Date: Fri, 29 Apr 2016 10:18:36 +0800
From: Jisheng Zhang <jszhang@marvell.com>
To: Douglas Anderson <dianders@chromium.org>, <ulf.hansson@linaro.org>,
        <jh80.chung@samsung.com>
CC: <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
Message-ID: <20160429101836.060ad087@xhacker>
In-Reply-To: <1461884805-29466-1-git-send-email-dianders@chromium.org>
References: <1461884805-29466-1-git-send-email-dianders@chromium.org>
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Dear Douglas,

On Thu, 28 Apr 2016 16:06:42 -0700 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

We also need this feature.

Thanks so much for upstreaming the series.
Jisheng

> 
>  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(-)
>