From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E64CEC34021 for ; Mon, 17 Feb 2020 16:05:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C0A4820679 for ; Mon, 17 Feb 2020 16:05:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729599AbgBQQFL (ORCPT ); Mon, 17 Feb 2020 11:05:11 -0500 Received: from mout.kundenserver.de ([212.227.126.135]:59565 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726420AbgBQQFL (ORCPT ); Mon, 17 Feb 2020 11:05:11 -0500 Received: from mail-qt1-f178.google.com ([209.85.160.178]) by mrelayeu.kundenserver.de (mreue010 [212.227.15.129]) with ESMTPSA (Nemesis) id 1Mow06-1joHJD2KlS-00qT1W; Mon, 17 Feb 2020 17:05:09 +0100 Received: by mail-qt1-f178.google.com with SMTP id d9so12334823qte.12; Mon, 17 Feb 2020 08:05:09 -0800 (PST) X-Gm-Message-State: APjAAAUoQQwJMf2dXaaZYP93Gx2Ancv6n/rct8kYpzn8ZcHu/7IvS++x tv3G4cxeX7TujOwecoAtRCGlxuo5Oh7uOMbN4XQ= X-Google-Smtp-Source: APXvYqxR24d1UtkEhBOIjI9aHRGcs1xpyahscZCl+fB1o0U8N/KlSf87IhKTr7k/p9r//9AkSP/9yAzwmpTx4NajwIA= X-Received: by 2002:ac8:3a27:: with SMTP id w36mr13631805qte.204.1581955508158; Mon, 17 Feb 2020 08:05:08 -0800 (PST) MIME-Version: 1.0 References: <20200206165755.GB3894455@kroah.com> <20200211184130.GA11908@Mani-XPS-13-9360> <20200211192055.GA1962867@kroah.com> <20200213152013.GB15010@mani> <20200213153418.GA3623121@kroah.com> <20200213154809.GA26953@mani> <20200213155302.GA3635465@kroah.com> <20200217052743.GA4809@Mani-XPS-13-9360> <20200217115930.GA218071@kroah.com> <20200217130419.GA13993@Mani-XPS-13-9360> <20200217141503.GA1110972@kroah.com> In-Reply-To: <20200217141503.GA1110972@kroah.com> From: Arnd Bergmann Date: Mon, 17 Feb 2020 17:04:52 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 02/16] bus: mhi: core: Add support for registering MHI controllers To: Greg KH Cc: Manivannan Sadhasivam , smohanad@codeaurora.org, Jeffrey Hugo , Kalle Valo , Bjorn Andersson , hemantk@codeaurora.org, linux-arm-msm , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" X-Provags-ID: V03:K1:GvetXQ1OAzDvj5SppjdPFV439MHs3fEPj9TeHxR24yoiKphxOX2 uHGdyqyI5bLLcHmRqNGAxXX6RzeVtYJiMbT8YhKNpxrtMUlRyLL5OmM6vrzFcbNURakv59l 9krdacVpdGMz/w1+Aixbvu1bRVk9ObqstejLWHqvfAgkZF6irhJLQIkzr8l1Mrv3hUYZt2P 74X5aymaVfF8LGIWUgKgQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:n1DQm7201AY=:N5S/ucW8WbB14HphQWJRNn jvfBvMZbFdh4xbiOqjuvMVRAA//XwYwTO3l4uflqGdn4Q3ZSQD8bZcO2wTHPLdac2QRnYEXut k44OvEEjS3c6aq0eWAd8tiBVWFpMNyl1OY/shQVpWMG7mmz8nomTZ/XzItexzEArhpzuwAaWA n9oXoKYbRDP3KmkCDZ1R/jK3I/lhz+UXCtWKiMKELSoLurAm+qnd7TuUjyPKbeuhTaM0Zj2O8 mi2Mv3u4GHTAIKulNBQjsHWhJ1rjgwyi7nVN5NOvQbYn15ruQVriMwGILqrOZwRPNBrkuaPaQ WpRxeEGBFGvZm44OJmJq7BTfsfIYv+pYYCe3uL14sIn3IRPW3TV6KdtM73M+Zj2dx6OfWrRWU fDmN0vKzYM41lxIHkJA6oXune3WR8HzuemmaBWTwS9uoVoTOCcPGy21nVveWJo/D8KG772Jc6 39q8I7W2z30Da0i/EnACNGgt5GBeRu6RUODxXbV8+vQ7wVx6c+wwGw124rHZIj04Th+HxkfuE r2loZgHtofv5BQWWSs+z6+XqU/aYuan/98Wd9Z/zQeAc43cDzlcTY0okjbvtSgT0gHasV/2o2 iAAWA26cYM38fKD3ew/6CYTLFhBOMrhoG6mUQdGilUE4Vgf93704/P1lXeE9SMRCm99rFB4w3 imB7KKYpaclouM+xua1PLBYUZq9yc7j5DhiwnB9KSANffZkNOOlF+nAr8g0zUA1bxKbLw//1A 5FtX4G8S0jaOKUXDKFrgqsZA0pQD//aGEs1Brl7vPSy/wUKP77dE+KqfHdHRyXPCVeeA/Gqma vG0Kbn6p3LOt3HlkusN22cpPjH7l7YqFY45fIW2k2X+a5hcZYE= Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Mon, Feb 17, 2020 at 3:15 PM Greg KH wrote: > On Mon, Feb 17, 2020 at 06:34:19PM +0530, Manivannan Sadhasivam wrote: > > On Mon, Feb 17, 2020 at 12:59:30PM +0100, Greg KH wrote: > > ``` > > struct mhi_device *mhi_alloc_device(struct mhi_controller *mhi_cntrl) > > { > > ... > > dev->parent = mhi_cntrl->dev; > > ... > > ``` > > > > Hence, having the parent dev pointer really helps. > > Yes, saving the parent device is fine, but you should be doing your own > dma calls using _your_ device, not the parents. Only mess with the > parent pointer if you need to do something "normal" for a parent. The MHI device is not involved in DMA at all, as it is not a DMA master, and has no knowledge of the memory management or whether there is any DMA at all. I think it is the right abstraction for an MHI driver to pass kernel pointers into the subsystem interfaces, which then get mapped by the bus driver that owns the DMA master. This is similar to how e.g. USB drivers pass data into the USB core interfaces, which then get the HCI driver to map/unmap it into the DMA masters. Arnd