* [RFC PATCH] scatterlist: Initialize the dma_address field with invalid dma address
@ 2010-12-09 13:15 ` Nicolas Ferre
0 siblings, 0 replies; 6+ messages in thread
From: Nicolas Ferre @ 2010-12-09 13:15 UTC (permalink / raw)
To: linux-arm-kernel
Initialize the the dma_address field so that it will be possible to test
its value while using scatterlists. This field will be compatible with
testing by dma_mapping_error().
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
---
Hi,
I wonder why this field is not initialized in the scatterlist: is it
intentional and is there a different way to check if dma_address is a
valid field?
lib/scatterlist.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 4ceb05d..ca69409 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -85,6 +85,7 @@ EXPORT_SYMBOL(sg_last);
void sg_init_table(struct scatterlist *sgl, unsigned int nents)
{
memset(sgl, 0, sizeof(*sgl) * nents);
+ sgl->dma_address = (~(dma_addr_t)0);
#ifdef CONFIG_DEBUG_SG
{
unsigned int i;
--
1.7.3
^ permalink raw reply related [flat|nested] 6+ messages in thread* [RFC PATCH] scatterlist: Initialize the dma_address field with invalid dma address
@ 2010-12-09 13:15 ` Nicolas Ferre
0 siblings, 0 replies; 6+ messages in thread
From: Nicolas Ferre @ 2010-12-09 13:15 UTC (permalink / raw)
To: linux-kernel, linux-arm-kernel; +Cc: Nicolas Ferre
Initialize the the dma_address field so that it will be possible to test
its value while using scatterlists. This field will be compatible with
testing by dma_mapping_error().
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
---
Hi,
I wonder why this field is not initialized in the scatterlist: is it
intentional and is there a different way to check if dma_address is a
valid field?
lib/scatterlist.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 4ceb05d..ca69409 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -85,6 +85,7 @@ EXPORT_SYMBOL(sg_last);
void sg_init_table(struct scatterlist *sgl, unsigned int nents)
{
memset(sgl, 0, sizeof(*sgl) * nents);
+ sgl->dma_address = (~(dma_addr_t)0);
#ifdef CONFIG_DEBUG_SG
{
unsigned int i;
--
1.7.3
^ permalink raw reply related [flat|nested] 6+ messages in thread* [RFC PATCH] scatterlist: Initialize the dma_address field with invalid dma address
2010-12-09 13:15 ` Nicolas Ferre
@ 2010-12-09 20:00 ` David Miller
-1 siblings, 0 replies; 6+ messages in thread
From: David Miller @ 2010-12-09 20:00 UTC (permalink / raw)
To: linux-arm-kernel
From: Nicolas Ferre <nicolas.ferre@atmel.com>
Date: Thu, 9 Dec 2010 14:15:14 +0100
> Initialize the the dma_address field so that it will be possible to test
> its value while using scatterlists. This field will be compatible with
> testing by dma_mapping_error().
>
> Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Please don't do this, it's unjustified and it's going to kill performance.
Even if it were a good change, you should have used the invalid DMA
address definition defined by various architectures instead of a constant.
You should be aware of whether entries in a scatterlist have been setup
by your code path.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH] scatterlist: Initialize the dma_address field with invalid dma address
@ 2010-12-09 20:00 ` David Miller
0 siblings, 0 replies; 6+ messages in thread
From: David Miller @ 2010-12-09 20:00 UTC (permalink / raw)
To: nicolas.ferre; +Cc: linux-kernel, linux-arm-kernel
From: Nicolas Ferre <nicolas.ferre@atmel.com>
Date: Thu, 9 Dec 2010 14:15:14 +0100
> Initialize the the dma_address field so that it will be possible to test
> its value while using scatterlists. This field will be compatible with
> testing by dma_mapping_error().
>
> Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Please don't do this, it's unjustified and it's going to kill performance.
Even if it were a good change, you should have used the invalid DMA
address definition defined by various architectures instead of a constant.
You should be aware of whether entries in a scatterlist have been setup
by your code path.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [RFC PATCH] scatterlist: Initialize the dma_address field with invalid dma address
2010-12-09 20:00 ` David Miller
@ 2010-12-10 10:37 ` Nicolas Ferre
-1 siblings, 0 replies; 6+ messages in thread
From: Nicolas Ferre @ 2010-12-10 10:37 UTC (permalink / raw)
To: linux-arm-kernel
Le 09/12/2010 21:00, David Miller :
> From: Nicolas Ferre <nicolas.ferre@atmel.com>
> Date: Thu, 9 Dec 2010 14:15:14 +0100
>
>> Initialize the the dma_address field so that it will be possible to test
>> its value while using scatterlists. This field will be compatible with
>> testing by dma_mapping_error().
>>
>> Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
>
> Please don't do this, it's unjustified and it's going to kill performance.
Yes, that is what I suspected...
> Even if it were a good change, you should have used the invalid DMA
> address definition defined by various architectures instead of a constant.
Well this definition seems to be spread among drivers (mostly usb ones):
DMA_ADDR_INVALID...
And also sometimes with different names:
DMA_INVALID_HANDLE, INVALID_DMA_ADDRESS
> You should be aware of whether entries in a scatterlist have been setup
> by your code path.
Yes, in fact my need is related to the fact that my scatterlist is
filled in a driver and then handled by the dmaengine driver.
But I will reconsider the path taken by my sg to be able to avoid
checking the dma_address field.
Best regards,
--
Nicolas Ferre
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH] scatterlist: Initialize the dma_address field with invalid dma address
@ 2010-12-10 10:37 ` Nicolas Ferre
0 siblings, 0 replies; 6+ messages in thread
From: Nicolas Ferre @ 2010-12-10 10:37 UTC (permalink / raw)
To: David Miller; +Cc: linux-kernel, linux-arm-kernel
Le 09/12/2010 21:00, David Miller :
> From: Nicolas Ferre <nicolas.ferre@atmel.com>
> Date: Thu, 9 Dec 2010 14:15:14 +0100
>
>> Initialize the the dma_address field so that it will be possible to test
>> its value while using scatterlists. This field will be compatible with
>> testing by dma_mapping_error().
>>
>> Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
>
> Please don't do this, it's unjustified and it's going to kill performance.
Yes, that is what I suspected...
> Even if it were a good change, you should have used the invalid DMA
> address definition defined by various architectures instead of a constant.
Well this definition seems to be spread among drivers (mostly usb ones):
DMA_ADDR_INVALID...
And also sometimes with different names:
DMA_INVALID_HANDLE, INVALID_DMA_ADDRESS
> You should be aware of whether entries in a scatterlist have been setup
> by your code path.
Yes, in fact my need is related to the fact that my scatterlist is
filled in a driver and then handled by the dmaengine driver.
But I will reconsider the path taken by my sg to be able to avoid
checking the dma_address field.
Best regards,
--
Nicolas Ferre
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2010-12-10 10:37 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2010-12-09 13:15 [RFC PATCH] scatterlist: Initialize the dma_address field with invalid dma address Nicolas Ferre
2010-12-09 13:15 ` Nicolas Ferre
2010-12-09 20:00 ` David Miller
2010-12-09 20:00 ` David Miller
2010-12-10 10:37 ` Nicolas Ferre
2010-12-10 10:37 ` Nicolas Ferre
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.