Re: [PATCH] ibmvscsi driver - sixth version

From: Dave Boutcher
Date: Wed Mar 31 2004 - 18:54:18 EST

On 31 Mar 2004 18:39:57 -0500, James Bottomley <James.Bottomley@xxxxxxxxxxxx> wrote:
> 14) why are you faking a PCI bus? The following is very, very wrong:
> +static struct pci_dev iseries_vscsi_dev = {
> + .dev.bus = &pci_bus_type,
> + .dev.bus_id = "vscsi",
> + .dev.release = noop_release
> Did I mention "very" wrong? :)
Because for iseries it is implemented in the pci code. While it may
look wrong, it is actually correct. Check out
arch/ppc64/kernel/iSeries_iommu.c and arch/ppc64/kernel/dma.c.
This device has to have dev->bus == &pci_bus_type otherwise the
dma_mapping_foo functions won't work correctly.

Erm, something is very wrong in the iSeries code then. This
iseries_vio_device is a struct device. As such, it should contain all
the information it needs for the DMA API to act on it without performing
silly pci device tricks.

This looks like it's done because the iseries should be converted to the
generic device infrastructure, but in fact it's not. Since the generic
API has been around for over a year and was designed to solve precisely
these very problems it needs fixing rather than trying to work around it
in a driver.
There will always be 1 (no more, no less) of these struct devices in the
system, so I'll move the definition of this into iSeries_iommu and then
just reference it from the driver. I think that should abstract things

Dave B
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