Re: OT: Recommend good multi-drive enclosure chipset?

Mark Knecht wrote:
>>Hi Stefan,

Hi Mark,
good to read you here again.

>> Anyway, was there possibly some tool that allows us to set gap
>>count by hand? I cannot remember.

1394commander is a command line tool that lets you send phy packets,
reset the bus, and much more. It can be used with its own command line
interface or you just pass commands through a pipe or from a file.
Command 'p' sends a phy packet, 'br short' issues a short bus reset,
'help' shows available commands.

echo p 0x00450000 | 1394commander # for up to one cable hop
echo p 0x004a0000 | 1394commander # for up to four cable hops

This is the gap count and a fixed value of 0x40 OR'ed together and
rolled two bytes to the left. The gap count is reset to its default
value of 63 after two bus resets or a burst of resets like when a device
is connected. Therefore the above command should be repeated after each
bus reset. Furthermore, the spec says a bus reset should be triggered
immediately after sending such a phy packet _and_ the then broadcast
selfIDs should be checked if every PHY got the correct gap count. But in
practice, the reset is not necessary. (Well, Mark knows all that, but
maybe someone else wants to try this too.)

>> Even a tool that lets me read the Py
>>registers and see what gap count is set at would be helpful.
...
> So as soon as I sent that previous note I thought of gscanbus which
> does allow me to see gap count, but it only seems to show me one of
> the two OHCI controllers in my system. man gscanbus and gscanbus
> --help return nothing.

There is a patch at the feature tracker at gscanbus' homepage that adds
a command line parameter to select the controller. Else gscanbus always
uses controller 0. Maybe one or another Linux distro provides gscanbus
with the patch already applied, but most don't, probably.

Note that gscanbus does not show the _current_ gap count but rather the
one from the last bus reset.

-- 
Stefan Richter
-=====-=-=-= -=-- -====
http://arcgraph.de/sr/
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