Re: [Qemu-devel] [Qemu-ppc] [PATCH] spapr_vscsi: Fix REPORT_LUNS handling

[Nathan Whitehorn <nwhitehorn@freebsd.org>]

On 01/03/14 08:27, Paolo Bonzini wrote:
> Il 02/01/2014 19:23, Nathan Whitehorn ha scritto:
>>>> Let me try to grasp what you're doing here. You're trying to
>>>> figure out how many devices there are attached to the bus. For
>>>> every device you reserve a buffer block. Lun0 is mandatory, all
>>>> others are optional.
>>>>
>>>> First off, I think the code would be easier to grasp if you'd
>>>> count "number of entries" rather than "number of bytes". That way
>>>> we don't have to mentally deal with the 8 byte block
>>>> granularity.
>>>>
>>>> Then IIUC you're jumping through a lot of hoops to count lun0 if
>>>> it's there, but keep it reserved when it's not there. Why don't
>>>> you just always reserve entry 0 for lun0? In the loop where
>>>> you're actually filling in data you just skip lun0. Or is lun0 a
>>>> terminator and always has to come last?
> This is simply because you should not report lun 0 twice; even if it is
> not defined, LUN 0 is there as a dummy device that only answers a
> handful of commands (including INQUIRY and REPORT LUNS).  There are many
> ways to write it, but unless you use GArray or something like that, it
> will look very much like Nathan and hw/scsi/scsi-bus.c's code.
>
> Paolo

I've sent a new version of this patch reflecting the discussion here.
Please let me know if I have missed anything.
-Nathan