Streaming DEV Structures
7-32
❏ mode specifies whether the device is an input (DEV_INPUT) or output
(DEV_OUTPUT) device.
❏ devid is the device ID.
❏ params is a generic pointer to any device-specific parameters. Some
devices have additional parameters which are found here.
❏ object is a pointer to the device object. Most devices create an object that
is referenced in successive device operations.
❏ fxns is a DEV_Fxns structure containing the driver’s functions. This
structure is usually a copy of Dxx_FXNS, but it is possible for a driver to
dynamically alter these functions in Dxx_open.
❏ timeout specifies the number of system ticks that SIO_reclaim will wait for
I/O to complete.
❏ align specifies the buffer alignment.
❏ callback specifies a pointer to a channel-specific callback structure. The
DEV_Callback structure contains a callback function and two function
arguments. The callback function is typically SWI_andnHook or a similar
function that posts a SWI. Callbacks can only be used with the
issue/reclaim model. This callback allows SIO objects to be used with
SWI threads.
Only the object and fxns fields should ever be modified by a driver’s functions.
These fields are essentially output parameters of Dxx_open.
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