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firewire: ohci: fix compilation on arches without PAGE_KERNEL_RO

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PAGE_KERNEL_RO is not available on all architectures, so its use
in the new AR code broke compilation on sparc64.

Because the read-only mapping was just a debugging aid, just use
PAGE_KERNEL instead.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

James Bottomley wrote:
> On Thu, 2011-01-13 at 08:27 +0100, Clemens Ladisch wrote:
>> firewire: ohci: fix compilation on arches without PAGE_KERNEL_RO, e.g. sparc
>>
>> PAGE_KERNEL_RO is not available on all architectures, so its use in the
>> new AR code broke compilation on sparc64.
>>
>> Because the R/O mapping is only used to catch drivers that try to write
>> to the reception buffer and not actually required for correct operation,
>> we can just use a normal PAGE_KERNEL mapping where _RO is not available.
[...]
>> +/*
>> + * For archs where PAGE_KERNEL_RO is not supported;
>> + * mapping the AR buffers readonly for the CPU is just a debugging aid.
>> + */
>> +#ifndef PAGE_KERNEL_RO
>> +#define PAGE_KERNEL_RO PAGE_KERNEL
>> +#endif
>
> This might cause interesting issues on sparc64 if it ever acquired a
> PAGE_KERNEL_RO.  Sparc64 has extern pgprot_t for it's PAGE_KERNEL types
> rather than #defines, so the #ifdef check wouldn't see this.
>
> I think either PAGE_PROT_RO becomes part of our arch API (so all
> architectures are forced to add it), or, if it's not part of the API,
> ohci isn't entitled to use it.  The latter seems simplest since you have
> no real use for write protection anyway.

Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
This commit is contained in:
Clemens Ladisch 2011-01-13 10:12:17 +01:00 committed by Stefan Richter
parent 410cf2bd3d
commit 1427130425
1 changed files with 1 additions and 1 deletions
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2
drivers/firewire/ohci.c
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@ -961,7 +961,7 @@ static int ar_context_init(struct ar_context *ctx, struct fw_ohci *ohci,
for (i = 0; i < AR_WRAPAROUND_PAGES; i++)
pages[AR_BUFFERS + i] = ctx->pages[i];
ctx->buffer = vm_map_ram(pages, AR_BUFFERS + AR_WRAPAROUND_PAGES,
-1, PAGE_KERNEL_RO);
-1, PAGE_KERNEL);
if (!ctx->buffer)
goto out_of_memory;