Re: linux usb gadget - mass storage

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Yes, I can confirm that. The Pi Zero is running a 32-bit OS on top of
a 32-bit kernel.

János

Greg KH <greg@xxxxxxxxx> ezt írta (időpont: 2020. júl. 21., K, 16:23):
>
> On Tue, Jul 21, 2020 at 02:20:27PM +0200, SZIGETVÁRI János wrote:
> > Hi Alan,
> >
> > Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> ezt írta (időpont: 2020. júl.
> > 20., H, 19:29):
> > > 4.19 is a very old kernel.  You'd be a lot better off testing under a
> > > recent kernel, like 5.7.  It also would be more convenient to do your
> > > development on a regular PC instead of a Raspberry Pi.  You can use
> > > dummy-hcd for testing gadget drivers.
> >
> > Okay, I put together a Slackware-current based VM to conduct the
> > development work on.
> > I compiled a patched version of kernel 5.7.9 with all the necessary
> > config parameters to have USB gadget support with debugging enabled,
> > and also the dummy HCD.
> >
> > At first loaded the g_mass_storage module with a smaller ~700 MB iso
> > file, and it loaded seemingly fine, and functionality-wise it also
> > seemed to work fine, although there were frequent periodical debug
> > messages about the gadget returning command-failure status:
> > https://gist.github.com/jszigetvari/5bc4cdc8c55588907b71832558cb00a7
> >
> > After that as a test I tried to dd all the data from /dev/sr1 (that's
> > the device file the gadget was assigned) to /dev/null.
> > The process completed without any user-visible errors, although the
> > failure status related messages kept on appearing:
> > https://gist.github.com/jszigetvari/ffa19850c94f12510c0b78ed5aaba2e1
> >
> > Finally I tried to load the large, 11 GB CentOS iso file as the second
> > phase of the test. On the Raspberry Pi (with kernel 4.19) this was
> > when the crash happened, however this time it did not.
> > Originally Tiziano Bacocco's patch came around to be the time of the
> > 3.x kernels. The patch needed minimal adjustments to apply to 4.19 and
> > 5.4 and also to 5.7.9 (though there was a one line offset in
> > f_mass_storage.c).
> > https://gist.github.com/jszigetvari/5a9796c8af8a01c0edba6a8696540029
> >
> > Although I have to admit that on the Pi Zero I was using the g_multi
> > kernel module, and not g_mass_storage I assumed they share the same
> > code base, so they should work the same way.
> > On the Pi zero I need the extra serial and Ethernet interface to have
> > access to the Pi Zero, as it doesn't have a wireless NIC, and that's
> > why I chose g_multi.ko.
> >
> > In the end I did a dd with the 11 GB iso, and to my surprise it worked
> > well. dd returned without any errors and it did show the true 11 GB
> > size when it finished.
> > In the kernel logs most log entries were about block reads, but the
> > failure status messages were still around. If there was no activity on
> > the device, then they accounted for the majority of the logs
> > generated:
> > https://gist.github.com/jszigetvari/a9225fa3173e6c7b7b50673a494d9c37
> >
> > I have to admit, I stand puzzled why it worked on an x86_64-based
> > machine and crashed on the Pi Zero.
> > I guess the next step will be either:
> > * to try using g_multi instead of g_mass_storage on the test machine
> > * upgrade the Pi Zero to run kernel 5.4.x (AFAIK that's the latest one
> > can get from the Raspberry Pi Foundation's git repo), and recompile
> > that kernel version with the patch applied. (This will likely take a
> > few days.)
> >
> > Any further suggestions would also be welcome!
>
> One guess, the Pi Zero is running a 32bit kernel, while your desktop is
> running a 64bit one?
>
> greg k-h




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