Hi Chris, > I don't really know devices exporting wluns by default. The wording in the latests SPC-4 draft I have says: That's true. In fact further finding showed me this: UFS device specification has explicitly mentioned the purpose of SELECT REPORT field when its set to 00h. When SELECT REPORT field is cleared, device should only report LUs which support peripheral device addressing method. Even UFS conformance test specification seems to confirm this explicitly. Hence if the UFS device adhere the UFS device specification then its expected for device to not report the W-LUs when SELECT REPORT is 00h. But I have seen one UFS device vendor specifically reporting w-lus even when select report is cleared. I am going to follow up them to fix their behavior. But for now, I guess we are on same page that device shouldn't report W-LUS when SELECT REPORT field is cleared. >> For now in this patch, we will skip modifying SELECT REPORT field but >> we would still require the other part of this patch for fixing the >> scsi_device type to wlun (sdev->type = TYPE_WLUN). Hence we will >> change the commit text accordingly to reflect the exact purpose of the change. > Yes, please resend this change as a separate patch with an updated description. I'd love to merge the whole ufs update for this merge window, so a timeline resent would be appreciated. Yes, rest of the part in this patch would still remain applicable with updated description. We will send it soon along with one more patch in UFS driver which would manually add scsi_device instance for the UFS W-LUs. Regards, Subhash -----Original Message----- From: linux-scsi-owner@xxxxxxxxxxxxxxx [mailto:linux-scsi-owner@xxxxxxxxxxxxxxx] On Behalf Of 'Christoph Hellwig' Sent: Monday, September 22, 2014 7:29 AM To: Subhash Jadavani Cc: 'Dolev Raviv'; James.Bottomley@xxxxxxxxxxxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx; linux-scsi-owner@xxxxxxxxxxxxxxx; linux-arm-msm@xxxxxxxxxxxxxxx; santoshsy@xxxxxxxxx; 'Sujit Reddy Thumma'; 'Martin K. Petersen' Subject: Re: [PATCH V3 01/16] scsi: support well known logical units On Thu, Sep 18, 2014 at 12:12:22PM -0700, Subhash Jadavani wrote: > Hi Chris, > > While testing with another vendor's UFS devices, I realized that > SELECT REPORT need not to be set to 0x02 for making the device report the W-LUs. > Even when SELECT REPORT is set 0x00, this particular UFS device > reports the W-LUs so I looked at the SCSI specification in details and > it seems ideally device should report all the well-known logical units > (as it follows the extended logical unit addressing format) when SELECT REPORT is set 0x00. I don't really know devices exporting wluns by default. The wording in the latests SPC-4 draft I have says: 00h The list shall contain the logical units accessible to the I_T nexus with the following addressing methods (see SAM-4): a) Logical unit addressing method, b) Peripheral device addressing method; and c) Flat space addressing method. If there are no logical units, the LUN LIST LENGTH field shall be zero. 01h The list shall contain only well known logical units, if any. If there are no well known logical units, the LUN LIST LENGTH field shall be zero. 02h The list shall contain all logical units accessible to the I_T nexus. SAM-4 defines WLUNs as their own addressing format in 4.6.11: Well known logical units are addressed using the well known logical unit extended address format (see table 28). Note that the reason I don't like reporting wluns by default is that so far we haven't come up with a use case for them in either the kernel or generic userspace. As long as usage of the wluns you want to support is confirmed to ufs, which is an unusually rightly coupled implementation of the initiator and target side I'd like to keep it isolated to ufs. If we ever come up with a more generic usage of other wluns we should also report them during the initial target scan. > For now in this patch, we will skip modifying SELECT REPORT field but > we would still require the other part of this patch for fixing the > scsi_device type to wlun (sdev->type = TYPE_WLUN). Hence we will > change the commit text accordingly to reflect the exact purpose of the change. Yes, please resend this change as a separate patch with an updated description. I'd love to merge the whole ufs update for this merge window, so a timeline resent would be appreciated. -- 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 -- 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
