netdev - Re: [PATCH] [Rev2] MPC5121 FEC support

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Date:	Tue, 17 Jun 2008 23:00:55 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Scott Wood <scottwood@...escale.com>
Cc:	John Rigby <jrigby@...escale.com>, linuxppc-dev@...abs.org,
	jeff@...zik.org, netdev@...r.kernel.org
Subject: Re: [PATCH] [Rev2] MPC5121 FEC support

On Tue, Jun 17, 2008 at 03:03:54PM -0500, Scott Wood wrote:
> Sam Ravnborg wrote:
> >On Tue, Jun 17, 2008 at 02:33:28PM -0500, Scott Wood wrote:
> >>John Rigby wrote:
> >>>config FS_ENET
> >>>       tristate "Freescale Ethernet Driver"
> >>>-       depends on CPM1 || CPM2
> >>>+       depends on CPM1 || CPM2 || FS_ENET_MPC5121_FEC
> >>>       select MII
> >>>       select PHYLIB
> >>>
> >>>+config FS_ENET_MPC5121_FEC
> >>>+	bool "Freescale MPC512x FEC driver"
> >>>+	depends on PPC_MPC512x
> >>>+	select FS_ENET
> >>>+	select PPC_CPM_NEW_BINDING
> >>>+	default y
> >>No default y.
> >I by the way do not see the need for the prompt of FS_ENET.
> 
> Agreed, especially since it's overly broad (there is Freescale ethernet 
> hardware that this driver doesn't support).  We'd need to change depends 
> into selects in the more specific entries.
> 
> >Do you ever want to change it if one of the dependencies
> >are selected?
> 
> Do you mean if CPM1 or CPM2 is selected?  Yes, it's quite possible that 
> the user has no need for the CPM ethernet and would rather reclaim the 
> memory (especially on CPM1, which has boards as small as 8MiB).

I took a closer look now.
And I can see that FS_ENET is indeed a driver and CPM1, CPM2,  FS_ENET_MPC5121_FEC
are all booleans that say that it may make sense to use this driver.

But I was misguided by:
>+config FS_ENET_MPC5121_FEC
>+  select FS_ENET
This is not good.

In general when you select a symbol that has dependencies you are almost
always on the wrong track.
Use a dependency here with a sane default - then people can 
set it to 'n' if they really do not want this driver.

Spreading selects too much is just causing you pain in the long run.

	Sam
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