Date: Wed, 24 Mar 2004 02:22:32 -0500 From: "Steve Ireland" <stevei@black-star.net> To: <freebsd-questions@freebsd.org> Subject: Re: disconnecting keyboard: big trouble !?! Message-ID: <054801c41170$c69a8040$1a01a8c0@blackstar.net> References: <405FC8A6.5040708@users.sourceforge.net><200403231909.08496.peter.schuller@infidyne.com><20040323134234.T81524@gabby.gsicomp.on.ca> <200403232154.24863.peter.schuller@infidyne.com>
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----- Original Message ----- From: "Peter Schuller" <peter.schuller@infidyne.com> To: "Matthew Emmerton" <matt@gabby.gsicomp.on.ca> Cc: <ste@smxy.org>; <freebsd-questions@freebsd.org> Sent: Tuesday, March 23, 2004 15:54 Subject: Re: disconnecting keyboard: big trouble !?! > On Tuesday 23 March 2004 19.44, Matthew Emmerton wrote: <snip> > > FreeBSD should not be working around user's bad practices. > > It has *always* been a bad idea to hot-plug PS/2 peripherals, and > > until USB is the norm, will continue to be the case. > > Again I've never heard of anyone running into any kind of problems due to > this. And someone else recently posted about not being able to find any > conclusive information on this info at all while googling. So really I don't > consider it bad practice at all, since I have never heard of a failure, nor > seen any concrete evidence why it would actually be bad. > > -- > / Peter Schuller, InfiDyne Technologies HB Hello, I wasn't to post further to this to the list as it is not FreeBSD related, but it seems to be of community interest. Why is PS/2 different from USB? Leaving aside the different physical and electronic designs, the USB spec calls for hotplugging, and the PS/2 spec doesn't. The PS/2 IO spec, written in 1986-87 as part of IBM's Micro Channel architecture, doesn't mention hotplugging all. It probably never occurred to the original engineers that someone would try it. (Ever see a spark when plugging something into a wall socket?) Interestingly, every operating system I've used since PS/2 came on the market either had no way to detect a PS/2 device was hotplugged, or it was disabled by default. I believe that's for a reason. As always, whenever there is a blank spot in a spec, different companies fill it in differently, so too with PS/2 controllers. Here is what I have witnessed first-hand happen when hotplugging: works perfectly, fails to recognize the keyboard without power cycling, fails to recognize both the keyboard and mouse because they were in the "wrong" ports, and of course blows the MB. Also, just because it worked on one particular MB, don't assume that make and model is "safe." As I commented off-list, a likely scenario is Brand X buys its components from various suppliers that have various brands with various models within brands with various revisions within models; each of which may or may not support hotplugging. Ultimately, the question is, what will the particular controller on the motherboard in the box in front of you do when you hotplug it? Two methods exist for finding out: the smoke test (pull the plugs, put them back in, wait for smoke) and o-scoping the ports. Because I don't care for smoke tests and don't usually have a scope handy, I power down. Is it a hassle? Oh yeah, but not as big a hassle as replacing a MB in a box at a colo or datacenter or my desk at home, for that matter. For those with a perverse sense of humor, IBM has "extended" the PS/2 spec for optical mice, etc. but has not added hotplugging. The perverse part? You can hotplug some of their product lines. But you didn't hear that from me ;). Regards, Steve
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