Re: [PATCH v4 08/10] arm: add QEMU, Rcar3 and MPSoC configs

From: Julien Grall <julien.grall@arm.com>
To: Stefano Stabellini <sstabellini@kernel.org>,
	Julien Grall <julien.grall@gmail.com>
Cc: artem_mygaiev@epam.com, lars.kurth@citrix.com,
	andrii_anisov@epam.com, xen-devel@lists.xen.org,
	dfaggioli@suse.com, volodymyr_babchuk@epam.com
Subject: Re: [PATCH v4 08/10] arm: add QEMU, Rcar3 and MPSoC configs
Date: Mon, 4 Jun 2018 16:58:55 +0100	[thread overview]
Message-ID: <30cba2b4-8663-5bdc-c0dd-77dec2441518@arm.com> (raw)
In-Reply-To: <alpine.DEB.2.10.1806010842320.23991@sstabellini-ThinkPad-X260>

On 06/01/2018 09:51 PM, Stefano Stabellini wrote:
> On Fri, 1 Jun 2018, Julien Grall wrote:
>> Hi Stefano,
>> Sorry for formatting.
>>
>> On Thu, 31 May 2018, 22:50 Stefano Stabellini, <sstabellini@kernel.org> wrote:
>>        Add a "Platform Support" menu with three umbrella kconfig options: QEMU,
>>        RCAR3 and MPSOC. They enable the required options for their hardware
>>        platform.
>>
>>
>> This patch is nothing close to what we discussed. As far as I can tell, the tiny.config will end up to select all the platforms
>> with their driver. It will not be possible to deselect the driver selected for a platform afterwards.
>>
>> I still think the best if providing a choice list where only one option can be selected. I would like to understand why you
>> didn't go this path.
> 
> Yes, sorry, I didn't explain why I did this and what I told you on the
> call was wrong, adding to the confusion.
> 
> First, it is true that `make olddefconfig' is run automatically on any
> make target.
> 
> Except for `make menuconfig', that's special. If you copy a partial
> config (like tiny.config) to .config, then execute `make menuconfig',
> the menu gets automatically populated with the missing values using
> defaults (as if olddefconfig was run), but it won't automatically save
> them to file (fortunately!!).  That means that all the platform options
> below (QEMU, RCAR3, MPSOC) will show as selected in the menu, but if the
> user deselects two of them, for instance QEMU and RCAR3, the result is
> that *only* MPSOC and related options will be written down to the
> .config.
> 
> The kconfig infrastructure is not as bad as I initially thought :-)
> In short, the following steps work:
> 
> - copy tiny.config to .config
> - make menuconfig -> deselect QEMU and RCAR3, save .config

IHMO, this is really fragile. As you said most of the command will run 
"make oldconfig" automatically. This is also quite natural for a Linux 
user to do a "make oldconfig" after copying the .config.

So I think we should be able to cater everyone here rather than one 
"odd" solution. You seem to have misunderstood my suggestion on previous 
version. I answered there and would appreciate if you have another look.

Cheers,

-- 
Julien Grall

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