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Message-ID: <1b385c4a779b0d6722e74894aec0ba0a3855c72f.camel@kernel.crashing.org>
Subject: Re: f_mass_storage vs drivers/target
From:   Benjamin Herrenschmidt <benh@kernel.crashing.org>
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     USB list <linux-usb@vger.kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date:   Thu, 22 Aug 2019 15:48:42 +1000
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On Thu, 2019-08-22 at 15:14 +1000, Benjamin Herrenschmidt wrote:
> - No UDC driver other than dummy sets max_streams, and f_tcm requires 4,
> so f_tcm will fail with *any* superspeed UDC driver as far as I can tell.
> 
> Was it ever tested with USB 3 ?

Ok so I spoke too soon... dwc3 does, I didn't notice bcs it doesn't
live in drivers/usb/gadget...

So Sebastian, what would be the best way to "fallback" to non-stream
use rather than just fail probing ?

Do we really want the autoconf EP matching to enforce the stream
numbers ? If we allow it to not match, then f_tcm could check after
matching if enough streams were found and disable stream support if
not.

Another option would be to make this 2-pass, though that complicates
even more: a first pass where we enforce the stream count, and if
we fail, a second pass where we ignore them.

Suggestions ?

Cheers,
Ben.