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Message-ID: <20071026024201.GA21311@kroah.com> Date: Thu, 25 Oct 2007 19:42:01 -0700 From: Greg KH <greg@...ah.com> To: Dave Young <hidave.darkstar@...il.com> Cc: Alan Stern <stern@...land.harvard.edu>, Matthew Dharm <mdharm-kernel@...-eyed-alien.net>, 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 Fri, Oct 26, 2007 at 10:01:49AM +0800, Dave Young wrote: > On 10/26/07, Greg KH <greg@...ah.com> wrote: > > On Thu, Oct 25, 2007 at 05:06:59PM +0800, Dave Young wrote: > > > On 10/19/07, Greg KH <greg@...ah.com> wrote: > > > >On Wed, Oct 17, 2007 at 10:48:52AM -0400, Alan Stern wrote: > > > >> On Tue, 16 Oct 2007, Matthew Dharm 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? > > > >> > > > >> 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. > > > >> > > > >> It's not a big deal to remove the files first. In fact, here's a > > > >> patch > > > >> to do it. Dave, see if this doesn't fix your problem. I don't like > > > >> it > > > >> much because it does an unnecessary remove/create cycle, but that's > > > >> better than doing something wrong. > > > >> > > > >> It's slightly odd that the sysfs core logs an error when you try to > > > >> create the same file twice but it doesn't when you try to remove a > > > >> non-existent file (or try to remove an existing file twice). Oh > > > >> well... > > > > > > > >I used to have the 'remove a non-existant file' warning, but that just > > > >triggered _way_ too many responses :) > > > > > > > > > > > >> Index: usb-2.6/drivers/usb/core/message.c > > > >> =================================================================== > > > >> --- usb-2.6.orig/drivers/usb/core/message.c > > > >> +++ usb-2.6/drivers/usb/core/message.c > > > >> @@ -1643,7 +1643,13 @@ free_interfaces: > > > >> intf->dev.bus_id, ret); > > > >> continue; > > > >> } > > > >> - usb_create_sysfs_intf_files (intf); > > > >> + > > > >> + /* The driver's probe method can call > > > >> usb_set_interface(), > > > >> + * which would mean the interface's sysfs files are > > > >> already > > > >> + * created. Just in case, we'll remove them first. > > > >> + */ > > > >> + usb_remove_sysfs_intf_files(intf); > > > >> + usb_create_sysfs_intf_files(intf); > > > >> } > > > > > > > >If this fixes the problem, care to resend it with a signed-off-by:? > > > > > > > >Yeah, it's not the nicest solution, but I can't think of any other one > > > >either right now :( > > > Hi, greg > > > > > > How about this patch (based on 2.6.24-rc1): > > > > > > diff -upr linux/drivers/usb/core/message.c linux.new/drivers/usb/core/message.c > > > --- linux/drivers/usb/core/message.c 2007-10-25 16:41:32.000000000 +0800 > > > +++ linux.new/drivers/usb/core/message.c 2007-10-25 16:39:38.000000000 +0800 > > > @@ -1641,7 +1641,8 @@ free_interfaces: > > > intf->dev.bus_id, ret); > > > continue; > > > } > > > - usb_create_sysfs_intf_files (intf); > > > + if(!usb_sysfs_intf_exist(intf)) > > > + usb_create_sysfs_intf_files (intf); > > > } > > > > > > usb_autosuspend_device(dev); > > > diff -upr linux/drivers/usb/core/sysfs.c linux.new/drivers/usb/core/sysfs.c > > > --- linux/drivers/usb/core/sysfs.c 2007-10-25 16:40:16.000000000 +0800 > > > +++ linux.new/drivers/usb/core/sysfs.c 2007-10-25 16:39:32.000000000 +0800 > > > @@ -728,6 +728,13 @@ static inline void usb_remove_intf_ep_fi > > > usb_remove_ep_files(&iface_desc->endpoint[i]); > > > } > > > > > > +int usb_sysfs_intf_exist(struct usb_interface *intf) > > > +{ > > > + struct device *dev = &intf->dev; > > > + > > > + return sysfs_dirent_exist(&dev->kobj, intf_attrs[0]->name); > > > > The issue is that you can't just test for the first file. If you look > > at the logic in the usb_create_sysfs_intf_file() code, we do create > > different files based on the current interface. So this might not > > always end up with the proper files in userspace, from what I can tell. > > > Yes, I know this is not good, it just fixed the bug for me. It's hard > to test all files simply. > > The duplicate file issue is still there, what to do then? > Alan, could you send the "remove before create" patch with your signed-off? I sent that patch to Linus a few hours ago :) > Anyway the sysfs_dirent_exist is useful for extern use, How about add > and export this function? Greg, If you agree, I would send it as > another patch. What would need that function? And what ensures that if you check that the file exists, it doesn't go away right after that? thanks, greg k-h - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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