linux-kernel - Re: [linux-usb-devel] usb+sysfs: duplicate filename 'bInterfaceNumber'

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Date:	Wed, 17 Oct 2007 09:31:54 +0800
From:	"Dave Young" <hidave.darkstar@...il.com>
To:	"Alan Stern" <stern@...land.harvard.edu>,
	"Greg KH" <greg@...ah.com>,
	"Dave Young" <hidave.darkstar@...il.com>, bbpetkov@...oo.de,
	"Kernel development list" <linux-kernel@...r.kernel.org>,
	"USB development list" <linux-usb-devel@...ts.sourceforge.net>
Subject: Re: [linux-usb-devel] usb+sysfs: duplicate filename 'bInterfaceNumber'

>On 10/17/07, Matthew Dharm <mdharm-kernel@...-eyed-alien.net> wrote:
> On Tue, Oct 16, 2007 at 02:04:43PM -0400, Alan Stern wrote:
> > On Tue, 16 Oct 2007, Matthew Dharm wrote:
> >
> > > I haven't looked at this code at all, but neither approach feels right to
> > > me.
> > >
> > > How does this work at all?  Even if you load a driver later, wouldn't it
> > > call usb_set_interface(), which would call usb_create_sysfs_intf_files()
> > > and hit the same issue?
> >
> > usb_set_interface() is smart enough to remove the old interface files
> > before creating new ones, since it expects them to exist already.
> > Hence there's no problem in that scenario.
> >
> > But usb_set_configuration doesn't expect there to be any pre-existing
> > interface files, because there isn't even an interface until the
> > registration is performed.
>
> And I'm guessing that you can't call usb_create_sysfs_intf_files() until
> registration is performed, right?
>
> > The most important reason has to do with the endpoint pseudo-devices.
> > Different altsettings can have different endpoints, so those have to be
> > removed and re-created whenever the altsetting changes.
>
> Right, altsettings.  I forgot about those.  I only ever think in terms of
> multiple configurations.
>
> *grumble*
>
> If usb_set_interface() has to be smart enough to remove existing files
> first already, then I guess it's reasonably symmetric to have
> usb_set_configuration() have the same smarts.  Maybe they can share some
> common code, even.
>
> Matt
>
> --
> Matthew Dharm                              Home: mdharm-usb@...-eyed-alien.net
> Maintainer, Linux USB Mass Storage Driver
>
> C:  Why are you upgrading to NT?
> AJ: It must be the sick, sadistic streak that runs through me.
>                                         -- Chief and A.J.
> User Friendly, 5/12/1998
>

Hi,
I prefer "remove then create".

But IMHO the sysfs or driver core layer should have such  functions to
set some bit for the sysfs files creating.

Regards
dave
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