linux-kernel - Re: [PATCH v2] mmc: mmci_qcom_dml: include mmci_qcom

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Date:   Sun, 6 Aug 2017 11:32:41 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-mmc <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>
Subject: Re: [PATCH v2] mmc: mmci_qcom_dml: include mmci_qcom_dml.h and fix #ifdef

On Sun, Aug 6, 2017 at 4:58 AM, Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
> 2017-08-05 7:10 GMT+09:00 Arnd Bergmann <arnd@...db.de>:
>> On Fri, Aug 4, 2017 at 3:34 PM, Masahiro Yamada
>> <yamada.masahiro@...ionext.com> wrote:
>>> Include mmci_qcom_dml.h from mmci_qcom_dml.c to fix the following
>>> sparse warnings:
>>>
>>>   CHECK   drivers/mmc/host/mmci_qcom_dml.c
>>> drivers/mmc/host/mmci_qcom_dml.c:57:6: warning: symbol 'dml_start_xfer' was not declared. Should it be static?
>>> drivers/mmc/host/mmci_qcom_dml.c:122:5: warning: symbol 'dml_hw_init' was not declared. Should it be static?
>>>
>>> Fixing them causes redefintion of dml_start_xfer error, revealing another
>>> problem in the header.  #ifdef CONFIG_MMC_QCOM_DML is wrong because this
>>> driver is tristate.  (CONFIG_MMC_QCOM_DML_MODULE is defined when it is
>>> built as a module)
>>>
>>> Since dml_hw_init() is called from mmci.c, IS_REACHABLE() is needed to
>>> cater to all the combinations.
>>>
>>> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
>>
>> I think this is still not a good solution, it will just turn a link error into
>> an unusable system at runtime when the DML code is a loadable module
>> but not used. Also, the symbols are not exported, so it won't work when both
>> are built as modules.
>> How about linking the DML code into the mmci module and making that
>> Kconfig option a 'bool'?
>
>
> You are right.
> My patch does not solve the root of the problem.
>
> It turned out not so trivial as I had first expected.
>
> I'd like somebody else to take care of it
> because I am not familiar with this driver.

Maybe it's best if Ulf just reverts the broken commit, and then we start
over with reviewing the patch properly.

         Arnd