INT 21 - DOS 2+ - IOCTL - READ FROM CHARACTER DEVICE CONTROL CHANNEL
AX = 4402h
BX = file handle referencing character device
CX = number of bytes to read
DS:DX -> buffer
Return: CF clear if successful
AX = number of bytes actually read
CF set on error
AX = error code (01h,05h,06h,0Dh) (see AH=59h)
Note:   format of data is driver-specific (see below for some specific cases)
SeeAlso: AX=4403h,AX=4404h,INT 2F/AX=122Bh

See also: 214400

214402 - DOS 2+ - IOCTL - READ FROM CHARACTER DEVICE CONTROL CHANNEL