From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753738AbcEDTZP (ORCPT ); Wed, 4 May 2016 15:25:15 -0400 Received: from mout.kundenserver.de ([212.227.126.134]:62425 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752492AbcEDTZM (ORCPT ); Wed, 4 May 2016 15:25:12 -0400 From: Arnd Bergmann To: Douglas Anderson Cc: ulf.hansson@linaro.org, jh80.chung@samsung.com, shawn.lin@rock-chips.com, adrian.hunter@intel.com, stefan@agner.ch, linux-mmc@vger.kernel.org, computersforpeace@gmail.com, dmitry.torokhov@gmail.com, mark.rutland@arm.com, vbyravarasu@nvidia.com, justin.wang@spreadtrum.com, ksumrall@android.com, lars@metafoo.de, dtor@chromium.org, jonathanh@nvidia.com, huangtao@rock-chips.com, devicetree@vger.kernel.org, pawel.moll@arm.com, ijc+devicetree@hellion.org.uk, galak@codeaurora.org, lporzio@micron.com, robh+dt@kernel.org, chuanxiao.dong@intel.com, chaotian.jing@mediatek.com, sergei.shtylyov@cogentembedded.com, linux-kernel@vger.kernel.org, sudeep.holla@arm.com Subject: Re: [PATCH 0/3] Patches to allow consistent mmc / mmcblk numbering Date: Fri, 29 Apr 2016 19:39:09 +0200 Message-ID: <1659435.FBgTBXnguZ@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1461884805-29466-1-git-send-email-dianders@chromium.org> References: <1461884805-29466-1-git-send-email-dianders@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:ydP2UM56k5ZNeuEo2LPeWb2o/2bC3JUqaEkeTNaGod4GbYQpRy6 mV+AneO70ndy5WmaAfzNKz2sRvbWuRSU2OkuEq8xQXvG0mOez+5fH2jzkwd1kxXLuKEC+Jj pZB/+rfw9/yLg7HP3C877shrKcSuTW/03bgxHvyapvT0MXQ9MfosYj81AqdPA819QWSWTgu /r+4dvOY/tagCTnvTiDPg== X-UI-Out-Filterresults: notjunk:1;V01:K0:XR9eGdg6WAo=:cC1+n9V0q8B4R1UrJGewKz ZcU+Jr7l3Q+7pG0bSLsNOgEXU0lSxQOnbrfQ3J7D/EShA8i90AgzE20sK7gDiFt18Ye1PePje RwWWp3FYfGCGXDFBDHDKriNa9+60SUwkALnPA4tPsri1k4RZMJvLaN7bV9jhoh7RNep/F3Pot lFDfh7fd0kx4V5nIoWUhGLeK894CcBRLVSzBX+VzuUdHnL2rfgTKS+uvDL5i9NA78Bxg8Nx4r F0n6+zu8HEIfkNsE8xJ11/OoJf2XNhiJxFm9Dx4JIH5aRWso6EvcgtMqveHES1d3fARw1Pmt4 v3ATX3Stb+X5Nx0R+sXk3wV8my4FhYDMIyYyq84IFYWza0Dnq3NGE/xBZki/g1EYLk3JFR9sf h/FzMGqQPu+ZrVDcl+EjOI/U3Rt+yZzwnCFSpGNVxAANGiLivLUWgJrBpwz26IMjw9hDL21hW mYXwsWUYv6GSv806ZnDBcSb2YSfqBzQY8JHQDPf/i+zAKPHrQ2DbFRXmPOAlpc6+BAW+o9G64 KqD+tTxYBx5nJF6dYjHs8E0zPQyu97pa+d0kOBdyNKbPSzZMcdW+doh5bAoXJRIMbFjWydWVf wdqkHjr9YcWZlT09/Ng4skIe6uoJqn/CFJxfAvLnetKop9vBoknhAjS8fgQK/HFwSFN7TvPG3 TEllfWJItB4+6zJ3DC5Etf4kEm4WBU9m07GbOQ1tO1NHm5+oQrQSZ7WodOo9hlNFLON+uO8hZ 4q13MlnviIusqn0v Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 28 April 2016 16:06:42 Douglas Anderson wrote: > This series picks patches from various different places to produce what > I consider the best solution to getting consistent mmc and mmcblk > ordering. > > Why consistent ordering and why not just use UUIDs? IMHO consistent > ordering solves a few different problems: > > 1. For poor, feeble-minded humans like me, have sane numbering for > devices helps a lot. When grepping through dmesg it's terribly handy > if a given SDMMC device has a consistent number. I know that I can > do "dmesg | grep mmc0" or "dmesg | grep mmcblk0" to find info about > the eMMC. I know that I can do "dmesg | grep mmc1" to find info > about the SD card slot. I don't want it to matter which one probed > first, I don't want it to matter if I'm working on a variant of the > hardware that has the SD card slot disabled, and I don't want to care > what my boot device was. Worrying about what device number I got > increases my cognitive load. > > 2. There are cases where it's not trivially easy during development to > use the UUID. Specifically I work a lot with coreboot / depthcharge > as a BIOS. When configured properly, that BIOS has a nice feature to > allow you to fetch the kernel and kernel command line from TFTP by > pressing Ctrl-N. In this particular case the BIOS doesn't actually > know which disk I'd like for my root filesystem, so it's not so easy > for it to put the right UUID into the command line. For this > purpose, knowing that "mmcblk0" will always refer to eMMC is handy. > > > Jaehoon Chung (1): > Documentation: mmc: Document mmc aliases > > Stefan Agner (2): > mmc: read mmc alias from device tree > mmc: use SD/MMC host ID for block device name ID > > Documentation/devicetree/bindings/mmc/mmc.txt | 11 +++++++++++ > drivers/mmc/card/block.c | 3 ++- > drivers/mmc/core/host.c | 25 ++++++++++++++++++++----- > 3 files changed, 33 insertions(+), 6 deletions(-) Does this mean we can revert 9aaf343 ("mmc: block: Use the mmc host device index as the mmcblk device index") for now and wait until this is in as well? The commit I mention here breaks a significant number of boots on Olof's test build setup, and it would be nice to avoid breaking them again when we get yet another device numbering system. Arnd