From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfram Sang Subject: Re: [PATCH v2 2/3] i2c: Add helper to ease DMA handling Date: Thu, 9 Aug 2018 11:23:40 +0200 Message-ID: <20180809092340.rm4ywre543hpejne@katana> 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> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="s2qszosqjjnv6gdb" Return-path: Content-Disposition: inline In-Reply-To: <1533806000.3347.6.camel@mtksdaap41> Sender: linux-kernel-owner@vger.kernel.org To: Yingjoe Chen Cc: Jun Gao , devicetree@vger.kernel.org, srv_heupstream@mediatek.com, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: linux-i2c@vger.kernel.org --s2qszosqjjnv6gdb Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 --s2qszosqjjnv6gdb Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEOZGx6rniZ1Gk92RdFA3kzBSgKbYFAltsCBcACgkQFA3kzBSg KbZVzxAAnp4w8fWF7ktxYnYvC9JFp+Buy8W8d+Qz/WV6hTvKLPiS643wtUno8JxV lVauE1NnUkoWNxeBv/69HERf0xUBPTRhp41dcMTrWsGdcdDfYNalxTnRjwFrsenQ n4bqifiwvfuaG4VocYFc4q90lKznz0fjQxAUUkFu3w06LbPNyUXKEQW90QVcePGI Am/uhr4u6OVDOAq99KUNu0dyykS+2zYYsxNQyCskUQl/Le30MVW/UF8+zBS4NePF ClZDSm+VQfVsMEo0QvEmGWITY2PsUAIIzzXXQXL+vB5cjn6HZWPaOHbuvyTZPS5E 8w2uGICNtlkHBkBW3h7cNIkq2SMF2Q/6eh8iKfo92KsLz+0+44usgilTgt0fmubj yohov8vh13Cryzw0zlVVWS7v7ffFV0Yz0hpJY55T2TKJAmz32UKyLGb11dNMtB1+ UbKs/wznm/AjGsMeojP8oLqDurOyXwC7nF2Q3c2dsRFK4mCII87T7+zEPYKAV8dE hOGP+QhBODTg/ZRt/gCJUHYitFz6ye4rQDa1QGezTqf2t5AcpZJEqlEhb6SmG1s/ WN2RHho6lGiknRteeJ/K3Lmt/eRKzTIVN+YoGtgA6dAmndzm3B+PGwvph4kTf98p l1gmLpenGuAXB9g6IVtndNCtM4cAOTMmq+nYR+St2nIlQJgcdW0= =juxY -----END PGP SIGNATURE----- --s2qszosqjjnv6gdb--