usb mass media storage

[Christian Adams]

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moinmoin

there is no "must" for using /dev/mmc* .. you could also use a plain  
file:

preparations:

create mem_stick.fs file
dd if=/dev/zero of=mem_stick.fs bs=512 count=1048576 # for a 512mb  
"memory-stick" with blocksize=512 bytes

create filesystem on mem_stick.fs:
mkfs.ext3 mem_stick.fs

from FR you can mount this filesystem with:
mount -o loop mem_stick.fs some_mount_point

and for exporting via usb:

rmmod g_ether
# if mount -> umount!
modprobe g_file_storage file=mem_stick.fs

regards, morlac


Am 05.09.2008 um 13:04 schrieb pHilipp Zabel:

> On Fri, Sep 5, 2008 at 4:41 AM, Dale Maggee  
> <antisol at internode.on.net> wrote:
>> Petr Vanek wrote:
>>> I have spent a while googling this up and have no wiki skills but
>>> someone might find this useful:
>>>
>>> to make FR act as a memory stick, here is what my script does:
>>>
>>>
>>> #!/bin/sh
>>> /etc/init.d/networking stop
>>> rmmod g_ether
>>> modprobe g_file_storage file=/dev/mmcblk0p1
>>>
>>> --
>>> Petr Vaněk
>>> http://biodynamika.cz
>>>
>> very cool, but before I test it out (potentially breaking my usb
>> networking in the process), I have a couple of questions:
>>
>> 1. will this persist over a reboot, or will it revert back to  
>> being an
>> ethernet gadget when I reboot?
>
> It's not persistent unless you add something like this to the init
> scripts. After rebooting the ethernet gadget will be back.
>
>> 2. is the following sufficient to switch it back?
>>
>> #!/bin/sh
>> rmmod g_file_storage
>> modprobe g_ether
>> ifup usb0
>>
>> (assuming I replaced '/etc/init.d/networking stop' with 'ifdown  
>> usb0' as
>> recommended by Daniel)
>>
>> 3. can somebody point me to a resource for the g_file_storage module
>> where I can learn more about it? I did a couple of quick googles but
>> didn't see anything promising. specifically I'd like to know more  
>> about
>> the file parameter - I assume that in this scenario our "usb  
>> stick" is
>> using partition/device information from /dev/mmcblk0p1, and will be
>> partitioned in the same way as the SD card? what If I wanted to  
>> have my
>> home directory accessible in "usb stick" mode?
>
> I suggest to read the comment in the source code, it's quite detailed:
> http://git.kernel.org/?p=linux/kernel/git/torvalds/ 
> linux-2.6.git;a=blob;f=drivers/usb/gadget/file_storage.c;hb=HEAD
>
> The file parameter determines the raw backing store for the storage
> device, so if you
> have file=/dev/mmcblk0p1, its contents will directly appear as
> /dev/sdx on the host. As mmcblk0p1 doesn't contain a partition table,
> so won't sdx. If you want to export the whole device, use
> file=/dev/mmcblk0, you'll get the partition table in /dev/sdx and the
> kernel will parse it and create /dev/sdx1 (containing the contents of
> /dev/mmcblk0p1) etc.
>
> The host has direct access to the block device, so it is important
> that /dev/mmcblk0p1 is not mounted on both the phone and the host at
> the same time (unless it's mounted ro on both).
>
> regards
> Philipp
> _______________________________________________
> Openmoko community mailing list
> community at lists.openmoko.org
> http://lists.openmoko.org/mailman/listinfo/community
>

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