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SubjectRe: [PATCH] Fix SCSI proc oops


On Sat, 14 Oct 2000, Torben Mathiasen wrote:

> On Sat, Oct 14 2000, David S. Miller wrote:
> > Date: Sat, 14 Oct 2000 11:43:09 +0200
> > From: Torben Mathiasen <torben@kernel.dk>
> >
> > David, why is tpnt->proc_name NULL on sparc for devices not
> > existing? Every driver has this as part of their tpnt struct, so
> > it doesn't matter if the underlying device really exists.
> >
> > In the mentioned case it would be NULL on all architectures, not just
> > Sparc ;-) (it happens on ix86 too, ix86 is different only because it
> > does not trap kernel NULL pointer derefences during bootup for some
> > odd reason)
> >
> > Here is what happens:
> >
> > scsi_register_host()
> > tpnt->present = tpnt->detect(tpnt);
> > /* tpnt->present is zero since no such adapters were found */
> >
> > If no hosts are detected the driver is under no obligation to
> > initialize the tpnt->proc_name field. For example,
> > sym53c8xx.c:sym53c8xx_detect() does not if PCI is not present and this
> > is the specific case hit on my SBUS-only workstation :-)
> >
> > Subsequently scsi_unregister_host() is called for this TPNT and
> > this is where the NULL pointer is hit.
> >
>
> Ahh, the drivers I looked at all had proc_name as part of their:
>
> define IN2000 {
> bla: bla,
> proc_name: IN2000,
>
> }
>
> structure. I see your point now.
>
> Are there any reason why sym53c8xx and others initialize proc_name only
> if an adapter was actually found (or in the sym case, if a pcibus was
> found)?

The [sym|ncr]53c8xx drivers do initialize the proc fs stuff (proc_name for
recent kernels) in the Scsi_Host_Template if PCI is present and user wants
the controllers to be registered in the proc FS. On the other hand, the
`proc_name' field appeared in some 2.3.X kernel version (sym53c8xx says
Linux-2.3.27). In previous kernel versions, SCSI drivers had to make
`proc_dir' field point to a `proc_dir' structure that allowed proc/FSing
the controller to be optionnable.

We have to decide if we want proc/FSing SCSI controllers (event when none
will be attached or BUS does not even exist) to be optionnal or not.
- If it is optionnal, then proc_name=NULL should be interpreted as
proc/FSing option disabled.
- Otherwise, the proc_name field should be required to be not NULL.

Gérard.

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