[PATCH RFT] c6x: dma-mapping: support debug_dma_mapping_error

[PATCH RFT] c6x: dma-mapping: support debug_dma_mapping_error

[Shuah Khan]

Add support for debug_dma_mapping_error() call to avoid warning from
debug_dma_unmap() interface when it checks for mapping error checked
status. Without this patch, device driver failed to check map error
warning is generated.

Signed-off-by: Shuah Khan <shuah.khan@hp.com>
---
 arch/c6x/include/asm/dma-mapping.h |    1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/c6x/include/asm/dma-mapping.h b/arch/c6x/include/asm/dma-mapping.h
index 03579fd..3c69406 100644
--- a/arch/c6x/include/asm/dma-mapping.h
+++ b/arch/c6x/include/asm/dma-mapping.h
@@ -32,6 +32,7 @@ static inline int dma_set_mask(struct device *dev, u64 dma_mask)
  */
 static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
 {
+	debug_dma_mapping_error(dev, dma_addr);
 	return dma_addr == ~0;
 }
 
-- 
1.7.9.5

[PATCH RFT RESEND linux-next] c6x: dma-mapping: support debug_dma_mapping_error

[Shuah Khan]

Add support for debug_dma_mapping_error() call to avoid warning from
debug_dma_unmap() interface when it checks for mapping error checked
status. Without this patch, device driver failed to check map error
warning is generated.

Signed-off-by: Shuah Khan <shuah.khan@hp.com>
---
 arch/c6x/include/asm/dma-mapping.h |    1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/c6x/include/asm/dma-mapping.h b/arch/c6x/include/asm/dma-mapping.h
index 03579fd..3c69406 100644
--- a/arch/c6x/include/asm/dma-mapping.h
+++ b/arch/c6x/include/asm/dma-mapping.h
@@ -32,6 +32,7 @@ static inline int dma_set_mask(struct device *dev, u64 dma_mask)
  */
 static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
 {
+	debug_dma_mapping_error(dev, dma_addr);
 	return dma_addr == ~0;
 }
 
-- 
1.7.9.5

Re: [PATCH RFT RESEND linux-next] c6x: dma-mapping: support debug_dma_mapping_error

[Shuah Khan]

On Fri, 2012-10-26 at 09:40 -0600, Shuah Khan wrote:
> Add support for debug_dma_mapping_error() call to avoid warning from
> debug_dma_unmap() interface when it checks for mapping error checked
> status. Without this patch, device driver failed to check map error
> warning is generated.
> 
> Signed-off-by: Shuah Khan <shuah.khan@hp.com>
> ---
>  arch/c6x/include/asm/dma-mapping.h |    1 +
>  1 file changed, 1 insertion(+)

Would you like to this patch go through c6x arch tree or linux-next?
Please let me know your preference.

-- Shuah
> 
> diff --git a/arch/c6x/include/asm/dma-mapping.h b/arch/c6x/include/asm/dma-mapping.h
> index 03579fd..3c69406 100644
> --- a/arch/c6x/include/asm/dma-mapping.h
> +++ b/arch/c6x/include/asm/dma-mapping.h
> @@ -32,6 +32,7 @@ static inline int dma_set_mask(struct device *dev, u64 dma_mask)
>   */
>  static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
>  {
> +	debug_dma_mapping_error(dev, dma_addr);
>  	return dma_addr == ~0;
>  }
>  

Re: [PATCH RFT RESEND linux-next] c6x: dma-mapping: support debug_dma_mapping_error

[Mark Salter]

On Fri, 2012-11-02 at 10:44 -0600, Shuah Khan wrote:
> On Fri, 2012-10-26 at 09:40 -0600, Shuah Khan wrote:
> > Add support for debug_dma_mapping_error() call to avoid warning from
> > debug_dma_unmap() interface when it checks for mapping error checked
> > status. Without this patch, device driver failed to check map error
> > warning is generated.
> > 
> > Signed-off-by: Shuah Khan <shuah.khan@hp.com>
> > ---
> >  arch/c6x/include/asm/dma-mapping.h |    1 +
> >  1 file changed, 1 insertion(+)

> Would you like to this patch go through c6x arch tree or linux-next?
> Please let me know your preference.

I tried to test this but I get a build error with CONFIG_DMA_API_DEBUG:

/linux-next/lib/dma-debug.c: In function 'has_mapping_error':
/linux-next/lib/dma-debug.c:863:15: error: implicit declaration of function 'get_dma_ops' [-Werror=implicit-function-declaration]
/linux-next/lib/dma-debug.c:863:34: warning: initialization makes pointer from integer without a cast [enabled by default]

C6X (along with some other architectures) doesn't have a get_dma_ops()
function defined.

Re: [PATCH RFT RESEND linux-next] c6x: dma-mapping: support debug_dma_mapping_error

[Shuah Khan]

On Fri, 2012-11-02 at 15:10 -0400, Mark Salter wrote:
> On Fri, 2012-11-02 at 10:44 -0600, Shuah Khan wrote:
> > On Fri, 2012-10-26 at 09:40 -0600, Shuah Khan wrote:
> > > Add support for debug_dma_mapping_error() call to avoid warning from
> > > debug_dma_unmap() interface when it checks for mapping error checked
> > > status. Without this patch, device driver failed to check map error
> > > warning is generated.
> > > 
> > > Signed-off-by: Shuah Khan <shuah.khan@hp.com>
> > > ---
> > >  arch/c6x/include/asm/dma-mapping.h |    1 +
> > >  1 file changed, 1 insertion(+)
> 
> > Would you like to this patch go through c6x arch tree or linux-next?
> > Please let me know your preference.
> 
> I tried to test this but I get a build error with CONFIG_DMA_API_DEBUG:
> 
> /linux-next/lib/dma-debug.c: In function 'has_mapping_error':
> /linux-next/lib/dma-debug.c:863:15: error: implicit declaration of function 'get_dma_ops' [-Werror=implicit-function-declaration]
> /linux-next/lib/dma-debug.c:863:34: warning: initialization makes pointer from integer without a cast [enabled by default]
> 
> C6X (along with some other architectures) doesn't have a get_dma_ops()
> function defined.

That is a problem I didn't think about. I did a check and looks like c6x
and frv are the only ones that don't have get_dma_ops() defined. frv is
in a different category as it doesn't use dma_debug interfaces. IN the
case c6x, now with my change to add debug_dma_mapping_error(), we will
start seeing warnings since dma_map_page() and dma_map_single() are
debugged with a call to debug_dma_map_page() and the corresponding
dma_mapping_error() interface doesn't call debug_dma_mapping_error()
interface

- Does adding get_dma_ops() make sense? Doesn't look like c6x exports
dma_ops?

Any other ideas?

-- Shuah

Re: [PATCH RFT RESEND linux-next] c6x: dma-mapping: support debug_dma_mapping_error

[Mark Salter]

On Fri, 2012-11-02 at 13:53 -0600, Shuah Khan wrote:
> On Fri, 2012-11-02 at 15:10 -0400, Mark Salter wrote:
> > On Fri, 2012-11-02 at 10:44 -0600, Shuah Khan wrote:
> > > On Fri, 2012-10-26 at 09:40 -0600, Shuah Khan wrote:
> > > > Add support for debug_dma_mapping_error() call to avoid warning from
> > > > debug_dma_unmap() interface when it checks for mapping error checked
> > > > status. Without this patch, device driver failed to check map error
> > > > warning is generated.
> > > > 
> > > > Signed-off-by: Shuah Khan <shuah.khan@hp.com>
> > > > ---
> > > >  arch/c6x/include/asm/dma-mapping.h |    1 +
> > > >  1 file changed, 1 insertion(+)
> > 
> > > Would you like to this patch go through c6x arch tree or linux-next?
> > > Please let me know your preference.
> > 
> > I tried to test this but I get a build error with CONFIG_DMA_API_DEBUG:
> > 
> > /linux-next/lib/dma-debug.c: In function 'has_mapping_error':
> > /linux-next/lib/dma-debug.c:863:15: error: implicit declaration of function 'get_dma_ops' [-Werror=implicit-function-declaration]
> > /linux-next/lib/dma-debug.c:863:34: warning: initialization makes pointer from integer without a cast [enabled by default]
> > 
> > C6X (along with some other architectures) doesn't have a get_dma_ops()
> > function defined.
> 
> That is a problem I didn't think about. I did a check and looks like c6x
> and frv are the only ones that don't have get_dma_ops() defined. frv is

By my count, there are 14 architectures with get_dma_ops() and 14
without.

> in a different category as it doesn't use dma_debug interfaces. IN the
> case c6x, now with my change to add debug_dma_mapping_error(), we will
> start seeing warnings since dma_map_page() and dma_map_single() are
> debugged with a call to debug_dma_map_page() and the corresponding
> dma_mapping_error() interface doesn't call debug_dma_mapping_error()
> interface
> 
> - Does adding get_dma_ops() make sense? Doesn't look like c6x exports
> dma_ops?
> 
> Any other ideas?

I'm not sure. I don't know what get_dma_ops() does and it doesn't seem
to be documented anywhere.

Re: [PATCH RFT RESEND linux-next] c6x: dma-mapping: support debug_dma_mapping_error

[Shuah Khan]

On Fri, 2012-11-02 at 16:15 -0400, Mark Salter wrote:
> On Fri, 2012-11-02 at 13:53 -0600, Shuah Khan wrote:
> > On Fri, 2012-11-02 at 15:10 -0400, Mark Salter wrote:
> > > On Fri, 2012-11-02 at 10:44 -0600, Shuah Khan wrote:
> > > > On Fri, 2012-10-26 at 09:40 -0600, Shuah Khan wrote:
> > > > > Add support for debug_dma_mapping_error() call to avoid warning from
> > > > > debug_dma_unmap() interface when it checks for mapping error checked
> > > > > status. Without this patch, device driver failed to check map error
> > > > > warning is generated.
> > > > > 
> > > > > Signed-off-by: Shuah Khan <shuah.khan@hp.com>
> > > > > ---
> > > > >  arch/c6x/include/asm/dma-mapping.h |    1 +
> > > > >  1 file changed, 1 insertion(+)
> > > 
> > > > Would you like to this patch go through c6x arch tree or linux-next?
> > > > Please let me know your preference.
> > > 
> > > I tried to test this but I get a build error with CONFIG_DMA_API_DEBUG:
> > > 
> > > /linux-next/lib/dma-debug.c: In function 'has_mapping_error':
> > > /linux-next/lib/dma-debug.c:863:15: error: implicit declaration of function 'get_dma_ops' [-Werror=implicit-function-declaration]
> > > /linux-next/lib/dma-debug.c:863:34: warning: initialization makes pointer from integer without a cast [enabled by default]
> > > 
> > > C6X (along with some other architectures) doesn't have a get_dma_ops()
> > > function defined.
> > 
> > That is a problem I didn't think about. I did a check and looks like c6x
> > and frv are the only ones that don't have get_dma_ops() defined. frv is
> 
> By my count, there are 14 architectures with get_dma_ops() and 14
> without.
Right. I should have explained more. The following archs

arch/avr32/include/asm/dma-mapping.h
arch/blackfin/include/asm/dma-mapping.h
arch/cris/include/asm/dma-mapping.h
arch/mn10300/include/asm/dma-mapping.h
arch/parisc/include/asm/dma-mapping.h
arch/xtensa/include/asm/dma-mapping.h

define dma_map_page() and dma_map_single() and not call
debug_dma_map_page() interface. There is no risk of mis-matched debug
and non-debug mapping and mapping error checks like in the case of other
archs and c6x.

> > in a different category as it doesn't use dma_debug interfaces. IN the
> > case c6x, now with my change to add debug_dma_mapping_error(), we will
> > start seeing warnings since dma_map_page() and dma_map_single() are
> > debugged with a call to debug_dma_map_page() and the corresponding
> > dma_mapping_error() interface doesn't call debug_dma_mapping_error()
> > interface
> > 
> > - Does adding get_dma_ops() make sense? Doesn't look like c6x exports
> > dma_ops?
> > 
> > Any other ideas?
> 
> I'm not sure. I don't know what get_dma_ops() does and it doesn't seem
> to be documented anywhere.

It returns pointer to dma_ops like the one on alpha:

static inline struct dma_map_ops *get_dma_ops(struct device *dev)
{
        return dma_ops;
}

c6x doesn't define dma_ops looks like. Is that correct? Returning null
from get_dma_ops() is not an option as get_dma_ops() return is assumed
to be not null.

Thanks,
-- Shuah

Re: [PATCH RFT RESEND linux-next] c6x: dma-mapping: support debug_dma_mapping_error

[Mark Salter]

On Fri, 2012-11-02 at 14:26 -0600, Shuah Khan wrote:
> On Fri, 2012-11-02 at 16:15 -0400, Mark Salter wrote:
> > On Fri, 2012-11-02 at 13:53 -0600, Shuah Khan wrote:
> > > On Fri, 2012-11-02 at 15:10 -0400, Mark Salter wrote:
> > > > On Fri, 2012-11-02 at 10:44 -0600, Shuah Khan wrote:
> > > > > On Fri, 2012-10-26 at 09:40 -0600, Shuah Khan wrote:
> > > > > > Add support for debug_dma_mapping_error() call to avoid warning from
> > > > > > debug_dma_unmap() interface when it checks for mapping error checked
> > > > > > status. Without this patch, device driver failed to check map error
> > > > > > warning is generated.
> > > > > > 
> > > > > > Signed-off-by: Shuah Khan <shuah.khan@hp.com>
> > > > > > ---
> > > > > >  arch/c6x/include/asm/dma-mapping.h |    1 +
> > > > > >  1 file changed, 1 insertion(+)
> > > > 
> > > > > Would you like to this patch go through c6x arch tree or linux-next?
> > > > > Please let me know your preference.
> > > > 
> > > > I tried to test this but I get a build error with CONFIG_DMA_API_DEBUG:
> > > > 
> > > > /linux-next/lib/dma-debug.c: In function 'has_mapping_error':
> > > > /linux-next/lib/dma-debug.c:863:15: error: implicit declaration of function 'get_dma_ops' [-Werror=implicit-function-declaration]
> > > > /linux-next/lib/dma-debug.c:863:34: warning: initialization makes pointer from integer without a cast [enabled by default]
> > > > 
> > > > C6X (along with some other architectures) doesn't have a get_dma_ops()
> > > > function defined.
> > > 
> > > That is a problem I didn't think about. I did a check and looks like c6x
> > > and frv are the only ones that don't have get_dma_ops() defined. frv is
> > 
> > By my count, there are 14 architectures with get_dma_ops() and 14
> > without.
> Right. I should have explained more. The following archs
> 
> arch/avr32/include/asm/dma-mapping.h
> arch/blackfin/include/asm/dma-mapping.h
> arch/cris/include/asm/dma-mapping.h
> arch/mn10300/include/asm/dma-mapping.h
> arch/parisc/include/asm/dma-mapping.h
> arch/xtensa/include/asm/dma-mapping.h
> 
> define dma_map_page() and dma_map_single() and not call
> debug_dma_map_page() interface. There is no risk of mis-matched debug
> and non-debug mapping and mapping error checks like in the case of other
> archs and c6x.

Ah, okay. Not all architectures support HAVE_DMA_API_DEBUG. So, of those
that do, c6x seems to be the only one with dma_ops.

> 
> > > in a different category as it doesn't use dma_debug interfaces. IN the
> > > case c6x, now with my change to add debug_dma_mapping_error(), we will
> > > start seeing warnings since dma_map_page() and dma_map_single() are
> > > debugged with a call to debug_dma_map_page() and the corresponding
> > > dma_mapping_error() interface doesn't call debug_dma_mapping_error()
> > > interface
> > > 
> > > - Does adding get_dma_ops() make sense? Doesn't look like c6x exports
> > > dma_ops?
> > > 
> > > Any other ideas?
> > 
> > I'm not sure. I don't know what get_dma_ops() does and it doesn't seem
> > to be documented anywhere.
> 
> It returns pointer to dma_ops like the one on alpha:
> 
> static inline struct dma_map_ops *get_dma_ops(struct device *dev)
> {
>         return dma_ops;
> }

Okay, so what is dma_ops used for? Looks like maybe supporting different
dma features/functionality on different busses/devices.

> 
> c6x doesn't define dma_ops looks like. Is that correct? Returning null
> from get_dma_ops() is not an option as get_dma_ops() return is assumed
> to be not null.

As things stand, c6x DMA hw doesn't really need dma_ops and until this
patch, I could build in DMA debug support without dma_ops. So do we
really want to require dma_ops for dma debug support even for those
architectures which don't otherwise need it? I could add dma_ops, but
it seems silly to do so only for dma debug.

Re: [PATCH RFT RESEND linux-next] c6x: dma-mapping: support debug_dma_mapping_error

[Shuah Khan]

On Fri, 2012-11-02 at 16:59 -0400, Mark Salter wrote:
> On Fri, 2012-11-02 at 14:26 -0600, Shuah Khan wrote:
> > On Fri, 2012-11-02 at 16:15 -0400, Mark Salter wrote:
> > > On Fri, 2012-11-02 at 13:53 -0600, Shuah Khan wrote:
> > > > On Fri, 2012-11-02 at 15:10 -0400, Mark Salter wrote:
> > > > > On Fri, 2012-11-02 at 10:44 -0600, Shuah Khan wrote:
> > > > > > On Fri, 2012-10-26 at 09:40 -0600, Shuah Khan wrote:
> > > > > > > Add support for debug_dma_mapping_error() call to avoid warning from
> > > > > > > debug_dma_unmap() interface when it checks for mapping error checked
> > > > > > > status. Without this patch, device driver failed to check map error
> > > > > > > warning is generated.
> > > > > > > 
> > > > > > > Signed-off-by: Shuah Khan <shuah.khan@hp.com>
> > > > > > > ---
> > > > > > >  arch/c6x/include/asm/dma-mapping.h |    1 +
> > > > > > >  1 file changed, 1 insertion(+)
> > > > > 
> > > > > > Would you like to this patch go through c6x arch tree or linux-next?
> > > > > > Please let me know your preference.
> > > > > 
> > > > > I tried to test this but I get a build error with CONFIG_DMA_API_DEBUG:
> > > > > 
> > > > > /linux-next/lib/dma-debug.c: In function 'has_mapping_error':
> > > > > /linux-next/lib/dma-debug.c:863:15: error: implicit declaration of function 'get_dma_ops' [-Werror=implicit-function-declaration]
> > > > > /linux-next/lib/dma-debug.c:863:34: warning: initialization makes pointer from integer without a cast [enabled by default]
> > > > > 
> > > > > C6X (along with some other architectures) doesn't have a get_dma_ops()
> > > > > function defined.
> > > > 
> > > > That is a problem I didn't think about. I did a check and looks like c6x
> > > > and frv are the only ones that don't have get_dma_ops() defined. frv is
> > > 
> > > By my count, there are 14 architectures with get_dma_ops() and 14
> > > without.
> > Right. I should have explained more. The following archs
> > 
> > arch/avr32/include/asm/dma-mapping.h
> > arch/blackfin/include/asm/dma-mapping.h
> > arch/cris/include/asm/dma-mapping.h
> > arch/mn10300/include/asm/dma-mapping.h
> > arch/parisc/include/asm/dma-mapping.h
> > arch/xtensa/include/asm/dma-mapping.h
> > 
> > define dma_map_page() and dma_map_single() and not call
> > debug_dma_map_page() interface. There is no risk of mis-matched debug
> > and non-debug mapping and mapping error checks like in the case of other
> > archs and c6x.
> 
> Ah, okay. Not all architectures support HAVE_DMA_API_DEBUG. So, of those
> that do, c6x seems to be the only one with dma_ops.
> 
> > 
> > > > in a different category as it doesn't use dma_debug interfaces. IN the
> > > > case c6x, now with my change to add debug_dma_mapping_error(), we will
> > > > start seeing warnings since dma_map_page() and dma_map_single() are
> > > > debugged with a call to debug_dma_map_page() and the corresponding
> > > > dma_mapping_error() interface doesn't call debug_dma_mapping_error()
> > > > interface
> > > > 
> > > > - Does adding get_dma_ops() make sense? Doesn't look like c6x exports
> > > > dma_ops?
> > > > 
> > > > Any other ideas?
> > > 
> > > I'm not sure. I don't know what get_dma_ops() does and it doesn't seem
> > > to be documented anywhere.
> > 
> > It returns pointer to dma_ops like the one on alpha:
> > 
> > static inline struct dma_map_ops *get_dma_ops(struct device *dev)
> > {
> >         return dma_ops;
> > }
> 
> Okay, so what is dma_ops used for? Looks like maybe supporting different
> dma features/functionality on different busses/devices.
> 
> > 
> > c6x doesn't define dma_ops looks like. Is that correct? Returning null
> > from get_dma_ops() is not an option as get_dma_ops() return is assumed
> > to be not null.
> 
> As things stand, c6x DMA hw doesn't really need dma_ops and until this
> patch, I could build in DMA debug support without dma_ops. So do we
> really want to require dma_ops for dma debug support even for those
> architectures which don't otherwise need it? I could add dma_ops, but
> it seems silly to do so only for dma debug.

I agree it doesn't make sense to add dma_ops when there is no need to.
Until now dma-debug didn't depend on dma_ops. This dependency has been
introduced with the debug_dma_mapping_error() interface I added :(

Let me go back and see if I can come up with a way to not require
dma_ops for debug-dma.

Thanks,
-- Shuah

Re: [PATCH RFT RESEND linux-next] c6x: dma-mapping: support debug_dma_mapping_error

[Shuah Khan]

On Fri, 2012-11-02 at 15:08 -0600, Shuah Khan wrote:
> On Fri, 2012-11-02 at 16:59 -0400, Mark Salter wrote:
> > On Fri, 2012-11-02 at 14:26 -0600, Shuah Khan wrote:
> > > On Fri, 2012-11-02 at 16:15 -0400, Mark Salter wrote:
> > > > On Fri, 2012-11-02 at 13:53 -0600, Shuah Khan wrote:
> > > > > On Fri, 2012-11-02 at 15:10 -0400, Mark Salter wrote:
> > > > > > On Fri, 2012-11-02 at 10:44 -0600, Shuah Khan wrote:
> > > > > > > On Fri, 2012-10-26 at 09:40 -0600, Shuah Khan wrote:
> > > > > > > > Add support for debug_dma_mapping_error() call to avoid warning from
> > > > > > > > debug_dma_unmap() interface when it checks for mapping error checked
> > > > > > > > status. Without this patch, device driver failed to check map error
> > > > > > > > warning is generated.
> > > > > > > > 
> > > > > > > > Signed-off-by: Shuah Khan <shuah.khan@hp.com>
> > > > > > > > ---
> > > > > > > >  arch/c6x/include/asm/dma-mapping.h |    1 +
> > > > > > > >  1 file changed, 1 insertion(+)
> > > > > > 
> > > > > > > Would you like to this patch go through c6x arch tree or linux-next?
> > > > > > > Please let me know your preference.
> > > > > > 
> > > > > > I tried to test this but I get a build error with CONFIG_DMA_API_DEBUG:
> > > > > > 
> > > > > > /linux-next/lib/dma-debug.c: In function 'has_mapping_error':
> > > > > > /linux-next/lib/dma-debug.c:863:15: error: implicit declaration of function 'get_dma_ops' [-Werror=implicit-function-declaration]
> > > > > > /linux-next/lib/dma-debug.c:863:34: warning: initialization makes pointer from integer without a cast [enabled by default]
> > > > > > 
> > > > > > C6X (along with some other architectures) doesn't have a get_dma_ops()
> > > > > > function defined.
> > > > > 
> > > > > That is a problem I didn't think about. I did a check and looks like c6x
> > > > > and frv are the only ones that don't have get_dma_ops() defined. frv is
> > > > 
> > > > By my count, there are 14 architectures with get_dma_ops() and 14
> > > > without.
> > > Right. I should have explained more. The following archs
> > > 
> > > arch/avr32/include/asm/dma-mapping.h
> > > arch/blackfin/include/asm/dma-mapping.h
> > > arch/cris/include/asm/dma-mapping.h
> > > arch/mn10300/include/asm/dma-mapping.h
> > > arch/parisc/include/asm/dma-mapping.h
> > > arch/xtensa/include/asm/dma-mapping.h
> > > 
> > > define dma_map_page() and dma_map_single() and not call
> > > debug_dma_map_page() interface. There is no risk of mis-matched debug
> > > and non-debug mapping and mapping error checks like in the case of other
> > > archs and c6x.
> > 
> > Ah, okay. Not all architectures support HAVE_DMA_API_DEBUG. So, of those
> > that do, c6x seems to be the only one with dma_ops.
> > 
> > > 
> > > > > in a different category as it doesn't use dma_debug interfaces. IN the
> > > > > case c6x, now with my change to add debug_dma_mapping_error(), we will
> > > > > start seeing warnings since dma_map_page() and dma_map_single() are
> > > > > debugged with a call to debug_dma_map_page() and the corresponding
> > > > > dma_mapping_error() interface doesn't call debug_dma_mapping_error()
> > > > > interface
> > > > > 
> > > > > - Does adding get_dma_ops() make sense? Doesn't look like c6x exports
> > > > > dma_ops?
> > > > > 
> > > > > Any other ideas?
> > > > 
> > > > I'm not sure. I don't know what get_dma_ops() does and it doesn't seem
> > > > to be documented anywhere.
> > > 
> > > It returns pointer to dma_ops like the one on alpha:
> > > 
> > > static inline struct dma_map_ops *get_dma_ops(struct device *dev)
> > > {
> > >         return dma_ops;
> > > }
> > 
> > Okay, so what is dma_ops used for? Looks like maybe supporting different
> > dma features/functionality on different busses/devices.
> > 
> > > 
> > > c6x doesn't define dma_ops looks like. Is that correct? Returning null
> > > from get_dma_ops() is not an option as get_dma_ops() return is assumed
> > > to be not null.
> > 
> > As things stand, c6x DMA hw doesn't really need dma_ops and until this
> > patch, I could build in DMA debug support without dma_ops. So do we
> > really want to require dma_ops for dma debug support even for those
> > architectures which don't otherwise need it? I could add dma_ops, but
> > it seems silly to do so only for dma debug.
> 
> I agree it doesn't make sense to add dma_ops when there is no need to.
> Until now dma-debug didn't depend on dma_ops. This dependency has been
> introduced with the debug_dma_mapping_error() interface I added :(
> 
> Let me go back and see if I can come up with a way to not require
> dma_ops for debug-dma.

Mark/Marek,

This is for c6x to go through Marek's tree with all the other arch
patches. Hope that is ok with you Mark.

https://lkml.org/lkml/2012/11/3/219 fixes the debug_dma_mapping_error()
dependency on get_dma_ops() that caused compile errors on c6x.

Thanks,
-- Shuah

Re: [PATCH RFT RESEND linux-next] c6x: dma-mapping: support debug_dma_mapping_error

[Mark Salter]

On Thu, 2012-11-15 at 10:45 -0700, Shuah Khan wrote:
> This is for c6x to go through Marek's tree with all the other arch
> patches. Hope that is ok with you Mark.
> 
> https://lkml.org/lkml/2012/11/3/219 fixes the
> debug_dma_mapping_error()
> dependency on get_dma_ops() that caused compile errors on c6x.

Yes.

Acked-by: Mark Salter <msalter@redhat.com>