Re: [PATCH] RISC-V: io: Don't have a void* PCI_IOBASE

From: Andreas Schwab <schwab@suse.de>
To: Palmer Dabbelt <palmer@rivosinc.com>
Cc: linux-riscv@lists.infradead.org
Subject: Re: [PATCH] RISC-V: io: Don't have a void* PCI_IOBASE
Date: Mon, 27 May 2024 09:44:13 +0200	[thread overview]
Message-ID: <mvm5xuzwvg2.fsf@suse.de> (raw)
In-Reply-To: <20240526213617.12890-2-palmer@rivosinc.com> (Palmer Dabbelt's message of "Sun, 26 May 2024 14:36:18 -0700")

On Mai 26 2024, Palmer Dabbelt wrote:

> I recently started noticing warnings along the lines of
>
>     include/asm-generic/io.h:752:2: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>             insw(addr, buffer, count);
>             ^~~~~~~~~~~~~~~~~~~~~~~~~
>     arch/riscv/include/asm/io.h:105:53: note: expanded from macro 'insw'
>     #define insw(addr, buffer, count) __insw(PCI_IOBASE + (addr), buffer, count)
>
> which are triggered by having PCI_IOBASE be a "void __iomem *".  I'm not
> quite sure what the right thing to do is here: having it as u8 to make
> the pointer arithmetic work seems reasonable to me,

A u8 null pointer is still a null pointer.  Are you sure you are quoting
the right warning?  AFAICS, PCI_IOBASE is not a null pointer.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
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