[U-Boot] [PATCH] sunxi: use CONFIG_DEFAULT_FDT_FILE everywhere

[Maxime Ripard]

On Fri, Jun 01, 2018 at 10:16:32AM -0700, Martin Kelly wrote:
> On 06/01/2018 04:05 AM, Maxime Ripard wrote:
> > On Thu, May 31, 2018 at 05:59:16PM -0700, Martin Kelly wrote:
> > > Currently, sunxi-common.h ignores CONFIG_DEFAULT_FDT_FILE and assumes
> > > the kernel fdtfile and the u-boot devicetree names are the same.
> > > Although this is typically the case, sometimes you might want to
> > > customize one of these differently, so it's useful to allow them to be
> > > different.
> > > 
> > > Fix this to use only CONFIG_DEFAULT_FDT_FILE as other boards do, and set
> > > CONFIG_DEFAULT_FDT_FILE in board files to be the same as the current
> > > fdtfile= setting.
> > > 
> > > Signed-off-by: Martin Kelly <mkelly at xevo.com>
> > 
> > I'd really prefer not to do that. There's going to be a long trail of
> > defconfig that will be sent at pretty much the same time that are not
> > going to have it and that will go unnotice for some time.
> > 
> > And there's obviously the useless churn in all the defconfig that are
> > not in the case where it makes sense to override DEFAULT_FDT_FILE.
> > 
> > Why not create a Kconfig boolean that allows to select whether or not
> > you want DEFAULT_FDT_FILE to be DEFAULT_DEVICE_TREE + .dtb or a custom
> > value.
> 
> I can see the issues with new defconfigs, but I'm not sure if it will really
> be that bad. If we apply this patch against sunxi master, then shouldn't new
> patches get tested and rebased against it? In that case, if they have not
> set DEFAULT_FDT_FILE, it will default to "", the boards won't boot, and the
> mistake must be fixed prior to merging.

Unless one has tested it with a version prior to your patch, and sends
it. Not a lot of people are testing with the next branch in the
various trees.

> Alternatively if we add the Kconfig boolean, we need to worry about what
> happens when people have DEFAULT_FDT_FILE set already. I guess we would need
> to default the new Kconfig boolean to be custom in order to keep those
> configs from breaking. But if we do that, sunxi will break by default (since
> sunxi configs don't have the value set).
>
> What would you suggest the default value of the new boolean to be?

config DEFAULT_FDT_FILE_USE_DEFAULT_DEVICE_TREE
	bool "whatever"
	default y if ARCH_ROCKCHIP
	default y if ARCH_SUNXI

and in the headers

#ifdef CONFIG_DEFAULT_FDT_FILE_USE_DEFAULT_DEVICE_TREE
#define CONFIG_DEFAULT_FDT_FILE CONFIG_DEFAULT_DEVICE_TREE ".dtb"
#endif

And that's done.

> Personally, though I think it could be a bit painful through the next merge
> window, I think fixing this to operate the same way as the rest of the
> boards is the right long-term decision.

So far, I've seen two platforms using this, the two representing a
significant part of the total defconfig number, using the exact same
value for both. Surely that means there's room for improvement.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com
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