[PATCH] iommu/vt-d: constify intel_dma_ops.

[PATCH] iommu/vt-d: constify intel_dma_ops.

[Arvind Yadav]

File size before:
   text	   data	    bss	    dec	    hex	filename
  32765	    758	   1824	  35347	   8a13	drivers/iommu/intel-iommu.o

File size After adding 'const':
   text	   data	    bss	    dec	    hex	filename
  32925	    598	   1824	  35347	   8a13	drivers/iommu/intel-iommu.o

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
---
 drivers/iommu/intel-iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 90ab011..de0df48 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3970,7 +3970,7 @@ static int intel_mapping_error(struct device *dev, dma_addr_t dma_addr)
 	return !dma_addr;
 }
 
-struct dma_map_ops intel_dma_ops = {
+const struct dma_map_ops intel_dma_ops = {
 	.alloc = intel_alloc_coherent,
 	.free = intel_free_coherent,
 	.map_sg = intel_map_sg,
-- 
1.9.1

Re: [PATCH] iommu/vt-d: constify intel_dma_ops.

[Joerg Roedel]

On Tue, Jun 13, 2017 at 03:48:34PM +0530, Arvind Yadav wrote:
> File size before:
>    text	   data	    bss	    dec	    hex	filename
>   32765	    758	   1824	  35347	   8a13	drivers/iommu/intel-iommu.o
> 
> File size After adding 'const':
>    text	   data	    bss	    dec	    hex	filename
>   32925	    598	   1824	  35347	   8a13	drivers/iommu/intel-iommu.o

What is the point of those commit-messages? They just show that the
struct moved from data to the text segment. The overall size doesn't
change much.



	Joerg

Re: [PATCH] iommu/vt-d: constify intel_dma_ops.

[Arvind Yadav]

Hi,

Most dma_map_ops structures are never modified. Constify these
structures such that these can be write-protected. This file size diff
will show the difference between data and text segment.

Thanks,
~arvind

On Wednesday 28 June 2017 02:23 PM, Joerg Roedel wrote:
> On Tue, Jun 13, 2017 at 03:48:34PM +0530, Arvind Yadav wrote:
>> File size before:
>>     text	   data	    bss	    dec	    hex	filename
>>    32765	    758	   1824	  35347	   8a13	drivers/iommu/intel-iommu.o
>>
>> File size After adding 'const':
>>     text	   data	    bss	    dec	    hex	filename
>>    32925	    598	   1824	  35347	   8a13	drivers/iommu/intel-iommu.o
> What is the point of those commit-messages? They just show that the
> struct moved from data to the text segment. The overall size doesn't
> change much.
>
>
>
> 	Joerg
>

Re: [PATCH] iommu/vt-d: constify intel_dma_ops.

[Joerg Roedel]

On Wed, Jun 28, 2017 at 03:31:16PM +0530, Arvind Yadav wrote:
> Most dma_map_ops structures are never modified. Constify these
> structures such that these can be write-protected. This file size diff
> will show the difference between data and text segment.

I know what the diff shows, but it doesn't matter for this patch because
thats just an implementation detail of the compiler. The real reason for
making it 'const' is to write-protect them, and that should be clear in
the commit-message.


	Joerg