Specifications

Operating System Routines
EXE$READCHK, EXE$READCHKR
• Determines whether the specified buffer is write accessible for a read I/O
function, with one of the following results:
If the buffer allows write access, EXE$READCHKR sets IRP$V_FUNC in
IRP$W_STS and returns SS$_NORMAL to its caller.
If the buffer does not allow write access, EXE$READCHKR returns SS$_
ACCVIO status to its caller.
If the initial call was to EXE$READCHK, and EXE$READCHKR returns error
status, EXE$READCHK transfers control to EXE$ABORTIO to terminate the
I/O request. If the initial call was to EXE$READCHKR, and an error occurs,
EXE$READCHKR returns control to the driver. Otherwise, these routines return
success status to their callers.
A driver FDT routine that calls EXE$READCHKR must distinguish between
successful and unsuccessful status when it resumes, as shown in the following
example:
JSB G^EXE$READCHKR
BLBS R0,BUF_ACCESS_OK
BUF_ACCESS_FAIL:
;
; clean up this $QIO bookkeeping
;
JSB G^EXE$ABORTIO
BUF_ACCESS_OK:
.
.
.
;
;continue processing this I/O request
;
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