Subject: [PATCH 4/5] [SCSI] Do not use platform_bus as a parent

From: [email-masked] (James Bottomley)
Date: Fri, 25 Jul 2014 07:46:56 -0700

On Fri, 2014-07-25 at 15:23 +0100, Pawel Moll wrote:
> The host devices without a parent were "forcefully adopted"
> by platform bus. This patch removes this assignment. In
> effect the dev_dev may be NULL now, which means ISA.
> 
> Cc: James E.J. Bottomley <[email-masked]>
> Cc: linux-scsi at vger.kernel.org
> Signed-off-by: Pawel Moll <[email-masked]>
> ---
> 
> This patch is a part of effort to remove references to platform_bus
> and make it static.
> 
> James, could you please have a look and advice if the change is
> correct? Would you happen to know the "real reasons" behind
> using the root platform_bus device a parent?

Yes, for DMA purposes, the parent cannot now be NULL; we'll get a panic
in the DMA transfers if it is.  A lot of the legacy ISA device on x86
and I thought some ARM SOC devices don't pass in the parent device, so
we hang them off a known parent.

You can grep for it; these are the devices that will begin to panic if
you apply this patch:

arch/ia64/hp/sim/simscsi.c:     error = scsi_add_host(host, NULL);
drivers/scsi/a2091.c:   error = scsi_add_host(instance, NULL);
drivers/scsi/a3000.c:   error = scsi_add_host(instance, NULL);
drivers/scsi/aha152x.c: if( scsi_add_host(shpnt, NULL) ) {
drivers/scsi/gdth.c:    error = scsi_add_host(shp, NULL);
drivers/scsi/gdth.c:    error = scsi_add_host(shp, NULL);
drivers/scsi/gvp11.c:   error = scsi_add_host(instance, NULL);
drivers/scsi/imm.c:     err = scsi_add_host(host, NULL);
drivers/scsi/pcmcia/fdomain_stub.c:    if (scsi_add_host(host, NULL))
drivers/scsi/pcmcia/nsp_cs.c:   ret = scsi_add_host (host, NULL);
drivers/scsi/pcmcia/qlogic_stub.c:      if (scsi_add_host(shost, NULL))
drivers/scsi/pcmcia/sym53c500_cs.c:     if (scsi_add_host(host, NULL))
drivers/scsi/ppa.c:     err = scsi_add_host(host, NULL);
drivers/scsi/qlogicfas.c:       if (scsi_add_host(hreg, NULL))
drivers/scsi/scsi_module.c:             error = scsi_add_host(shost, NULL);
drivers/scsi/sgiwd93.c: err = scsi_add_host(host, NULL);

Note I've picked up scsi_module, so anything that uses the SCSI module
interface also has this problem.

James