From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Christie Subject: Re: [PATCH] cpnvert scsi_debug to use virtual host bus Date: Tue, 15 Feb 2005 10:48:34 -0800 Message-ID: <42124402.1060300@cs.wisc.edu> References: <420D5E03.2020409@cs.wisc.edu> <421184DC.8010900@torque.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Received: from sabe.cs.wisc.edu ([128.105.6.20]:63400 "EHLO sabe.cs.wisc.edu") by vger.kernel.org with ESMTP id S261815AbVBOSsv (ORCPT ); Tue, 15 Feb 2005 13:48:51 -0500 In-Reply-To: <421184DC.8010900@torque.net> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: dougg@torque.net Cc: linux-scsi Douglas Gilbert wrote: > Mike Christie wrote: > >> The attach patch converts scsi_debug to use the virtual scsi bus. >> It was built against scsi-rc-fixes-2.6. >> >> The interface has changed a little. Here is an >> example of adding and removing a single host: >> >> cd /sys/bus/scsi_host/drivers/scsi_debug >> [root@mina scsi_debug]# ls >> add_host dev_size_mb every_nth module num_parts opts scsi_level >> delay dsense max_luns num_hosts num_tgts ptype >> [root@mina scsi_debug]# echo 1 > add_host >> [root@mina scsi_debug]# ls >> add_host dev_size_mb every_nth module num_parts opts scsi_level >> delay dsense max_luns num_hosts num_tgts ptype virt_host4 >> [root@mina scsi_debug]# cd virt_host4/ >> [root@mina virt_host4]# ls >> detach_state driver host4 power remove_host >> [root@mina virt_host4]# echo 1 > remove_host > > > Mike, > I have noticed a few differences in the scsi_debug > driver with this patch applied. > > Firstly, when loaded the scsi_debug driver has no hosts > and thus no devices. Previously it defaulted to 1 host, > 1 target and 1 lun (hence 1 device). Now a user needs > to do something like: > $ modprobe scsi_debug > $ cd /sys/bus/scsi_host/drivers/scsi_debug > $ echo 42 > add_host > This is just a result of me trying to emulate normal HW drivers. For example I did not see any that would add the bus's device (the device equivalent to a pci_dev for example), so this is why I was always just doing the additions from userspace. I can break out part of scsi_host_driver_add_host and export it so LLDs can call it and add hosts from the kernel for scsi_debug. > The next issue is the number passed to "add_host". > It doesn't matter, one host is added. When add_host > belonged to scsi_debug the number and sign of the > value sent to add_host was significant (and a negative > number tried to remove that number of hosts). > Perhaps we could get that capability back by making > "num_hosts" writeable. > I can easily add both behaviors back to the "add_host" attr. > Otherwise it looks good and fixes the "pseudo" bus > problem which prevented two or more drivers using > the "pseudo" bus at the same time. > > Doug Gilbert >