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.
>>
>> Thanks to Stefan Richter and Marc Gauthier <marc@xxxxxxxxxxxxx> for
>> suggesting this fix.
>>
>> Signed-off-by: Clemens Ladisch <clemens@xxxxxxxxxx>
>>
>> --- a/drivers/firewire/ohci.c
>> +++ b/drivers/firewire/ohci.c
>> @@ -91,6 +91,14 @@ struct descriptor {
>> #define MAX_AR_PACKET_SIZE (16 + MAX_ASYNC_PAYLOAD + 4)
>> #define AR_WRAPAROUND_PAGES DIV_ROUND_UP(MAX_AR_PACKET_SIZE, PAGE_SIZE)
>>
>> +/*
>> + * 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.
--8<---------------------------------------------------------------->8--
firewire: ohci: fix compilation on arches without PAGE_KERNEL_RO
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@xxxxxxxxxx>
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -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;
--
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