linux-kernel - Re: [PATCH 1/2] dmaengine: sh: Do not enable SH_DMAE

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Message-ID: <99ca93ef-ab26-4d6b-bc7b-fd2f98aecabe@linaro.org>
Date: Tue, 8 Jul 2025 15:21:40 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Vinod Koul <vkoul@...nel.org>, Peter Ujfalusi <peter.ujfalusi@...il.com>,
 dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
 Linux-sh list <linux-sh@...r.kernel.org>
Subject: Re: [PATCH 1/2] dmaengine: sh: Do not enable SH_DMAE_BASE by default
 during compile testing

On 08/07/2025 15:07, Geert Uytterhoeven wrote:
> CC linux-sh
> 
> Hi Krzysztof,
> 
> On Fri, 4 Apr 2025 at 14:22, Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org> wrote:
>> Enabling the compile test should not cause automatic enabling of all
>> drivers.
>>
>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> 
> Thanks for your patch, which is now commit 587dd30449fb1012
> ("dmaengine: sh: Do not enable SH_DMAE_BASE by default during
> compile testing") in dmaengine/next.
> 
>> --- a/drivers/dma/sh/Kconfig
>> +++ b/drivers/dma/sh/Kconfig
>> @@ -16,7 +16,7 @@ config SH_DMAE_BASE
>>         depends on SUPERH || COMPILE_TEST
>>         depends on !SUPERH || SH_DMA
>>         depends on !SH_DMA_API
>> -       default y
>> +       default SUPERH || SH_DMA
> 
> I think the check for SUPERH is superfluous, due to the dependency on
> "!SUPERH || SH_DMA" above.
> 

Indeed it might be, but I must admit I don't understand the dependencies
here at all. I think commit 9f2c2bb31258 ("dmaengine: sh: Rework Kconfig
and Makefile") from Laurent made it confusing and this later just grew
to even more confusing.

What is the intention for "depends on"? This should be enabled when
SUPERH AND SH_DMA are enabled?

SH_DMA cannot be enabled without SUPERH (no compile test), right? But
this "depends on !SUPERH || SH_DMA" suggests it could be. This should be
read for humans as "if not SUPERH, then require at least SH_DMA".
Otherwise what is the meaning for humans? This driver will work fine
without SUERPH?

My change for default could be rewritten but I don't understand the goal
behind current depends, so not sure how should I rewrite it.

Best regards,
Krzysztof