From mboxrd@z Thu Jan 1 00:00:00 1970 From: Or Gerlitz Subject: Re: Linux DMA address Date: Mon, 2 Jul 2012 16:53:52 +0300 Message-ID: <4FF1A7F0.10208@mellanox.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Klaus Wacker Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org On 7/2/2012 2:44 PM, Klaus Wacker wrote: > [...] So whats the nature of the returned DMA address of ib_dma_map_single and can we > assume that it is the same value on different devices on one system? Currently, over all IB drivers/devices except for ipath and qib, ib_dma_map_single is just plain dma_map_single, so your questions relates directly to the Linux DMA mapping API (and BTW - the answer is YES, in the general case you must use a DMA address you were provided when calling dma_map_single with device being X only for transactions carried over X). For those devices that hack ib_dma_map_single, it might be possible to use address provided from device X over device Y, but this is a hack, and I would strongly recommend not to have it in you code. Or. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html