On 4/17/2018 12:12 PM, Dave Jiang wrote: > > On 04/13/2018 07:12 PM, Sujeev Dias wrote: >> Hi >> >> Can we please revert this patch because it breaks qcom dma-engine drivers and many consumers after >> we propagated to 4.14 kernel. >> >> commit: c678fa66341c7b82a57cfed0ba3656162e970f99 >> dmaengine: remove DMA_SG as it is dead code in kernel >> >> I don't see any alternate methods we can use either. We cannot use standard dma_memcpy >> api's since argument for both src and destination dma_addr. Because dma mapping has to >> be done by dma controller (due to smmu/sid configurations), client must pass host DDR >> address as a cpu address not dma_addr. >> >> Thanks >> Sujeev >> > Sujeev, > At least IMO, when you don't have in kernel upstream consumer for the > code, it's dead code for the kernel. In the end, it's Vinod's call. > However, I do think in the future we will need support for DMA engines > that want to take virtual memory addresses instead of DMA addresses with > SMMU/SID type of implementation. So something new needs to be introduced.... If I remember this right, another implementation was going to replace DMA_SG. DMA_SG got reverted but the new implementation wasn't put in place for some reason. Given we have few users of DMA Engine, I believe we should try to keep as much functionality as possible in the kernel to allow new features to be developed rather than limiting people's choices. -- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project. -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
