linux-kernel - Re: [PATCH 03/12] nvmem: mtk-efuse: fix different address space warnings of sparse

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Date:   Fri, 20 Oct 2017 22:55:04 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/12] nvmem: mtk-efuse: fix different address space
 warnings of sparse

2017-10-20 22:34 GMT+09:00 Greg KH <gregkh@...uxfoundation.org>:
> On Mon, Oct 09, 2017 at 03:26:32PM +0200, srinivas.kandagatla@...aro.org wrote:
>> From: Masahiro Yamada <yamada.masahiro@...ionext.com>
>>
>> Fix the following sparse warnings:
>>
>> drivers/nvmem/mtk-efuse.c:24:30: warning: incorrect type in initializer (different address spaces)
>> drivers/nvmem/mtk-efuse.c:24:30:    expected void [noderef] <asn:2>*base
>> drivers/nvmem/mtk-efuse.c:24:30:    got void *context
>> drivers/nvmem/mtk-efuse.c:37:30: warning: incorrect type in initializer (different address spaces)
>> drivers/nvmem/mtk-efuse.c:37:30:    expected void [noderef] <asn:2>*base
>> drivers/nvmem/mtk-efuse.c:37:30:    got void *context
>> drivers/nvmem/mtk-efuse.c:69:23: warning: incorrect type in assignment (different address spaces)
>> drivers/nvmem/mtk-efuse.c:69:23:    expected void *priv
>> drivers/nvmem/mtk-efuse.c:69:23:    got void [noderef] <asn:2>*[assigned] base
>>
>> The type of nvmem_config->priv is (void *), so sparse complains
>> about assignment of the base address with (void __iomem *) type.
>>
>> Even if we cast it out, sparse still warns:
>> warning: cast removes address space of expression
>>
>> Of course, we can shut up the sparse by marking __force, but a more
>> correct way is to put the base address into driver private data.
>
> Ick, no, really?
>
> That's horrid.  Do the __force cast as that is what you are really doing
> here, and it is good to see the bad use of it (hint, perhaps the api
> needs to be fixed up so you do not have to do that???)


Other drivers take private data from the "void *context".

In this driver, the priv just happens to have one member.
What's the matter?




>> diff --git a/drivers/nvmem/mtk-efuse.c b/drivers/nvmem/mtk-efuse.c
>> index fa7a0f66b37e..c4058b598703 100644
>> --- a/drivers/nvmem/mtk-efuse.c
>> +++ b/drivers/nvmem/mtk-efuse.c
>> @@ -18,15 +18,19 @@
>>  #include <linux/nvmem-provider.h>
>>  #include <linux/platform_device.h>
>>
>> +struct mtk_efuse_priv {
>> +     void __iomem *base;
>> +};
>> +
>>  static int mtk_reg_read(void *context,
>
>
> Make the read call take a __iomem *, not a random void *.  That should
> solve this issue, right?
>

NACK.

See drivers/nvmem/imx-iim.c

The ->reg_read hook needs more private data than __iomem *.



-- 
Best Regards
Masahiro Yamada