linux-kernel - Re: [PATCH] USB: OHCI/UHCI: Add soft dependencies on ehci

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Message-ID: <af0e1bc5-d08d-4b66-9a0b-4c39f17a043b@rowland.harvard.edu>
Date: Tue, 30 Dec 2025 11:23:40 -0500
From: Alan Stern <stern@...land.harvard.edu>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Huacai Chen <chenhuacai@...ngson.cn>,
	Huacai Chen <chenhuacai@...nel.org>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Shengwen Xiao <atzlinux@...a.com>
Subject: Re: [PATCH] USB: OHCI/UHCI: Add soft dependencies on ehci_hcd

On Tue, Dec 30, 2025 at 09:15:36AM +0100, Greg Kroah-Hartman wrote:
> On Tue, Dec 30, 2025 at 04:00:14PM +0800, Huacai Chen wrote:
> > Commit 9beeee6584b9aa4f ("USB: EHCI: log a warning if ehci-hcd is not
> > loaded first") said that ehci-hcd should be loaded before ohci-hcd and
> > uhci-hcd. However, commit 05c92da0c52494ca ("usb: ohci/uhci - add soft
> > dependencies on ehci_pci") only makes ohci-pci/uhci-pci depend on ehci-
> > pci, which is not enough and we may still see the warnings in boot log.
> > So fix it by also making ohci-hcd/uhci-hcd depend on ehci-hcd.
> > 
> > Cc: stable@...r.kernel.org
> > Reported-by: Shengwen Xiao <atzlinux@...a.com>
> > Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> > ---
> >  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 9c7f3008646e..549c965b7fbe 100644
> > --- a/drivers/usb/host/ohci-hcd.c
> > +++ b/drivers/usb/host/ohci-hcd.c
> > @@ -1355,4 +1355,5 @@ static void __exit ohci_hcd_mod_exit(void)
> >  	clear_bit(USB_OHCI_LOADED, &usb_hcds_loaded);
> >  }
> >  module_exit(ohci_hcd_mod_exit);
> > +MODULE_SOFTDEP("pre: ehci_hcd");
> 
> Ick, no, this way lies madness.  I hate the "softdep" stuff, it's
> usually a sign that something is wrong elsewhere.
> 
> And don't add this _just_ to fix a warning message in a boot log, if you
> don't like that message, then build the module into your kernel, right?
> 
> And I really should just go revert 05c92da0c524 ("usb: ohci/uhci - add
> soft dependencies on ehci_pci") as well, that feels wrong too.

This might also be a good time to revert 9beeee6584b9 ("USB: EHCI: log a 
warning if ehci-hcd is not loaded first").  Firstly, because it doesn't 
test the right condition; what matters is not whether ehci-hcd is loaded 
before uhci-hcd and ohci-hcd, but whether ehci-pci is loaded before 
uhci-pci and ohci-pci.

And secondly, because if the warning hasn't convinced people to fix the 
order of module loading after seventeen years, it's not likely to do so 
in the future.

Alan Stern