[Info-vax] QIO Writes to a mailbox

[Bob Koehler]

In article <j932ro$42j$1 at Iltempo.Update.UU.SE>, Johnny Billquist <bqt at softjar.se> writes:
> 
> It is possible for drivers to have pre-queueing hooks invoked. Those 
> could in theory also copy the data somewhere.

   Generally, buffered I/O devices copy outgoing data to a system
   buffer dureing the FDT routines, which are before $QIO returns.

   But, of course, direct I/O devices do not, and any individual
   driver can do it's own thing, so it's a bad idea to assume knowledge
   of what goes on under the covers of $QIO unless you wrote the code.