linux-kernel - Re: usb: gadget: f_fs: O_NONBLOCK waits MAX_SCHEDULE

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Message-ID: <551C2AE1.9000608@mentor.com>
Date:	Wed, 1 Apr 2015 18:29:05 +0100
From:	"Baxter, Jim" <jim_baxter@...tor.com>
To:	Robert Baldyga <r.baldyga@...sung.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"Zapolskiy, Vladimir" <Vladimir_Zapolskiy@...tor.com>,
	"balbi@...com" <balbi@...com>
Subject: Re: usb: gadget: f_fs: O_NONBLOCK waits MAX_SCHEDULE_TIMEOUT

> 
> FunctionFS is very specific, because read/write operations are directly
> translated into USB requests, which are asynchronous, so you cannot use
> O_NONBLOCK.
> 
> If you need non-blocking API you can use Asynchronous I/O (AIO). You can
> find some examples in kernel sources (tools/usb/ffs-aio-example/).
> 
> Br,
> Robert Baldyga
> 

Thank you, that sounds like the best approach.
In this case I think perhaps the long wait without any data is an
problem with the imx6 Chipidea USB controller.

I guess it should suspend and drop the connections if there is no
traffic for more than 10ms?

Thanks.
Jim Baxter
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