netdev - Re: [PATCH] CAN: Add Flexcan CAN controller driver

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Message-ID: <4C4C2782.9030204@pengutronix.de>
Date:	Sun, 25 Jul 2010 14:01:06 +0200
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Oliver Hartkopp <socketcan@...tkopp.net>
CC:	wg@...ndegger.com, socketcan-core@...ts.berlios.de,
	netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH] CAN: Add Flexcan CAN controller driver

Oliver Hartkopp wrote:
> first of all thanks for your contribution of the flexcan driver!

You're welcome!

> But i have a question regarding the Kconfig change that has been finally
> committed to net-next-2.6.

> It looks like the pulled code has some extra HAVE_CAN_FLEXCAN config option -
> which may be something of your debugging environment - which was not part of
> the original posted patch, where CAN_FLEXCAN depended on (ARCH_MX25 || ARCH_MX35).

Indeed this was not in the patch that Wolfgang Acked.

However, after Wolfgang's Ack I discussed the arm patches with the imx
people. I switched to dynamically registered devies, which is a more
modern way of registering them. And this led to the
"IMX_HAVE_PLATFORM_FLEXCAN" symbol (see below) and then we thought a
platform independent "HAVE_CAN_FLEXCAN" is even better.

So this was intentional (and in the latest patch I posed with the final
pull request.)

> Please see the two posted sections below ...

> The depency of (ARCH_MX25 || ARCH_MX35) makes more sense to me ;-)

The idea behind the "HAVE_CAN_FLEXCAN" is that all architectures select
this symbol if they have a flexcan core (which is supported by this
driver). On the imx platform we make this even in finer granularity.

BTW: If we on ARM finally have OF tree support we can change this easily
without needing to go over the net-next-2.6 tree.

Have a look at the corresponding ARM commits:
http://git.pengutronix.de/?p=imx/linux-2.6.git;a=commit;h=d7aec06a0decceabde9d9be6957229485568964b
http://git.pengutronix.de/?p=imx/linux-2.6.git;a=commit;h=b5a326c8c0a01692e710fc6086ddf84128b7a7d3

Here in detail+
http://git.pengutronix.de/?p=imx/linux-2.6.git;a=blob;f=arch/arm/plat-mxc/devices/Kconfig;h=9ab784b776f9192a33feaff37ff21be99b0a3691;hb=d7aec06a0decceabde9d9be6957229485568964b
We define a symbol without a prompt "IMX_HAVE_PLATFORM_FLEXCAN" for the
imx arm platform. This symbol selects "HAVE_CAN_FLEXCAN".

http://git.pengutronix.de/?p=imx/linux-2.6.git;a=blob;f=arch/arm/plat-mxc/devices/platform-flexcan.c;h=5e97a01f14f3eb106750f00d8a0fffb66f2c9563;hb=d7aec06a0decceabde9d9be6957229485568964b
A selected "IMX_HAVE_PLATFORM_FLEXCAN" symbol activates some glue code
that's used to create the individual flexcan devices.

It's up to the individual board code to select the
"IMX_HAVE_PLATFORM_FLEXCAN" symbol. This patch adds the flexcan support
on the pcm043:
http://git.pengutronix.de/?p=imx/linux-2.6.git;a=blobdiff;f=arch/arm/mach-mx3/Kconfig;h=03563eb997c0f761ea7d7e14d155facfce880e03;hp=e063657e1bf4c3f3d56a67e70bc3f17b333cfb55;hb=b5a326c8c0a01692e710fc6086ddf84128b7a7d3;hpb=d7aec06a0decceabde9d9be6957229485568964b

I hope that answers you question,
Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |

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