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 16:49:11 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
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

On Fri, Oct 20, 2017 at 10:55:04PM +0900, Masahiro Yamada wrote:
> 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 *.

Ok, that makes a bit more sense, but it still feels a bit of a hack,
don't you agree?

thanks,

greg k-h