Re: [PATCH] scsi-misc-2.5 remove scsi_scan.c EVPD code

[James Bottomley <James.Bottomley@steeleye.com>]

On Mon, 2003-05-05 at 11:38, Patrick Mansfield wrote:
> As James said, we can get the uid from user space. This implies we need sg
> (or an equivalent solution).
> 
> If the id is required before any actual use of the device, we (sometimes?
> always?) need initramfs.

initramfs is only needed to find the root device.  All others can be
located later (although when depends on how the hotplug vs coldplug
issues are sorted out)

> There is a problem with trying to use sg before sg is attached - not sure
> how we can handle this. If sg could be opened generically and attached to
> any nexus (i.e. scsi_device) via ioctl, we could use it not only for id's,
> but for general user level scanning. Or maybe we can wait until after sg
> is attached to get id's.

You can now send SCSI commands directly to sd via the ioctl.

> We still have problems with potentially locking up some devices, and we
> will need some sort of black/white list for VPD usage, this would also
> have been needed for an in kernel implementation; [for user space] you
> would not need a kernel change to fix a problem (modify the black/white
> list or other such code to prevent a VPD from being sent to a particular
> device).

Yes.

> Plus, many of the devices do not return unique id's, even when VPD pages
> are supported (especially I'm told USB) - we need a white list or other
> such mechanism to tell us that id's are actually unique.

That's one of the reasons for moving itt: he heuristics are pretty
complex given the strange things devices seem to call "unique" (I can
even see devices where it's "get the label from the first available
fs").

James




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