linux-kernel - Re: [PATCH 1/3] mfd: add support for Janz CMOD-IO PCI MODULbus Carrier Board

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Date:	Thu, 25 Mar 2010 23:59:30 +0100
From:	Samuel Ortiz <sameo@...ux.intel.com>
To:	"Ira W. Snyder" <iws@...o.caltech.edu>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	socketcan-core@...ts.berlios.de
Subject: Re: [PATCH 1/3] mfd: add support for Janz CMOD-IO PCI MODULbus
 Carrier Board

Hi Ira,

First of all, sorry for the late reply. Then my answers:

On Fri, Mar 19, 2010 at 11:22:09AM -0700, Ira W. Snyder wrote:
> 
> > > +/*
> > > + * Subdevice Support
> > > + */
> > Please use the mfd-core API for building and registering platform sub devices.
> > The pieces of code below should shrink significantly.
> > 
> 
> Using this framework, how is it possible to create  the devices that I
> do down below. For each subdevice, I need three resources:
> 
> 1) MODULbus registers -- PCI BAR3 + (0x200 * module_num)
> 2) PLX Control Registers -- PCI BAR4
> 3) IRQ
> 
> Specifically, the way IORESOURCE_MEM resources are copied seems wrong.
> They start at the base address of only one resource and use the offsets
> provided in the struct mfd_cell. See the if-statement at
> drivers/mfd/mfd-core.c line 48.
> 
> I need two use two different parent resources. The mfd_add_devices()
> function doesn't support this.
I would still like you to use the mfd-core API. Here is my proposal:

1) I modify mfd_add_device() to support a NULL mem_base argument. When
mem_base is NULL, we would have:

res[r].parent = NULL and res[r].start = cell->resources[r].start;

The platform code will use iomem_resource as the parent for this resource.

2) Your mfd_cell cells would have 3 resources, and you just need to set the
IORESOURCE_MEM ones at probe time, with pci->resource[n]->start + offset as
the start field.

Would that make sense to you ?

> > > +	/* Onboard configuration registers */
> > > +	priv->ctrl = pci_ioremap_bar(dev, 4);
> > Why 4 ?
> > 
> > 
> 
> Because that is how the device works ;) There is a comment up above that
> describes them as the "PLX control registers". Are you suggesting that I
> add a comment here too?
No, that's ok, I missed the comment.

> > > +#define PCI_VENDOR_ID_JANZ		0x13c3
> > That probably belongs to pci_ids.h
> > 
> 
> Should I add a patch to the series for this?
Either that or merge the pci_ids.h changes with this patch.

Cheers,
Samuel.
 
-- 
Intel Open Source Technology Centre
http://oss.intel.com/
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