From mboxrd@z Thu Jan 1 00:00:00 1970 From: wsa@the-dreams.de (Wolfram Sang) Date: Thu, 9 Aug 2018 11:23:40 +0200 Subject: [PATCH v2 2/3] i2c: Add helper to ease DMA handling In-Reply-To: <1533806000.3347.6.camel@mtksdaap41> References: <1530955795-17714-1-git-send-email-jun.gao@mediatek.com> <1530955795-17714-3-git-send-email-jun.gao@mediatek.com> <20180808205752.llowh4bvu2wkuhga@ninjato> <1533806000.3347.6.camel@mtksdaap41> Message-ID: <20180809092340.rm4ywre543hpejne@katana> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, > I believe the reason for these api is because some arch changed to can > not do DMA on stack recently. Maybe we should have dma_mapping to bounce It is not only arch dependent. You can enable virtual stacks in Kconfig, too. > buffer like it bounce un-dma-able address for those arch? or we should > have a common driver API for this, not just for i2c? I gave a talk about this problem recently and everyone in the room agreed the best thing would be to have annotated buffers which can be used kernel-wide. Someone mentioned DMABUF could be a candidate, but I haven't looked further into that. So, yes, a bigger solution is needed but I don't see that coming soon, so I implemented the I2C part for better safety now. I'd be happy to remove all that again once we have the annotated buffers. But it is an effort... Regards, Wolfram -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 833 bytes Desc: not available URL: