linux-kernel - Re: [PATCHv3 2/4] usb: gadget: replace "is_dualspeed" with "max

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Message-ID: <20110823151105.GP1341@legolas.emea.dhcp.ti.com>
Date:	Tue, 23 Aug 2011 18:11:06 +0300
From:	Felipe Balbi <balbi@...com>
To:	Michal Nazarewicz <mnazarewicz@...gle.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Felipe Balbi <balbi@...com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Yang Rui Rui <ruirui.r.yang@...to.com>,
	Dave Young <hidave.darkstar@...il.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 2/4] usb: gadget: replace "is_dualspeed" with
 "max_speed"

Hi,

On Tue, Aug 23, 2011 at 05:07:11PM +0200, Michal Nazarewicz wrote:
> On Tue, 23 Aug 2011 16:58:01 +0200, Felipe Balbi <balbi@...com> wrote:
> >I stand with the fact that if they are part of the same configuration,
> >there's no way around it, storage will have to come down to full speed.
> >Unless I'm missing something.
> 
> If you look at config_buf() in composite.c, you'll notice that composite
> just skips functions that do not support current speed.  This means, that
> if a connection uses high speed but given function can handle only full
> speed, it won't be included in the descriptors.
> 
> config_buf() is called from config_desc() which similarly, iterates over
> configurations skipping the ones that do not support given speed.
> 
> Configuration is defined to support given speed if at least one function
> that is added to that configuration supports that speed (see
> usb_add_function()).

I'm trying to think if this is really what we want. This might mean
$current_config will be different depending if we connect it to SS, HS
or FS hubs. Do we need USB-IF's help here ? I guess I could drop them a
mail and ask for some clarification. Don't know how long it would take
to get an answer though :-s

-- 
balbi

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