From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 8 Jan 2001 16:49:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 8 Jan 2001 16:49:13 -0500 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:46093 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id ; Mon, 8 Jan 2001 16:49:05 -0500 From: Russell King Message-Id: <200101082150.f08Lots13085@flint.arm.linux.org.uk> Subject: Re: The advantage of modules? To: meissner@spectacle-pond.org (Michael Meissner) Date: Mon, 8 Jan 2001 21:50:55 +0000 (GMT) Cc: ookhoi@dds.nl (Ookhoi), meissner@spectacle-pond.org (Michael Meissner), linux-kernel@vger.kernel.org In-Reply-To: <20010108140521.C11682@munchkin.spectacle-pond.org> from "Michael Meissner" at Jan 08, 2001 02:05:21 PM X-Location: london.england.earth.mulky-way.universe X-Mailer: ELM [version 2.5 PL3] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Michael Meissner writes: > Quoting from drivers/scsi/scsi.c: > > /* > * Usage: echo "scsi add-single-device 0 1 2 3" >/proc/scsi/scsi > * with "0 1 2 3" replaced by your "Host Channel Id Lun". > * Consider this feature BETA. > * CAUTION: This is not for hotplugging your peripherals. As > * SCSI was not designed for this you could damage your > * hardware ! > * However perhaps it is legal to switch on an > * already connected device. It is perhaps not > * guaranteed this device doesn't corrupt an ongoing data transfer. > */ > > so my take is unless you explicitly use hotplug devices (I wasn't), that > it is much safer to unload the driver, unattach/attach scsi devices, and > then reload the driver (which will scan the scsi bus for devices), which > you need modules for. I don't believe that is what it's trying to say. There have been instances in the past where unplugging a SCSI device from a powered on SCSI bus can result in blown terminator power fuses and the like. Whether this still applies today, I don't know (are active terminators better or worse than passive when it comes to this type of thing?) However, what I do know is the following, and I learnt it the hard way: I once had a machine and other stuff on a 4-way mains connector block that has been used for many years. Unknown to me, the earth wire had become intermittent. I was just about to connect another peripheral which was directly connected to the wall socket to this computer, and I happened to touch the connector body on both the peripheral and the computer. I now know what a shock of >120V feels like. Now, imagine what would happen if you connect a SCSI device, where this condition exists, and the first thing that makes contact is the SCSI databus. Say goodbye to most, if not all devices on that SCSI bus. _____ |_____| ------------------------------------------------- ---+---+- | | Russell King rmk@arm.linux.org.uk --- --- | | | | http://www.arm.linux.org.uk/personal/aboutme.html / / | | +-+-+ --- -+- / | THE developer of ARM Linux |+| /|\ / | | | --- | +-+-+ ------------------------------------------------- /\\\ | - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/