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Subject[PATCH] x86/mm: Clean up types in xlate_dev_mem_ptr() some more

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> Ugh, I pulled, but:
>
> On Wed, May 6, 2015 at 5:58 AM, Ingo Molnar <mingo2.kernel.org@gmail.com> wrote:
> >
> > Ingo Molnar (1):
> > x86/mm: Clean up types in xlate_dev_mem_ptr()
> >
> > diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> > index fdf617c00e2f..4bf037b20f47 100644
> > --- a/arch/x86/mm/ioremap.c
> > +++ b/arch/x86/mm/ioremap.c
> > @@ -332,18 +332,20 @@ EXPORT_SYMBOL(iounmap);
> > */
> > void *xlate_dev_mem_ptr(phys_addr_t phys)
> > {
> > + unsigned long start = phys & PAGE_MASK;
> > + unsigned long offset = phys & ~PAGE_MASK;
> > + unsigned long vaddr;
>
> That "unsigned long vaddr" is just stupid and not a cleanup.
>
> It causes two pointless casts:
>
> > + vaddr = (unsigned long)ioremap_cache(start, PAGE_SIZE);
> > + /* Only add the offset on success and return NULL if the ioremap() failed: */
> > + if (vaddr)
> > + vaddr += offset;
> >
> > + return (void *)vaddr;
>
> neither of which is helpful in the least. And the "vaddr += offset"
> would work equally well in "void *", gcc is perfectly happy to treat
> "void *" arithmetic as byte offsets, it's both documented and
> already extensively used in the kernel.

Yeah, not sure why I didn't notice that, I love void * arithmetics.

> So the cleanup to use "start/offset" is a good cleanup, but you
> should have kept "addr" as a pointer.

Something like the patch below?

Thanks,

Ingo

===================>
From 562bfca4c80175d1d18eef5c3f4bb8dda53c03e4 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@kernel.org>
Date: Fri, 8 May 2015 12:43:53 +0200
Subject: [PATCH] x86/mm: Clean up types in xlate_dev_mem_ptr() some more

So Linus noticed that in:

94d4b4765b7d ("x86/mm: Clean up types in xlate_dev_mem_ptr()")

... I added two nonsensical casts, due to the poor type choice
for 'vaddr'.

Change it to 'void *' and take advantage of void * arithmetics.

This removes the casts.

( Also remove a nonsensical return line from unxlate_dev_mem_ptr()
while at it. )

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/mm/ioremap.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 70e7444c6835..27ff21216dfa 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -353,18 +353,18 @@ void *xlate_dev_mem_ptr(phys_addr_t phys)
{
unsigned long start = phys & PAGE_MASK;
unsigned long offset = phys & ~PAGE_MASK;
- unsigned long vaddr;
+ void *vaddr;

/* If page is RAM, we can use __va. Otherwise ioremap and unmap. */
if (page_is_ram(start >> PAGE_SHIFT))
return __va(phys);

- vaddr = (unsigned long)ioremap_cache(start, PAGE_SIZE);
+ vaddr = ioremap_cache(start, PAGE_SIZE);
/* Only add the offset on success and return NULL if the ioremap() failed: */
if (vaddr)
vaddr += offset;

- return (void *)vaddr;
+ return vaddr;
}

void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
@@ -373,7 +373,6 @@ void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
return;

iounmap((void __iomem *)((unsigned long)addr & PAGE_MASK));
- return;
}

static pte_t bm_pte[PAGE_SIZE/sizeof(pte_t)] __page_aligned_bss;

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