The AUXDM_SETVOLUME message requests a user-mode driver to set the volume level for the specified auxiliary audio device.
Parameters
uDeviceId
Device identifier (0, 1, 2, and so on) for the target device.
uMsg
AUXDM_SETVOLUME
dwUser
Not used.
dwParam1
A DWORD containing the volume setting.
dwParam2
Not used.
Return Value
The driver should return MMSYSERR_NOERROR if the operation succeeds. Otherwise it should return one of the MMSYSERR error codes defined in mmsystem.h.
Comments
A client sends the AUXDM_SETVOLUME message by calling the user-mode driver’s auxMessage entry point, passing the specified parameters.
Support for this message by user-mode drivers is optional. If the driver supports AUXDM_SETVOLUME, it must support AUXDM_GETVOLUME.
The volume value is specified by dwParam1 as follows.
| Channel | Portion of dwParam1 Used |
| Left channel | Low word |
| Right channel | High word |
| Single channel | Low word |
A value of zero is silence, and a value of 0xFFFF is full volume.
The kernel-mode driver might not support the full 16 bits of volume control and can truncate the lower bits. However, the original value requested with AUXDM_SETVOLUME should be returned with AUXDM_GETVOLUME.
Typically, the user-mode driver calls DeviceIoControl to send the kernel-mode driver an IOCTL_AUX_SET_VOLUME control code.