From: nicolas.ferre@atmel.com (Nicolas Ferre)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC PATCH] scatterlist: Initialize the dma_address field with invalid dma address
Date: Fri, 10 Dec 2010 11:37:06 +0100 [thread overview]
Message-ID: <4D0202D2.8010208@atmel.com> (raw)
In-Reply-To: <20101209.120006.189701386.davem@davemloft.net>
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
WARNING: multiple messages have this Message-ID (diff)
From: Nicolas Ferre <nicolas.ferre@atmel.com>
To: David Miller <davem@davemloft.net>
Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH] scatterlist: Initialize the dma_address field with invalid dma address
Date: Fri, 10 Dec 2010 11:37:06 +0100 [thread overview]
Message-ID: <4D0202D2.8010208@atmel.com> (raw)
In-Reply-To: <20101209.120006.189701386.davem@davemloft.net>
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
next prev parent reply other threads:[~2010-12-10 10:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
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 [this message]
2010-12-10 10:37 ` Nicolas Ferre
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