio@vger.kernel.org
+Description:
+               ddsX_pincontrol_en: Both, the active frequency and phase is
+               controlled by the respective phase and frequency control inputs.
+               In case the device in question allows to independent controls,
+               then there are dedicated files (ddsX_pincontrol_freq_en,
+               ddsX_pincontrol_phase_en).
+
+What:          /sys/bus/iio/devices/.../ddsX_out_enable
+What:          /sys/bus/iio/devices/.../ddsX_outY_enable
+KernelVersion: 2.6.37
+Contact:       linux-iio@vger.kernel.org
+Description:
+               ddsX_outY_enable controls signal generation on output Y of
+               channel X. Y may be suppressed if all channels are
+               controlled together.
+
+What:          /sys/bus/iio/devices/.../ddsX_outY_wavetype
+KernelVersion: 2.6.37
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Specifies the output waveform.
+               (sine, triangle, ramp, square, ...)
+               For a list of available output waveform options read
+               available_output_modes.
+
+What:          /sys/bus/iio/devices/.../ddsX_outY_wavetype_available
+KernelVersion: 2.6.37
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Lists all available output waveform options.