linux-kernel - Re: [PATCH] usb: gadget: don't create new string

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Message-id: <5458B8A3.4050100@samsung.com>
Date:	Tue, 04 Nov 2014 12:29:39 +0100
From:	Andrzej Pietrasiewicz <andrzej.p@...sung.com>
To:	Neil Zhang <zhangwm@...vell.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:	"balbi@...com" <balbi@...com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] usb: gadget: don't create new string_container if already
 exist

W dniu 04.11.2014 o 12:05, Neil Zhang pisze:
>
>> -----Original Message-----
>> From: Andrzej Pietrasiewicz [mailto:andrzej.p@...sung.com]
>> Sent: 2014年10月28日 21:10
>> To: Neil Zhang; linux-usb@...r.kernel.org; linux-kernel@...r.kernel.org
>> Cc: balbi@...com; gregkh@...uxfoundation.org
>> Subject: Re: [PATCH] usb: gadget: don't create new string_container if already
>> exist
>>

<snip>

>>
>> The problem you are describing does not exist in mainline kernel, where
>> functions are always unbound as part of the whole gadget's unbind - regardless
>> of whether it is a legacy gadget or configfs-composed gadget. When the whole
>> gadget is unbound, composite_dev_cleanup() is called which zeroes cdev-
>>> next_string_id and frees all gadget strings containers.
>>
>
> Yes, you are right that the current mainline won't suffer this issue.
> But it will be needed if we want to implement similar features like android do.

What features do you think of?
Mainlining the android gadget has been attempted a number of times
and is unlikely to succeed.

A configurable gadget can be composed with configfs interface,
so no need to add anything new.

That said, I think that the proper way of eliminating the problem
described is freeing the resources on function unbind rather than
preventing composite from allocating more (duplicate) resources
on bind, which your patch does.

AP
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