Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752368Ab3IJV1c (ORCPT ); Tue, 10 Sep 2013 17:27:32 -0400 Received: from mail-bk0-f45.google.com ([209.85.214.45]:64802 "EHLO mail-bk0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751214Ab3IJV1a (ORCPT ); Tue, 10 Sep 2013 17:27:30 -0400 MIME-Version: 1.0 X-Originating-IP: [89.2.206.189] In-Reply-To: References: From: Tom Gundersen Date: Tue, 10 Sep 2013 23:27:09 +0200 Message-ID: Subject: Re: [PATCH] usb: ohci/uhci - add soft dependencies on ehci_hcd To: Alan Stern Cc: linux-usb@vger.kernel.org, LKML , "linux-modules@vger.kernel.org" , Greg Kroah-Hartman Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4465 Lines: 106 On Tue, Sep 10, 2013 at 7:31 PM, Alan Stern wrote: > On Tue, 10 Sep 2013, Tom Gundersen wrote: > >> Hi Alan, >> >> On Tue, Sep 10, 2013 at 7:02 PM, Alan Stern wrote: >> > On Tue, 10 Sep 2013, Tom Gundersen wrote: >> > >> >> Support for specifying soft dependencies in the modules themselves was >> >> introduced in commit 7cb14ba. >> >> >> >> In Arch we have always been shipping a module.d(5) fragment ordering ohci/uhci >> >> after ehci. If this ordering is really necessary, it would be great to move it >> >> to the kernel and getting the correct fragment generated by depmod. >> > >> > The ordering is more of a recommendation than a necessity. Systems >> > should work oksy if the modules are loaded in the wrong order. >> > >> > The only issue if the drivers are loaded in the wrong order is that >> > full- and low-speed devices will end up being detected and enumerated >> > twice, with a disconnection in between. This can result in >> > disconcerting messages appearing in the system log. >> > >> > In theory, it is possible for a problem to arise. For example, suppose >> > a full-speed flash drive is plugged in when the system starts up. >> > When uhci-hcd or ohci-hcd gets loaded, the drive will be detected and >> > it may even be mounted. Then when ehci-hcd loads, the drive will get >> > disconnected and reconnected. Any open file references to the original >> > mount will be orphaned. >> >> Thanks for the explanation. Sounds to me that a softdep is indeed appropriate: >> >> // >> The softdep command allows you to specify soft, or optional, module >> dependencies. modulename can be used without these optional modules >> installed, but usually with some features missing. For example, a >> driver for a storage HBA might require another module be loaded in >> order to use management features. >> >> pre-deps and post-deps modules are lists of names and/or aliases of >> other modules that modprobe will attempt to install (or remove) in >> order before and after the main module given in the modulename >> argument. >> // > > So this means that before installing ohci-hcd, modprobe would attempt > to install ehci-hcd? And if the attempt failed, it would go ahead and > load ohci-hcd anyway? Exactly. > What about during unloading? Would this mean that rmmod ohci-hcd would > automatically cause ehci-hcd to be unloaded also? Or would unloading > ehci-hcd cause ohci-hcd to be unloaded? No, unloading does not care about dependencies. >> >> Signed-off-by: Tom Gundersen >> >> Cc: Alan Stern >> >> Cc: Greg Kroah-Hartman >> >> --- >> >> drivers/usb/host/ohci-hcd.c | 1 + >> >> drivers/usb/host/uhci-hcd.c | 1 + >> >> 2 files changed, 2 insertions(+) >> >> >> >> diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c >> >> index 8f6b695..783b50a 100644 >> >> --- a/drivers/usb/host/ohci-hcd.c >> >> +++ b/drivers/usb/host/ohci-hcd.c >> >> @@ -1171,6 +1171,7 @@ EXPORT_SYMBOL_GPL(ohci_init_driver); >> >> MODULE_AUTHOR (DRIVER_AUTHOR); >> >> MODULE_DESCRIPTION(DRIVER_DESC); >> >> MODULE_LICENSE ("GPL"); >> >> +MODULE_SOFTDEP("pre: ehci_hcd"); >> >> >> >> #if defined(CONFIG_ARCH_SA1100) && defined(CONFIG_SA1111) >> >> #include "ohci-sa1111.c" >> >> diff --git a/drivers/usb/host/uhci-hcd.c b/drivers/usb/host/uhci-hcd.c >> >> index 4a86b63..c2babf3 100644 >> >> --- a/drivers/usb/host/uhci-hcd.c >> >> +++ b/drivers/usb/host/uhci-hcd.c >> >> @@ -937,3 +937,4 @@ module_exit(uhci_hcd_cleanup); >> >> MODULE_AUTHOR(DRIVER_AUTHOR); >> >> MODULE_DESCRIPTION(DRIVER_DESC); >> >> MODULE_LICENSE("GPL"); >> >> +MODULE_SOFTDEP("pre: ehci_hcd"); >> > >> > Where is MODULE_SOFTDEP defined? It isn't mentioned in any .h files in >> > my kernel tree. >> >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/linux/module.h#n104 > > I think I get the picture. > > The MODULE_SOFTDEP lines should be moved to uhci-pci.c and ohci-pci.c, > because the ordering restrictions apply only to the PCI versions of > these drivers. And they should specify "pre: ehci-pci", not ehci-hcd. Thanks, I'll send a new patch. -t -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/