linux-kernel - Re: [PATCH 3/4] spi: Add OF binding support for SPI busses

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Date:	Fri, 16 May 2008 16:14:23 -0600
From:	"Grant Likely" <grant.likely@...retlab.ca>
To:	cbouatmailru@...il.com
Cc:	linuxppc-dev@...abs.org, spi-devel-general@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, dbrownell@...rs.sourceforge.net,
	fabrizio.garetto@...il.com
Subject: Re: [PATCH 3/4] spi: Add OF binding support for SPI busses

On Fri, May 16, 2008 at 4:03 PM, Anton Vorontsov <cbouatmailru@...il.com> wrote:
> On Fri, May 16, 2008 at 01:36:13PM -0600, Grant Likely wrote:
>> +             /* Store a pointer to the node in the device structure */
>> +             of_node_get(nc);
>> +             spi->dev.archdata.of_node = nc;
>> +
>> +             /* Register the new device */
>> +             rc = spi_register_device(spi);
>> +             if (rc) {
>> +                     dev_err(&master->dev, "spi_device register error %s\n",
>> +                             np->full_name);
>> +                     spi_device_release(spi);
>> +             }
>
> No way to pass platform data... can you suggest any idea to use
> this for things like
> "[POWERPC] 86xx: mpc8610_hpcd: add support for SPI and MMC-over-SPI"
> I've sent just recently...?

That's right.  platform_data being a very driver specific thing there
is no way to generically extract a pdata structure from the device
tree.  Instead, I'm storing the device node in archdata.of_node (line
immediately above spi_register_device) so that drivers can read the
device node themselves to populate a platform_device structure.
(Protected by CONFIG_OF of course).

> Maybe this code could do something like
> spi->dev.platform_data = nc->data;
> and board code would fill nc->data at early stages? This needs to be a
> convention, not just random use though.. Maybe we can expand the struct
> device_node to explicitly include .platform_data for such cases?

Hmmm, as you say, this could end up being rather messy.  However, by
passing the device node pointer, the driver could extract that data on
a per case basis.  (ie. it would be decided on a per driver basis
where to get the platform data).  I'm not sure; this bears more
thought...

Cheers,
g.

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
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