Re: How to add/drop SCSI drives from within the driver?

[Matt Domsch <Matt_Domsch@dell.com>]

On Wed, Dec 15, 2004 at 02:42:21PM -0500, Mukker, Atul wrote:
> > 
> > Your management apps currently issue a private ioctl 
> > MEGAIOC_QNADAP which returns the number of 
> > megaraid_mm-handled adapters in the system.  How do you map a 
> > megaraid adapter number to a struct Scsi_Host device, to be 
> > sure you're acting on the controller you think you are?
>
> Megaraid_mm module maintains all the controllers on a list
> (mraid_mm_get_adapter), and each of the adapter maintains a pointer
> to the host object.

Yes, of course, I was unclear.  How do your userspace library and
management tools know that when they send commands via the
/dev/megaraid ioctls for adapter #5, that it's actually going to talk
to the PCI device at 0:03:06.0 (presumably the one it wants to do
configuration on) and not another megaraid-driven PCI device at
0:06:06.0 (which is not the one it wants) ?

If your management application doesn't care, or solves this in another
manner, please advise.

> Megaraid_mm is not a 'scsi' driver but only a conduit to pass the commands
> from application to the megaraid_mbox scsi module. 

But from your userspace tools perspective, it doesn't know that.  All
it knows is that (right now) it opens /dev/megaraid and issues ioctls
to a certain adapter number, yes?

What I'm trying to get to is a mapping, visible to userspace apps,
something like this.  You're right, megaraid_mm isn't a scsi driver,
so perhaps rather than having adapter0 with parent tree of
/sys/bus/scsi/drivers/megaraid_mm, it should be exposed with parent
tree /sys/module/megaraid_mm/, like so:

/sys
|-- class
|   `-- scsi_host
|       `-- host0
|-- devices
|   `-- pci0000:03
|       `-- 0000:03:06.0
`-- module
    |-- megaraid_mbox
    `-- megaraid_mm
        `-- adapter0
            |-- host0 -> ../../../class/scsi_host/host0
            `-- pci_dev -> ../../../devices/pci0000:03/0000:03:06.0

Your struct adapter_t has this mapping already, kernel-internal.  But
I think your userspace tools need to know the mapping too, to make
sure that adapter0 is the device they really intend to send management
commands to.

I think this question (do I have the right adapter), is analogous to
the question before (do I have the right HCTL tuple for this logical
drive), which my patch of last night may help address.

Thanks,
Matt

-- 
Matt Domsch
Sr. Software Engineer, Lead Engineer
Dell Linux Solutions linux.dell.com & www.dell.com/linux
Linux on Dell mailing lists @ http://lists.us.dell.com