linux-kernel - Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast removes address space '_

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Message-ID: <20201112092715.7e466405@xps13>
Date:   Thu, 12 Nov 2020 09:27:15 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Serge Semin <fancer.lancer@...il.com>,
        kernel test robot <lkp@...el.com>, <kbuild-all@...ts.01.org>,
        <linux-kernel@...r.kernel.org>, <linux-mtd@...ts.infradead.org>
Subject: Re: drivers/mtd/maps/physmap-bt1-rom.c:78:18: sparse: sparse: cast
 removes address space '__iomem' of expression

Hi Sergey,

Serge Semin <Sergey.Semin@...kalelectronics.ru> wrote on Wed, 11 Nov
2020 22:22:59 +0300:

> On Tue, Nov 10, 2020 at 04:35:56PM +0100, Miquel Raynal wrote:
> > Hi Serge,
> > 
> > Serge Semin <Sergey.Semin@...kalelectronics.ru> wrote on Tue, 10 Nov
> > 2020 14:38:27 +0300:
> >   
> > > Hello Miquel,
> > > 
> > > A situation noted by the warning below won't cause any problem because
> > > the casting is done to a non-dereferenced variable. It is utilized
> > > as a pointer bias later in that function. Shall we just ignore the
> > > warning or still fix it somehow?  
> >   
> 
> > Do you think the cast to a !__iomem value is mandatory here?  
> 
> It's not mandatory to have the casting with no __iomem, but wouldn't
> doing like this:
> + 	shift = (ssize_t __iomem)src & 0x3;
> be looking weird? Really, is there a good way to somehow extract the first
> two bits of a __iomem pointer without getting the sparse warning?

I asked around me, what about trying uintptr_t?

Thanks,
Miquèl