Date: Thu, 28 Aug 2008 18:01:09 +0100 From: Dieter <freebsd@sopwith.solgatos.com> To: Sean Bruno <sbruno@miralink.com> Cc: freebsd-firewire@freebsd.org Subject: Re: This is where I'm going with fwcontrol Message-ID: <200808290101.BAA25511@sopwith.solgatos.com> In-Reply-To: Your message of "Thu, 28 Aug 2008 16:49:05 PDT." <48B73971.90706@miralink.com>
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> send_phy_config() is causing the /dev/fwX device to generate a PHY > configuration Packet(IEEE 1394-1995 4.3.4.3) > <snippet from document> > It is possible to optimize Serial Bus performance for particular > configurations in the following ways: > a) Setting the gap_count used by all nodes to a smaller value > (appropriate to the actual worst-case number of > hops between any two nodes) > b) Forcing a particular node to be the root after the next bus > initialization (for example, in isochronous systems, > the root shall be cycle-master capable) > Both of these actions shall be done for remote nodes using the PHY > configuration packet shown in figure 4.20. (For the > local node, the PH_CONT.request service is used) The procedures for > using this PHY packet are described in clause > 7.3.5.2.1. > <end snippet> > > So, I think you are correct adjust_gap_count should become set_root_node > as that is what it does. > > A PHY Config packet should look like this: > Message ID Root ID R T Gap Count > 00(2 bits) (5 bits) 1 1 (6 bits) > > So the Root ID(-f in fwcontrol) can't be set to a value greater than > 0x3f(63) and the Gap Count can't be greater than 0x7f(127). An "R" > value of 1 means that this is a message to set the root ID. An "T" > value of 1 means that this is a message to set the gap count for all > nodes. If "R" and "T" are both 0, then the message is ignored. Thank you, this makes much more sense now! I was looking at controller registers, but it is building a packet. Suggestion: put something like the text above in a comment at the start of send_phy_config().
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