> -----Original Message----- > From: James Bottomley [mailto:jbottomley@xxxxxxxxxxxxx] > Sent: Thursday, April 04, 2013 11:15 AM > To: KY Srinivasan > Cc: gregkh@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > devel@xxxxxxxxxxxxxxxxxxxxxx; ohering@xxxxxxxx; hch@xxxxxxxxxxxxx; linux- > scsi@xxxxxxxxxxxxxxx > Subject: Re: scanning for LUNs > > On Thu, 2013-04-04 at 08:12 -0700, K. Y. Srinivasan wrote: > > Here is the code snippet for scanning LUNS (drivers/scsi/scsi_scan.c in function > > __scsi_scan_target()): > > > > /* > > * Scan LUN 0, if there is some response, scan further. Ideally, we > > * would not configure LUN 0 until all LUNs are scanned. > > */ > > res = scsi_probe_and_add_lun(starget, 0, &bflags, NULL, rescan, NULL); > > if (res == SCSI_SCAN_LUN_PRESENT || res == > SCSI_SCAN_TARGET_PRESENT) { > > if (scsi_report_lun_scan(starget, bflags, rescan) != 0) > > > > > > So, if we don't get a response while scanning LUN0, we will not use > > scsi_report_lun_scan(). > > On Hyper-V, the scsi emulation on the host does not treat LUN0 as > > anything special and we > > could have situations where the only device under a scsi controller is > > at a location other than 0 > > or 1. In this case the standard LUN scanning code in Linux fails to > > detect this device. Is this > > behaviour expected? Why is LUN0 treated differently here. Looking at > > the scsi spec, I am not sure > > if this is what is specified. Any help/guidance will be greatly > > appreciated. > > Why don't you describe the problem. We can't scan randomly a bunch of > LUNs hoping for a response (the space is 10^19). SAM thinks you use > LUNW for this, but that's not well supported. We can't annoy USB > devices by probing with REPORT LUNS, so conventionally most arrays > return something for LUN0 even if they don't actually have one (That's > what the peripheral qualifier codes are supposed to be about). We > translate PQ1 and PQ2 to SCSI_SCAN_TARGET_PRESENT, which means no LUN, > but there is a target to scan here. > > If you're sending back an error to an INQUIRY to LUN0, then you're out > of spec. The SCSI standards say: > > SPC3 6.4.1: In response to an INQUIRY command received by an > incorrect logical unit, the SCSI target device shall return the > INQUIRY data with the peripheral qualifier set to the value > defined in 6.4.2. The INQUIRY command shall return CHECK > CONDITION status only when the device server is unable to return > the requested INQUIRY data Thanks James. I will further investigate the issue on our platform. Regards, K. Y > > James > > > James > > _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
