NAME
OpenDevice -- gain access to a device
SYNOPSIS
error = OpenDevice(devName, unitNumber, iORequest, flags)
D0 A0 D0 A1 D1
BYTE OpenDevice(STRPTR,ULONG,struct IORequest *,ULONG);Links: IORequest
FUNCTION
This function opens the named device/unit and initializes the given I/O request block. Specific documentation on opening procedures may come with certain devices.
The device may exist in memory, or on disk; this is transparent to the OpenDevice caller.
A full path name for the device name is legitimate. For example "test:devs/fred.device". This allows the use of custom devices without requiring the user to copy the device into the system's DEVS: directory.
NOTES All calls to OpenDevice should have matching calls to CloseDevice!
Devices on disk cannot be opened until after DOS has been started.
As of V36 tasks can safely call OpenDevice, though DOS may open system requesters (e.g., asking the user to insert the Workbench disk if DEVS: is not online). You must call this function from a DOS Process if you want to turn off DOS requesters.
INPUTS
devName - requested device name
unitNumber - the unit number to open on that device. The format of the unit number is device specific. If the device does not have separate units, send a zero.
iORequest - the I/O request block to be returned with appropriate fields initialized.
flags - additional driver specific information. This is sometimes used to request opening a device with exclusive access.
RESULTS
error - Returns a sign-extended copy of the io_Error field of the IORequest. Zero if successful, else an error code is returned.
BUGS AmigaDOS file names are not case sensitive, but Exec lists are. If the library name is specified in a different case than it exists on disk, unexpected results may occur.
Prior to V36, tasks could not make OpenDevice calls requiring disk access (since tasks are not allowed to make dos.library calls). Now OpenDevice is protected from tasks.
SEE ALSO