From mboxrd@z Thu Jan 1 00:00:00 1970 From: nicolas.ferre@atmel.com (Nicolas Ferre) Date: Fri, 10 Dec 2010 11:37:06 +0100 Subject: [RFC PATCH] scatterlist: Initialize the dma_address field with invalid dma address In-Reply-To: <20101209.120006.189701386.davem@davemloft.net> References: <1291900514-7290-1-git-send-email-nicolas.ferre@atmel.com> <20101209.120006.189701386.davem@davemloft.net> Message-ID: <4D0202D2.8010208@atmel.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Le 09/12/2010 21:00, David Miller : > From: Nicolas Ferre > 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 > > 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