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##

# 3.3.4.13 USB_HOST_AUDIO_V1_FeatureUnitChannelVolumeGet Function

## C

    USB_HOST_AUDIO_V1_RESULT USB_HOST_AUDIO_V1_FeatureUnitChannelVolumeGet(
        USB_HOST_AUDIO_V1_OBJ audioObj,
        USB_HOST_AUDIO_V1_CONTROL_ENTITY_OBJ entityObject,
        USB_HOST_AUDIO_V1_REQUEST_HANDLE * requestHandle,
        uint8_t channelNumber,
        uint16_t * volume
    );

## Description

This function schedules a get current volume control request to the specified channel. Prior to calling this function the user should check if volume control exists on the specified channel by calling the USB_HOST_AUDIO_V1_FeatureUnitChannelVolumeExists function.

If the request was scheduled successfully, the requestHandle parameter will contain a request handle that uniquely identifies this request. If the request could not be scheduled successfully, requestHandle will contain USB_HOST_AUDIO_V1_REQUEST_HANDLE_INVALID.

When the control request completes, the Audio v1.0 Client Driver will call the callback function that was set using the USB_HOST_AUDIO_V1_EntityRequestCallbackSet function. The context parameter specified here will be returned in the callback.

## Parameters

Parameters | Description
audioObj | USB Host Audio v1.0 Device object
entityObject | Audio control entity object
requestHandle | Output parameter that will contain the handle to this request
channelNumber | Channel number to which the volume control is addressed
volume | Output parameter that will contain the current volume when a request is completed and a callback is received

## Returns

- USB_HOST_AUDIO_V1_RESULT_SUCCESS - The request was scheduled successfully. requestHandle will contain a valid request handle.
- USB_HOST_AUDIO_V1_RESULT_BUSY - The control request mechanism is currently busy. Retry the request.
- USB_HOST_AUDIO_V1_RESULT_FAILURE - An unknown failure occurred. requestHandle will contain USB_HOST_AUDIO_V1_0_REQUEST_HANDLE_INVALID.
- USB_HOST_AUDIO_V1_RESULT_PARAMETER_INVALID - The data pointer or requestHandle pointer is NULL.

## Remarks

None.