linux-kernel - Re: [PATCH] [RFC v3] OF: OpenFirmware bindings for the mmc

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Message-ID: <fa686aa40806051142q61ba471fl772ed32586b70e5c@mail.gmail.com>
Date:	Thu, 5 Jun 2008 12:42:49 -0600
From:	"Grant Likely" <grant.likely@...retlab.ca>
To:	avorontsov@...mvista.com
Cc:	"Pierre Ossman" <drzeus-mmc@...eus.cx>,
	"David Brownell" <dbrownell@...rs.sourceforge.net>,
	"Jochen Friedrich" <jochen@...am.de>,
	"Segher Boessenkool" <segher@...nel.crashing.org>,
	"Gary Jennejohn" <garyj@...x.de>,
	"Guennadi Liakhovetski" <g.liakhovetski@....de>,
	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [RFC v3] OF: OpenFirmware bindings for the mmc_spi driver

On Thu, Jun 5, 2008 at 12:31 PM, Anton Vorontsov
<avorontsov@...mvista.com> wrote:
> On Thu, Jun 05, 2008 at 12:18:56PM -0600, Grant Likely wrote:
>> On Thu, Jun 5, 2008 at 12:00 PM, Anton Vorontsov
>> <avorontsov@...mvista.com> wrote:
>> > On Thu, Jun 05, 2008 at 11:36:09AM -0600, Grant Likely wrote:
>> >> On Thu, Jun 5, 2008 at 11:27 AM, Anton Vorontsov
>> >> <avorontsov@...mvista.com> wrote:
>> >> > Well, I mentioned the usb_add_hcd()-alike approach for the mmc_spi
>> >> > host... The absence of enthusiasm I equaled to "no".
>> >> >
>> >> > Heh.
>> >>
>> >> I'm allergic to USB HCD code; I was probably having convulsions under my desk.
>> >
>> > :-)
>> >
>> > Ok, I also mentioned drivers/ata/pata_of_platform.c (OF version is using
>> > common code from drivers/ata/pata_platform.c).
>> >
>> > Please look there, and tell me if this is what you have in mind. (ignore
>> > _probe in the __pata_platform_probe name. Imagine
>> > pata_platform_add_controller or something).
>>
>> Yes, I like that.  I've done something very similar for drivers with
>> both of and non-of bindings.  For another example, this time all
>> contained within a single .c file, see drivers/video/xilinxfb.c
>
> Ok, great. As I said previously, this is quite easy to do.
>
>> >> > p.s.
>> >> > Btw, you forgot another downside of v2 approach: struct spi_driver
>> >> > duplication... Not sure if everyone will be happy about it.
>> >> >
>> >> > Though, v2 is only version where we can make modular OF_MMC_SPI.
>> >>
>> >> I think we've got our wires crossed.  I'm not referring to the option
>> >> of an of_mmc_spi driver registering an mmc_spi device (which can then
>> >> be probed by the mmc_spi_driver).
>> >
>> > I'm not refrering to this option either.
>>
>> Okay, I'm confused then.  Where is the duplication of struct spi_driver?
>
> Here it is http://lkml.org/lkml/2008/5/23/299
> + static struct spi_driver of_mmc_spi_driver = {

Right; I was going down the wrong thought path.  I have no problem with this.

BTW, while on that topic, I think it is reasonable to roll the members
of of_mmc_spi into either the mmc_spi_platform_data or the
mmc_spi_host structure.  It is just 2 integers and that would
eliminate storing driver data pointers in seemingly random places.

> And here http://lkml.org/lkml/2008/5/24/153 David Brownell says:
>> The only thing that looks odd to me about this is that the wrapper
>> is a spi_device rather than an of_device.  To me it makes more sense
>> to just have an of_device setting up the right spi_device.  (Though
>> maybe I missed some discussion about why that can't work.)

Yeah; I'm not fond of that approach.  It incurs runtime cost of
multiple 'struct device' for a single device which is unnecessary.

> I hope the bottom line is that we're now all happy to create another
> spi_driver to handle "OF MMC-o-SPI" devices..?

Yes, I'm cool with it.

Cheers,
g.

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