Re: [hpoj-devel] scan lockups with PSC500

[<pa...@rc...>]

> Unfortunately, all of the log files I've made have this problem, and setting
> LINEBUF didn't seem to help.
> Very sluggish, but still hangs.  And the debug output still gets cut off
> occasionally.  I'm not sure how to fix that.
I'm not either.  It's a matter of syslogd racing to keep up with the log
messages spewing out of the kernel.  I added the LINEBUF facility as a
quick-and-dirty workaround to help me debug a specific problem in preparation
for releasing version 0.5.  When enabled, it gave me a rough trace of the
sequence certain lines in the code got executed, and the linebufDump()
function would print out the results at a convenient time.  It might be
useful here with some changes, perhaps to "log" status line values instead
of line numbers in the source code (or perhaps some bit-shifted combination
thereof.

> > Another interesting test would be to log the return code of
> parStatusRead()
> > right before setting event 7/12, and again after
> "SET_STATE(l,9,BUSY_TIME);"
> > but before "PAR_WAIT_SET_CLEAR(l,0,PAR_STATUS_NACK);".  Any status line
> > changes after event 7/12 might further suggest a peripheral-side timeout.
> 
> Event 7/12 is a parControlSetClear() which never calls parStatusRead().  Do
> you mean parControlRead() or do you mean check it during event 6 (which
> comes just before event 7, I presume)?  It looks like parStatusRead() gets
> called in PAR_WAIT_SET_CLEAR.
I meant to add an additional parStatusRead() (and printk the return value)
right before the parControlSetClear() for event 7/12, and another one after
SET_STATE but before PAR_WAIT_SET_CLEAR, just to see what the status lines
are showing.

> Does the 1284.4 specification outline all these events?  It would be very
> helpful to have a flowchart or state diagram showing how all these events
> are supposed to occur.
IEEE 1284-1994 (or 1284 for short) is the "Standard Signaling Method for
a Bidirectional Parallel Peripheral Interface for Personal Computers",
which describes these events in great detail.  1284.4 and MLC are
higher-level transport protocols which can theoretically operate over any
bidirectional link (such as parallel, USB, etc.).

David