On Thu, Sep 28, 2006 at 04:15:05PM -0400, Douglas Gilbert wrote: > > + scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are > > + discovered. async scans them in kernel threads, > > + allowing boot to proceed. none ignores them, expecting > > + user space to do the scan. > > Matthew, > I like the "none" which is no doubt a place holder at > the moment. I wouldn't say it was extensively tested, but no, there's checks for the value "none" and it does indeed fail to discover any devices ;-) > For the user space to do discovery, it either needs an out > of band mechanism (e.g. IP) or the ability to talk to a > host in the absence of any "devices" (targets or logical units). > That requires a device node (e.g. /dev/mptctl) or something > equivalent in sysfs (yuk). I must confess to having not thought about how userspace probes a scsi host to find out what devices are behind it. This was a feature that James asked for and it was easy to add. > Your "none" explanation could be slightly extended to say > that the LLD (and/or its firmware) might do the discovery. Note that by specifying "none", not even the FC/SAS/etc drivers can register targets as they find them -- it really is up to userspace to echo scsi-add-single-device H C T L >/proc/scsi/scsi I'm a little uncomfortable with that, and I'd be open to adding another word that means "no scanning, but if the driver's been told about the device by a switch, add it automatically, don't wait for userspace". I do think that none needs to mean none though. > As an > example the SAS-2 draft now has self-configuring expanders > (the terms "edge" and "fanout" have been dropped) which > effectively discover the topology and track changes, configuring > themselves and dumber expanders as required. Then host discovery > becomes importing the topology from an external device. However > not all devices may be visible to self-configuring expanders > (e.g. a SATA disk could be directly attached to a SAS HBA). So > some extra work may be required. That would be up to userspace in the "none" view of the world. I could see people wanting to ignore the self-configuring expander and impose a new (incorrect) topology on the system. BTW, there'll be a lucky version 13 in a few minutes ... shost_for_each_device_safe isn't. - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
