From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Doug Anderson <dianders@chromium.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>,
Jaehoon Chung <jh80.chung@samsung.com>,
Shawn Lin <shawn.lin@rock-chips.com>,
Adrian Hunter <adrian.hunter@intel.com>,
Stefan Agner <stefan@agner.ch>,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
Brian Norris <computersforpeace@gmail.com>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Heiko Stuebner <heiko@sntech.de>,
Jisheng Zhang <jszhang@marvell.com>,
"open list:ARM/Rockchip SoC..."
<linux-rockchip@lists.infradead.org>,
devicetree-spec@vger.kernel.org,
Mark Rutland <mark.rutland@arm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Venu Byravarasu <vbyravarasu@nvidia.com>,
Lars-Peter Clausen <lars@metafoo.de>,
Jon Hunter <jonathanh@nvidia.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
Pawel Moll <pawel.moll@arm.com>,
Ian Campbell <ijc+devicetree@hellion.org.uk>,
Grant Grundler <grundler@chromium.org>,
Kumar Gala <galak@codeaurora.org>,
"Luca Porzio (lporzio)" <lporzio@micron.com>,
Rob Herring <robh+dt@kernel.org>,
Chaotian Jing <chaotian.jing@mediatek.com>,
Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>,
Sudeep Holla <sudeep.holla@arm.com>,
zhonghui.fu@linux.intel.com, kirill.shutemov@linux.intel.com
Subject: Re: [PATCH v2 0/4] Patches to allow consistent mmc / mmcblk numbering w/ device tree
Date: Fri, 29 Apr 2016 20:57:41 +0100 [thread overview]
Message-ID: <20160429195741.GY19428@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAD=FV=VMxBYXOYOyHPeqcaWX7oU8pVrdLHOsWOWUgq-q5FshAw@mail.gmail.com>
On Fri, Apr 29, 2016 at 12:43:39PM -0700, Doug Anderson wrote:
> Russell,
>
> On Fri, Apr 29, 2016 at 11:12 AM, Russell King - ARM Linux
> <linux@arm.linux.org.uk> wrote:
> > On Fri, Apr 29, 2016 at 10:32:15AM -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:
> >
> > NAK. Really. Use UUIDs, that's the proper solution here.
>
> Un-NAK. UUIDs don't solve point #1.
Re-NAK. I don't think your point #1 is valid. See my other reply.
> * Presumably on a PC you've got an extra bit in the middle (like grub
> or something like that) that can help you resolve your UUIDs even if
> you get your kernel from somewhere else.
You are over-estimating what grub does. Grub doesn't resolve UUIDs at
all. Grub just passes the kernel arguments in its configuration file
for the entry it is booting to the kernel. It's a static configuration
found in /boot/grub/grub.conf.
It doesn't probe devices for UUIDs.
> * Presumably in the non-embedded world kernel hackers have a different
> workflow. They probably don't swap between different devices with
> different configurations on an hourly basis. They're not in the habit
> of totally reimaging their system periodically. Etc. Trying to force
> the workflow of a PC kernel hacker and an embedded kernel hacker to be
> the same doesn't seem like a worthwhile goal.
In _my_ world with the "embedded" devices I have, I mount by UUID on
platforms which have multiple MMC devices to avoid exactly the problem
you're having. This works fine.
If I were to switch the SD card, and I wanted to avoid changing the
boot loader configuration, I'd use label instead, and I'd label all
the SD card rootfs using the same label so I could just swap the cards.
> * Presumably an embedded kernel hacker running with ATA / SCSI could
> _usually_ assume that "sda" is his/her root filesystem. It's unlikely
> an embedded system would have more than one "sda" disk builtin and
> it's nearly guaranteed (I think) that a builtin ATA / SCSI controller
> would probe before any USB based devices.
You've got a funny view again. N2100 has two hard disks. The clearfog
board from SolidRun has two mini-PCIe slots, each of which can have two
SATA interfaces... If you want to use it as a server-type platform with
lots of disks...
> Sure, if your root
> filesystem is USB based (really?) and you've got additional USB
> storage devices then you're SOL. Sorry.
One of my Versatile Express platforms boots from USB, and has a MMC
slot... So this argument does not stack up.
Sorry.
--
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
next prev parent reply other threads:[~2016-04-29 19:58 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-29 17:32 [PATCH v2 0/4] Patches to allow consistent mmc / mmcblk numbering w/ device tree Douglas Anderson
2016-04-29 17:32 ` [PATCH v2 1/4] Documentation: mmc: Document mmc aliases Douglas Anderson
2016-04-29 17:32 ` [PATCH v2 2/4] mmc: read mmc alias from device tree Douglas Anderson
2016-04-29 17:32 ` [PATCH v2 3/4] mmc: use SD/MMC host ID for block device name ID Douglas Anderson
2016-04-29 17:32 ` [PATCH v2 4/4] ARM: dts: rockchip: Add mmc aliases for rk3288 platform Douglas Anderson
2016-04-29 18:12 ` [PATCH v2 0/4] Patches to allow consistent mmc / mmcblk numbering w/ device tree Rob Herring
2016-04-29 19:31 ` Doug Anderson
2016-04-29 19:50 ` Russell King - ARM Linux
2016-04-29 20:02 ` Doug Anderson
2016-04-29 18:12 ` Russell King - ARM Linux
2016-04-29 19:43 ` Doug Anderson
2016-04-29 19:57 ` Russell King - ARM Linux [this message]
2016-04-29 20:04 ` Doug Anderson
2016-04-29 21:13 ` Russell King - ARM Linux
2016-04-29 21:17 ` Doug Anderson
2016-04-29 21:29 ` Russell King - ARM Linux
2016-04-29 21:39 ` Doug Anderson
2016-04-29 21:50 ` Russell King - ARM Linux
2016-04-29 21:56 ` Doug Anderson
2016-04-29 22:16 ` Russell King - ARM Linux
2016-04-29 22:22 ` Doug Anderson
2016-04-29 22:44 ` Russell King - ARM Linux
2016-04-29 23:01 ` Doug Anderson
2016-04-29 23:58 ` Peter Hurley
[not found] ` <CAD=FV=V_YyfBOSs7BLkyhv=_5HBmf3djUWACbL6d-bwnrueDjA@mail.gmail.com>
2016-04-30 0:31 ` Peter Hurley
2016-04-30 2:29 ` Doug Anderson
2016-04-30 8:38 ` Russell King - ARM Linux
2016-04-30 13:23 ` Rob Herring
2016-04-29 22:42 ` Javier Martinez Canillas
2016-04-30 10:48 ` Russell King - ARM Linux
2016-05-03 19:17 ` Trent Piepho
2016-05-04 7:18 ` Pavel Machek
2016-05-04 12:25 ` Rob Herring
2016-05-04 12:46 ` Pavel Machek
2019-03-05 12:39 ` Måns Rullgård
2019-03-15 21:52 ` Tim Harvey
2019-03-15 23:00 ` Marek Vasut
2019-03-15 23:13 ` Tim Harvey
2019-03-15 23:23 ` Doug Anderson
[not found] ` <yw1xftrn2em9.fsf@mansr.com>
2019-03-16 12:33 ` Marek Vasut
2019-03-16 15:39 ` Russell King - ARM Linux admin
2019-03-17 15:05 ` Stefan Agner
2019-03-17 15:43 ` Russell King - ARM Linux admin
2019-03-17 15:50 ` Marek Vasut
2019-03-17 16:48 ` Måns Rullgård
2019-03-17 16:59 ` Russell King - ARM Linux admin
2019-03-27 17:37 ` Tim Harvey
2019-03-27 20:54 ` Russell King - ARM Linux admin
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