Re: [PATCH] STAGING: Comedi: Build only on arches providing PAGE_KERNEL_NOCACHE

On Jun 23, 2011, at 7:02 AM, Ralf Baechle wrote:

On Thu, Jun 23, 2011 at 12:53:36PM +0100, Martyn Welch wrote:
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On 23/06/11 12:45, Ralf Baechle wrote:

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On architectures that don't define PAGE_KERNEL_NOCACHE, the Comedi =

driver turns

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into tragedy:
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 CC [M]  drivers/staging/comedi/drivers.o
drivers/staging/comedi/drivers.c: In function =91comedi_buf_alloc=92:
drivers/staging/comedi/drivers.c:505:41: error: =

=91PAGE_KERNEL_NOCACHE=92 undeclared (first use in this function)

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drivers/staging/comedi/drivers.c:505:41: note: each undeclared =

identifier is rep orted only once for each function it appears in

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make[3]: *** [drivers/staging/comedi/drivers.o] Error 1
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Restrict the driver to only those architectures that define =

PAGE_KERNEL_NOCACHE.

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PAGE_KERNEL_NOCACHE is a kludge - some system architectures such as =

SGI IP27

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are even uable to offer uncached operation - at least in the way an =

unwitting

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driver might assume.  I haven't looked in details how the driver is =

using

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the area vmaped with PAGE_KERNEL_NOCACHE but maybe doing it =

XFS-style using

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cached memory and the flush_kernel_vmap_range / =

invalidate_kernel_vmap_range

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APIs in conjunction with the DMA API is a practical alternative.
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Signed-off-by: Ralf Baechle <redacted>
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drivers/staging/comedi/Kconfig |    1 +
1 files changed, 1 insertions(+), 0 deletions(-)
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diff --git a/drivers/staging/comedi/Kconfig =

b/drivers/staging/comedi/Kconfig

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index 1502d80..bccdc12 100644

--- a/drivers/staging/comedi/Kconfig
+++ b/drivers/staging/comedi/Kconfig

@@ -2,6 +2,7 @@ config COMEDI

	tristate "Data acquisition support (comedi)"
	default N
	depends on m
+	depends on BROKEN || FRV || M32R || MN10300 || SUPERH || TILE || =

X86

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I'm sure I got comedi to compile on a 32-bit PPC board not that long =

ago. Has

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something changed, or is this just not an exhaustive list?

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(Adding the PPC folks to cc.)
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A "git grep -w PAGE_KERNEL_NOCACHE arch/powerpc/" doesn't find =

anything so

I don't think the driver will build there.  I don't have a PPC =

toolchain

to verify that.

I can verify it fails on PPC as well:

drivers/staging/comedi/drivers.c: In function 'comedi_buf_alloc':
drivers/staging/comedi/drivers.c:505:37: error: 'PAGE_KERNEL_NOCACHE' =
undeclared (first use in this function)
drivers/staging/comedi/drivers.c:505:37: note: each undeclared =
identifier is reported only once for each function it appears in

However, we do have a #define for PAGE_KERNEL_NC.

- k=