linux-kernel - Re: [PATCH] usb: phy: Restore deferred probing path

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Message-ID: <20141218082843.GC29856@ulmo>
Date:	Thu, 18 Dec 2014 09:28:44 +0100
From:	Thierry Reding <thierry.reding@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Felipe Balbi <balbi@...com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: phy: Restore deferred probing path

On Wed, Dec 17, 2014 at 09:34:48AM -0800, Greg Kroah-Hartman wrote:
> On Wed, Dec 17, 2014 at 09:30:03AM +0100, Thierry Reding wrote:
> > On Thu, Dec 04, 2014 at 01:06:07PM +0100, Thierry Reding wrote:
> > > From: Thierry Reding <treding@...dia.com>
> > > 
> > > Commit 1290a958d48e ("usb: phy: propagate __of_usb_find_phy()'s error on
> > > failure") broke platforms that rely on deferred probing to order probing
> > > of PHY and host controller drivers. The reason is that the commit simply
> > > propagates errors from __of_usb_find_phy(), which returns -ENODEV if no
> > > PHY has been registered yet for a given device tree node. The only case
> > > in which -EPROBE_DEFER would now be returned is if try_module_get() did
> > > fail, which does not make sense.
> > > 
> > > The correct thing to do is to return -EPROBE_DEFER if a PHY hasn't been
> > > registered yet. The only condition under which it makes sense to return
> > > -ENODEV is if the device tree node representing the PHY has been
> > > disabled (via the status property) because in that case the PHY will
> > > never be registered.
> > > 
> > > This patch addresses the problem by making __of_usb_find_phy() return an
> > > appropriate error code while keeping in line with the above-mentioned
> > > commit to propagate error codes rather than overwriting them. At the
> > > same time the check for a valid PHY is decoupled from the check for the
> > > try_module_get() call and a separate error code is returned if the
> > > latter fails.
> > > 
> > > Signed-off-by: Thierry Reding <treding@...dia.com>
> > > ---
> > >  drivers/usb/phy/phy.c | 14 ++++++++++----
> > >  1 file changed, 10 insertions(+), 4 deletions(-)
> > 
> > Ping?
> 
> It's the middle of the merge window, we can't do anything until 3.19-rc1
> is out at the earliest.

This fixes a regression that was introduced in commit 1290a958d48e which
has been merged for v3.19-rc1, so this really should go in as soon as
possible. I brought this up around the time of v3.18-rc5 and it's a
shame it's been broken for so long.

Thierry

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