Using the micro-SD card

[David Corking]

On 8/23/07, David Corking <lists at dcorking.com> wrote:
> On 8/22/07, Mike Montour  wrote:
> > David Corking wrote:
> >
> > > Unfortunately, when I tried on Monday, scp exited without an error
> > > (that I recall) at 368k of a 3M file.  Today the whole 3M file
> > > transferred (and the md5 fingerprints match.)
> >
> > There's a bug filed for "I/O errors on heavy microSD writes". Is that
> > what you experienced?
> > http://bugzilla.openmoko.org/cgi-bin/bugzilla/show_bug.cgi?id=677
>
> Almost certainly yes: well spotted, Mike.  Unfortunately I was not
> paying attention at the time so I did not keep any logs.
>
> On 8/23/07, Mikko Rauhala wrote:
> > to, 2007-08-23 kello 18:44 +1200, Paul Eggleton kirjoitti:
> > > If possible, I'm thinking it would be better to use the usb gadget storage
> > > driver to provide a usb storage device on the Neo and point it at the card
> > > (after mounting). Then both the phone and the PC can access the card at the
> > > same time.
> >
> > Nuh-uh. If two systems access a filesystem (not designed spesifically
> > for that) on a block level simultaneously, you'll get horrible trouble.
> >
> > Better to serve up Neo's card over usbnet. SFTP is there already; maybe
> > a case could be made for Samba, but it would take some room...
>
> I wonder how embedded music players provide a mass storage interface.
> Maybe they use the dangerous hack that Paul suggested?

I did some googling:
http://www.linux-usb.org/gadget/file_storage.html
so I am able to guess the answer to my own question.

Music players I have tried _stop_playing_ when connected to a USB host
(similarly with digital cameras.)   Then linux-usb gadget is safe.
This may not be a very practical use case for a smartphone however.

A smartphone would need an on-screen button to unmount the microSD
card and remount it as a storage gadget.  I would be willing to give
up screen real estate for that, but I expect others would not.

-- 
David Corking, Project Manager
Corking Project Limited http://www.corking-project.co.uk/
"Total Project Management for system integration"
Tel: +44-7863-120641 Fax: +44-7863-440993