[v3,15/24] media: exynos4-is: Remove call to memset after dma_alloc_coherent
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Message ID 20190715031851.6890-1-huangfq.daxian@gmail.com
State New
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Series
  • Untitled series #145755
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Commit Message

Fuqian Huang July 15, 2019, 3:18 a.m. UTC
In commit 518a2f1925c3
("dma-mapping: zero memory returned from dma_alloc_*"),
dma_alloc_coherent has already zeroed the memory.
So memset is not needed

Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
---
Changes in v3:
  - Use actual commit rather than the merge commit in the commit message

 drivers/media/platform/exynos4-is/fimc-is.c | 1 -
 1 file changed, 1 deletion(-)

Comments

Sylwester Nawrocki July 15, 2019, 9:01 a.m. UTC | #1
On 7/15/19 05:18, Fuqian Huang wrote:
> In commit 518a2f1925c3
> ("dma-mapping: zero memory returned from dma_alloc_*"),
> dma_alloc_coherent has already zeroed the memory.
> So memset is not needed

I can't see any changes in the above mentioned commit that would
make dma_alloc_coherent() (arm_coherent_dma_alloc()) zeroing its
returned memory. Maybe you need to add a reference to some other
instead?

> Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>

>  drivers/media/platform/exynos4-is/fimc-is.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/media/platform/exynos4-is/fimc-is.c b/drivers/media/platform/exynos4-is/fimc-is.c
> index e043d55133a3..77633e356305 100644
> --- a/drivers/media/platform/exynos4-is/fimc-is.c
> +++ b/drivers/media/platform/exynos4-is/fimc-is.c
> @@ -341,7 +341,6 @@ static int fimc_is_alloc_cpu_memory(struct fimc_is *is)
>  		return -ENOMEM;
>  
>  	is->memory.size = FIMC_IS_CPU_MEM_SIZE;
> -	memset(is->memory.vaddr, 0, is->memory.size);
--
Thanks, 
Sylwester
Fuqian Huang July 15, 2019, 9:43 a.m. UTC | #2
Sylwester Nawrocki <s.nawrocki@samsung.com> 於 2019年7月15日週一 下午5:00寫道:
>
> On 7/15/19 05:18, Fuqian Huang wrote:
> > In commit 518a2f1925c3
> > ("dma-mapping: zero memory returned from dma_alloc_*"),
> > dma_alloc_coherent has already zeroed the memory.
> > So memset is not needed
>
> I can't see any changes in the above mentioned commit that would
> make dma_alloc_coherent() (arm_coherent_dma_alloc()) zeroing its
> returned memory. Maybe you need to add a reference to some other
> instead?
>
In the last version patch set, I referenced the commit af7ddd8a627c
("Merge tag 'dma-mapping-4.21' of
git://git.infradead.org/users/hch/dma-mapping")
in the commit log.
The merged commit mentions that
"ensure dma_alloc_coherent returns zeroed memory to
avoid kernel data leaks through userspace.
We already did this for most common architectures,
but this ensures we do it everywhere."
dma_alloc_coherent has already zeroed the memory during allocation
and the commit also deprecates dma_zalloc_coherent.
Greg and other maintainer told me to use the actual commit
rather than the merged commit.
So I reference the commit that ensures the dma_alloc_coherent to
returns zeroed memory every where.
Maybe this belongs to the `most common achitectures` and is not impacted
by the mentioned change.
Should I rewrite the commit log? Just mention that dma_alloc_coherent
has already zeroed the memory and not to reference the commit?
Sylwester Nawrocki July 15, 2019, 11:44 a.m. UTC | #3
On 7/15/19 11:43, Fuqian Huang wrote:
> Should I rewrite the commit log? Just mention that dma_alloc_coherent
> has already zeroed the memory and not to reference the commit?

I don't think it is really needed, since at hash 518a2f1925c3 dma_alloc_coherent() 
already zeroes the memory, so in fact all statements in your current commit 
message are true.
Sylwester Nawrocki July 15, 2019, 11:45 a.m. UTC | #4
On 7/15/19 05:18, Fuqian Huang wrote:
> In commit 518a2f1925c3
> ("dma-mapping: zero memory returned from dma_alloc_*"),
> dma_alloc_coherent has already zeroed the memory.
> So memset is not needed
> 
> Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>

Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>

Patch
diff mbox series

diff --git a/drivers/media/platform/exynos4-is/fimc-is.c b/drivers/media/platform/exynos4-is/fimc-is.c
index e043d55133a3..77633e356305 100644
--- a/drivers/media/platform/exynos4-is/fimc-is.c
+++ b/drivers/media/platform/exynos4-is/fimc-is.c
@@ -341,7 +341,6 @@  static int fimc_is_alloc_cpu_memory(struct fimc_is *is)
 		return -ENOMEM;
 
 	is->memory.size = FIMC_IS_CPU_MEM_SIZE;
-	memset(is->memory.vaddr, 0, is->memory.size);
 
 	dev_info(dev, "FIMC-IS CPU memory base: %#x\n", (u32)is->memory.paddr);