Hi, thanks for your quick answer. Let me stress this once again... 1.) Is it possible/allowed to call ib_dma_map_single() on Linux, same buffer address, size and dma_data direction, for two different ib devices? For the data transmission we will have controls in place that not both devices write at the same time into that buffer. 2.) If this is possible, will the returned dma_addresses be the same? Any dependencies on the adapter model?
Any thoughts on this? Thanks. Kind regards Klaus Wacker IBM Systems &Technology Group, Systems Software Development SW Linux on System z Dev & Service Phone: +49-7031-16-3779 IBM Deutschland E-Mail: [email protected] Schoenaicher Str. 220 71032 Boeblingen Germany IBM Deutschland Research & Development GmbH / Vorsitzende des Aufsichtsrats: Martina Koederitz Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294 |------------> | From: | |------------> >--------------------------------------------------------------------------------------------------------------------------------------------------| |Or Gerlitz <[email protected]> | >--------------------------------------------------------------------------------------------------------------------------------------------------| |------------> | To: | |------------> >--------------------------------------------------------------------------------------------------------------------------------------------------| |Klaus Wacker/Germany/IBM@IBMDE, | >--------------------------------------------------------------------------------------------------------------------------------------------------| |------------> | Cc: | |------------> >--------------------------------------------------------------------------------------------------------------------------------------------------| |<[email protected]> | >--------------------------------------------------------------------------------------------------------------------------------------------------| |------------> | Date: | |------------> >--------------------------------------------------------------------------------------------------------------------------------------------------| |02/07/2012 15:54 | >--------------------------------------------------------------------------------------------------------------------------------------------------| |------------> | Subject: | |------------> >--------------------------------------------------------------------------------------------------------------------------------------------------| |Re: Linux DMA address | >--------------------------------------------------------------------------------------------------------------------------------------------------| 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 [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
