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

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Date:	Wed, 24 Aug 2011 16:53:52 +0200
From:	"Michal Nazarewicz" <mnazarewicz@...gle.com>
To:	"Alan Stern" <stern@...land.harvard.edu>
Cc:	"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"

> On Wed, 24 Aug 2011, Michal Nazarewicz wrote:
>> I'm actually wondering whether we really need to worry about it.
>> composite_driver has the “max_speed” field and I would just leave it as
>> composite driver's author responsibility to put correct value there.
>>
>> One thing that could be worth doing is iterate over all the  
>> configurations and figure out if at least one supports the speed
>> declared by “max_speed” and if not, lower it.

On Wed, 24 Aug 2011 16:31:27 +0200, Alan Stern <stern@...land.harvard.edu>  
wrote:
> That's the same as what I said: Use the highest speed supported by any
> function driver.

Right.

>> Like I've said before, as additional functionality, composite.c could
>> check if it's USB_SPEED_UNKWONW in which case it would look for the  
>> lowest speed that all the functions support.

> It's reasonable.  Just be sure to document it properly; otherwise
> nobody will understand or remember it!

I've found where my reasoning was faulty.  The usb_gadget_driver's
max_speed is set before all the functions get added so composite.c has
no way to figure those things in advance.  That's why we need to relay
on usb_composite_driver's max_speed be set to a proper value.

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michal "mina86" Nazarewicz    (o o)
ooo +-----<email/xmpp: mnazarewicz@...gle.com>-----ooO--(_)--Ooo--
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