Re: /dev/disk0 vs /dev/mmc0

[David Jander <david.jander@protonic.nl>]

Hi Jean-Christophe,

On Thu, 3 Oct 2013 21:23:49 +0200
Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com> wrote:

> On 17:17 Thu 03 Oct     , David Jander wrote:
> > 
> > Hi all,
> > 
> > I am following barebox git closely and noticed a change recently: Device
> > names for MMC (MCI) and USB mass-storage devices have changed to the
> > generic "/dev/diskX". Earlier an MMC device was named "/dev/mmc0".
> > Unfortunately this change breaks my /env/bin/init script and I don't know
> > how to fix it. I relied on the existence of certain devices to distinguish
> > between USB mass-storage device presence and/or SD-card presence. How can
> > I do this with this new device naming convention?
> > 
> > I used to have these kind of checks in /env/bin/init:
> > 
> > # Mount MMC (first partition) if available
> > if [ -e "/dev/mmc0.0" ]; then
> >         mkdir /mmc
> >         mount /dev/mmc0.0 /mmc
> >         if [ -e "/mmc/uImage" ]; then
> >                 boot_target="mmc"
> >         fi
> > fi
> > 
> > Booting like this is only allowed from MMC and not from USB, and now it
> > seems impossible to distinguish between them anymore.
> > 
> > Btw, why was this changed in the first place?
> 
> now you an use devname parameter to specify a specifc name for mmc

My board is fully device-tree based, but your suggestion pointed me in the
right direction: the "alias" section seems to have a whole new meaning now ;-)
I hope this won't interfere with Linux, since I intend to use a single DT for
both Barebox _and_ Linux.

> not all the drivers have the platform_data update to support but it will be
> easy enough to add it
> 
> I recently add this to atmel_mci and animeo_ip board

Didn't find that one... probably not in mainline yet? Never mind.

> and I recomment you to switch to defaultenv-2 for this
> 
> and use boot sequence this will simplify your env hugely

Although I agree defaultenv-2 looks pretty cool and will add a lot of
convenience and flexibility for complex systems, IMHO it will not simplify the
env of this board the least bit :-)
In fact, on a simple embedded system that has to have a strictly predefined
boot-behavior with a few simple rules, it is overly complex and if an
"outsider" ever needs to understand how it works, that can be a bit of a
problem (the default boot path probably going through some 5 different
scripts with lots of compound config-variables).

Best regards,

-- 
David Jander
Protonic Holland.

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