From: Michael Ellerman <mpe@ellerman•id.au>
To: Linus Walleij <linus.walleij@linaro•org>,
Nicholas Piggin <npiggin@gmail•com>,
Christophe Leroy <christophe.leroy@csgroup•eu>
Cc: Linus Walleij <linus.walleij@linaro•org>,
linuxppc-dev@lists•ozlabs.org, linux-kernel@vger•kernel.org,
kernel test robot <lkp@intel•com>
Subject: Re: [PATCH] powerpc: Fix signature of pfn_to_kaddr()
Date: Tue, 07 Nov 2023 16:57:40 +1100 [thread overview]
Message-ID: <87ttpyw1ez.fsf@mail.lhotse> (raw)
In-Reply-To: <20231106-virt-to-pfn-fix-ppc-v1-1-93197a7ccab4@linaro.org>
Linus Walleij <linus.walleij@linaro•org> writes:
> There is a const in the returned value from pfn_to_kaddr()
> but there are consumers that want to modify the result
> and the generic function pfn_to_virt() in <asm-generic/page.h>
> does allow this, so let's relax this requirement and do not
> make the returned value const.
>
> Reported-by: kernel test robot <lkp@intel•com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202311061940.4pBrm44u-lkp@intel.com/
I'm struggling to connect the removal of const with those bug reports.
It looks like all those warnings are about 0xc000000000000000 being
outside the range of unsigned long when building 32-bit.
Is it the right bug report link?
The current signature of:
static inline const void *pfn_to_kaddr(unsigned long pfn) ...
seems OK to me.
It allows code like:
const void *p = pfn_to_kaddr(pfn);
p++;
But errors for:
const void *p = pfn_to_kaddr(pfn);
unsigned long *q = p;
*q = 0;
error: initialization discards ‘const’ qualifier from pointer target type
Having said that it looks like almost every caller of pfn_to_kaddr()
casts the result to unsigned long, so possibly that would be the better
return type in terms of the actual usage. Although that would conflict
with __va() which returns void * :/
cheers
next prev parent reply other threads:[~2023-11-07 5:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-06 13:44 [PATCH] powerpc: Fix signature of pfn_to_kaddr() Linus Walleij
2023-11-07 5:57 ` Michael Ellerman [this message]
2023-11-07 8:06 ` Linus Walleij
2023-11-10 6:16 ` Michael Ellerman
2023-11-08 19:24 ` Christophe Leroy
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