RE: [PATCH V3 01/16] scsi: support well known logical units

["Subhash Jadavani" <subhashj@codeaurora.org>]

> If those are the only LUs you specificly need I'd suggest you just
manually call scsi_add_device from your driver for those instead of listing
them in REPORT_LUNS and making them part of the normal LUN scan. 

Yes, we can do that but not sure what would be advantage of making the LLDs
to add these ad-hoc hooks instead of scsi_scan handle it on its own and
leaving the LLDs from adding them explicitly? Do you foresee any issues
(other than few extra scsi_device instances which may not be useful all scsi
devices) with scsi_scan scanning all the LUs (including well known LUs)?

Regards,
Subhash

-----Original Message-----
From: linux-scsi-owner@vger.kernel.org
[mailto:linux-scsi-owner@vger.kernel.org] On Behalf Of 'Christoph Hellwig'
Sent: Saturday, September 13, 2014 11:55 AM
To: Subhash Jadavani
Cc: 'Christoph Hellwig'; 'Dolev Raviv';
James.Bottomley@HansenPartnership.com; linux-scsi@vger.kernel.org;
linux-scsi-owner@vger.kernel.org; linux-arm-msm@vger.kernel.org;
santoshsy@gmail.com; 'Sujit Reddy Thumma'; 'Martin K. Petersen'
Subject: Re: [PATCH V3 01/16] scsi: support well known logical units

On Thu, Sep 11, 2014 at 05:41:18PM -0700, Subhash Jadavani wrote:
> 
> UFS device has supports 4 different well known logical units:
"REPORT_LUNS"
> (address: 01h), "UFS Device" (address: 50h), "RPMB" (address: 44h) and 
> "BOOT" (address: 30h).
> 
> UFS device's power management needs to be controlled by "POWER CONDITION"
> field of SSU (START STOP UNIT) command. But this "power condition"  
> field will take effect only when its sent to "UFS device" well known 
> logical unit
> (address: 50h) hence we require the scsi_device instance to represent 
> this logical unit in order for the UFS host driver to send the SSU 
> command for power management.
> 
> We also require the scsi_device instance for "RPMB" (Replay Protected 
> Memory
> Block) LU so user space process can control this LU.

If those are the only LUs you specificly need I'd suggest you just manually
call scsi_add_device from your driver for those instead of listing them in
REPORT_LUNS and making them part of the normal LUN scan.  One advantage of
the well known LUNs is that you always know where in the LUN namespace they
are :)

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