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

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

[Ralf Baechle]

On Thu, Jun 23, 2011 at 12:53:36PM +0100, Martyn Welch wrote:

> On 23/06/11 12:45, Ralf Baechle wrote:
> > On architectures that don't define PAGE_KERNEL_NOCACHE, the Comedi driver turns
> > into tragedy:
> > 
> >   CC [M]  drivers/staging/comedi/drivers.o
> > drivers/staging/comedi/drivers.c: In function ‘comedi_buf_alloc’:
> > drivers/staging/comedi/drivers.c:505:41: error: ‘PAGE_KERNEL_NOCACHE’ undeclared (first use in this function)
> > drivers/staging/comedi/drivers.c:505:41: note: each undeclared identifier is rep orted only once for each function it appears in
> > make[3]: *** [drivers/staging/comedi/drivers.o] Error 1
> > 
> > Restrict the driver to only those architectures that define PAGE_KERNEL_NOCACHE.
> > 
> > PAGE_KERNEL_NOCACHE is a kludge - some system architectures such as SGI IP27
> > are even uable to offer uncached operation - at least in the way an unwitting
> > driver might assume.  I haven't looked in details how the driver is using
> > the area vmaped with PAGE_KERNEL_NOCACHE but maybe doing it XFS-style using
> > cached memory and the flush_kernel_vmap_range / invalidate_kernel_vmap_range
> > APIs in conjunction with the DMA API is a practical alternative.
> > 
> > Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
> > 
> >  drivers/staging/comedi/Kconfig |    1 +
> >  1 files changed, 1 insertions(+), 0 deletions(-)
> > 
> > diff --git a/drivers/staging/comedi/Kconfig b/drivers/staging/comedi/Kconfig
> > 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
> 
> I'm sure I got comedi to compile on a 32-bit PPC board not that long ago. Has
> something changed, or is this just not an exhaustive list?

(Adding the PPC folks to cc.)

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.

  Ralf

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

[Kumar Gala]

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

> On Thu, Jun 23, 2011 at 12:53:36PM +0100, Martyn Welch wrote:
>=20
>> On 23/06/11 12:45, Ralf Baechle wrote:
>>> On architectures that don't define PAGE_KERNEL_NOCACHE, the Comedi =
driver turns
>>> into tragedy:
>>>=20
>>>  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)
>>> drivers/staging/comedi/drivers.c:505:41: note: each undeclared =
identifier is rep orted only once for each function it appears in
>>> make[3]: *** [drivers/staging/comedi/drivers.o] Error 1
>>>=20
>>> Restrict the driver to only those architectures that define =
PAGE_KERNEL_NOCACHE.
>>>=20
>>> PAGE_KERNEL_NOCACHE is a kludge - some system architectures such as =
SGI IP27
>>> are even uable to offer uncached operation - at least in the way an =
unwitting
>>> driver might assume.  I haven't looked in details how the driver is =
using
>>> the area vmaped with PAGE_KERNEL_NOCACHE but maybe doing it =
XFS-style using
>>> cached memory and the flush_kernel_vmap_range / =
invalidate_kernel_vmap_range
>>> APIs in conjunction with the DMA API is a practical alternative.
>>>=20
>>> Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
>>>=20
>>> drivers/staging/comedi/Kconfig |    1 +
>>> 1 files changed, 1 insertions(+), 0 deletions(-)
>>>=20
>>> diff --git a/drivers/staging/comedi/Kconfig =
b/drivers/staging/comedi/Kconfig
>>> 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
>>=20
>> I'm sure I got comedi to compile on a 32-bit PPC board not that long =
ago. Has
>> something changed, or is this just not an exhaustive list?
>=20
> (Adding the PPC folks to cc.)
>=20
> 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=

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

[Martyn Welch]

On 23/06/11 13:02, Ralf Baechle wrote:
> On Thu, Jun 23, 2011 at 12:53:36PM +0100, Martyn Welch wrote:
> 
>> On 23/06/11 12:45, Ralf Baechle wrote:
>>> On architectures that don't define PAGE_KERNEL_NOCACHE, the Comedi driver turns
>>> into tragedy:
>>>
>>>   CC [M]  drivers/staging/comedi/drivers.o
>>> drivers/staging/comedi/drivers.c: In function ‘comedi_buf_alloc’:
>>> drivers/staging/comedi/drivers.c:505:41: error: ‘PAGE_KERNEL_NOCACHE’ undeclared (first use in this function)
>>> drivers/staging/comedi/drivers.c:505:41: note: each undeclared identifier is rep orted only once for each function it appears in
>>> make[3]: *** [drivers/staging/comedi/drivers.o] Error 1
>>>
>>> Restrict the driver to only those architectures that define PAGE_KERNEL_NOCACHE.
>>>
>>> PAGE_KERNEL_NOCACHE is a kludge - some system architectures such as SGI IP27
>>> are even uable to offer uncached operation - at least in the way an unwitting
>>> driver might assume.  I haven't looked in details how the driver is using
>>> the area vmaped with PAGE_KERNEL_NOCACHE but maybe doing it XFS-style using
>>> cached memory and the flush_kernel_vmap_range / invalidate_kernel_vmap_range
>>> APIs in conjunction with the DMA API is a practical alternative.
>>>
>>> Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
>>>
>>>  drivers/staging/comedi/Kconfig |    1 +
>>>  1 files changed, 1 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/staging/comedi/Kconfig b/drivers/staging/comedi/Kconfig
>>> 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
>>
>> I'm sure I got comedi to compile on a 32-bit PPC board not that long ago. Has
>> something changed, or is this just not an exhaustive list?
> 
> (Adding the PPC folks to cc.)
> 
> 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.

Ah, just found the tree looks like I had a little patch to make it seemingly
work, though it will make it "not work" for most other archs at a guess (it
may not even be right on PPC):

diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c
index 44d6b62..263ad3d 100644
--- a/drivers/staging/comedi/drivers.c
+++ b/drivers/staging/comedi/drivers.c
@@ -505,7 +505,7 @@ int comedi_buf_alloc(struct comedi_device *dev, struct
comedi_subdevice *s,
                }
                if (i == n_pages) {
                        async->prealloc_buf =
-                           vmap(pages, n_pages, VM_MAP, PAGE_KERNEL_NOCACHE);
+                           vmap(pages, n_pages, VM_MAP, PAGE_KERNEL_NC);
                }
                vfree(pages);

(Sorry for the wrapping)

-- 
Martyn Welch (Principal Software Engineer) | Registered in England and
GE Intelligent Platforms                   | Wales (3828642) at 100
T +44(0)127322748                          | Barbirolli Square, Manchester,
E martyn.welch@ge.com                      | M2 3AB  VAT:GB 927559189

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

[Benjamin Herrenschmidt]

On Thu, 2011-06-23 at 13:02 +0100, Ralf Baechle wrote:
> On Thu, Jun 23, 2011 at 12:53:36PM +0100, Martyn Welch wrote:
> 
> > On 23/06/11 12:45, Ralf Baechle wrote:
> > > On architectures that don't define PAGE_KERNEL_NOCACHE, the Comedi driver turns
> > > into tragedy:
> > > 
> > >   CC [M]  drivers/staging/comedi/drivers.o
> > > drivers/staging/comedi/drivers.c: In function ‘comedi_buf_alloc’:
> > > drivers/staging/comedi/drivers.c:505:41: error: ‘PAGE_KERNEL_NOCACHE’ undeclared (first use in this function)
> > > drivers/staging/comedi/drivers.c:505:41: note: each undeclared identifier is rep orted only once for each function it appears in
> > > make[3]: *** [drivers/staging/comedi/drivers.o] Error 1
> > > 
> > > Restrict the driver to only those architectures that define PAGE_KERNEL_NOCACHE.
> > > 
> > > PAGE_KERNEL_NOCACHE is a kludge - some system architectures such as SGI IP27
> > > are even uable to offer uncached operation - at least in the way an unwitting
> > > driver might assume.  I haven't looked in details how the driver is using
> > > the area vmaped with PAGE_KERNEL_NOCACHE but maybe doing it XFS-style using
> > > cached memory and the flush_kernel_vmap_range / invalidate_kernel_vmap_range
> > > APIs in conjunction with the DMA API is a practical alternative.
> > > 
> > > Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
> > > 
> > >  drivers/staging/comedi/Kconfig |    1 +
> > >  1 files changed, 1 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/drivers/staging/comedi/Kconfig b/drivers/staging/comedi/Kconfig
> > > 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
> > 
> > I'm sure I got comedi to compile on a 32-bit PPC board not that long ago. Has
> > something changed, or is this just not an exhaustive list?

It went away. There's a proper API (pgprot_noncached), but it depends
what this is used for and it's likely to be broken anyways... what is
that driver trying to map non-cached ?

Cheers,
Ben.

> (Adding the PPC folks to cc.)
> 
> 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.
> 
>   Ralf
> --
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