On Fri, 16 Sep 2005, Greg KH wrote:
> > Your usb_{create|remove}_intf_ep_files routines are called whenever
> > interfaces are created or destroyed. But you also need to call them
> > whenever an altsetting is changed.
>
> Hm, where is that? ugh, I'll go dig...
It's a bit of a mess. All the relevant stuff is in message.c, and most of
the work can probably be done in usb_enable_interface and
usb_disable_interface. But in usb_disable_device and
usb_reset_configuration, _all_ the endpoints get turned off (or all but
ep0) -- so those routines don't call usb_disable_interface but simply loop
over all the endpoints.
> > Which causes difficulties, because in usb_remove_ep_files, it will no
> > longer be safe to kfree all those data structures.
>
> Why not? Those structures are only tied directly to the sysfs
> representation of the endpoint. If they go away, the memory should be
> freed.
Because a user process might be holding the attribute file open when the
altsetting is changed. The change will take effect immediately; it won't
wait for the user to close the file. So you'd be freeing memory that's
still being used by the open file.
Alan Stern
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