linux-kernel - Re: [PATCH v2 1/7] driver core: emit uevents when device is bound to a driver

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Date:   Sat, 30 Sep 2017 10:13:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     "Ruhl, Michael J" <michael.j.ruhl@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        Tejun Heo <htejun@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH v2 1/7] driver core: emit uevents when device is bound to
 a driver

On Fri, Sep 29, 2017 at 04:23:20PM -0700, Dmitry Torokhov wrote:
> On Fri, Sep 29, 2017 at 07:40:15PM +0000, Ruhl, Michael J wrote:
> > > -----Original Message-----
> > > From: dan.j.williams@...il.com [mailto:dan.j.williams@...il.com] On
> > > Behalf Of Dan Williams
> > > Sent: Friday, September 29, 2017 3:37 PM
> > > To: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>; Tejun Heo
> > > <htejun@...il.com>; Linux Kernel Mailing List <linux-
> > > kernel@...r.kernel.org>; Guenter Roeck <linux@...ck-us.net>; Ruhl,
> > > Michael J <michael.j.ruhl@...el.com>
> > > Subject: Re: [PATCH v2 1/7] driver core: emit uevents when device is bound
> > > to a driver
> > > 
> > > On Wed, Jul 19, 2017 at 5:24 PM, Dmitry Torokhov
> > > <dmitry.torokhov@...il.com> wrote:
> > > > There are certain touch controllers that may come up in either normal
> > > > (application) or boot mode, depending on whether firmware/configuration
> > > is
> > > > corrupted when they are powered on. In boot mode the kernel does not
> > > create
> > > > input device instance (because it does not necessarily know the
> > > > characteristics of the input device in question).
> > > >
> > > > Another number of controllers does not store firmware in a non-volatile
> > > > memory, and they similarly need to have firmware loaded before input
> > > device
> > > > instance is created. There are also other types of devices with similar
> > > > behavior.
> > > >
> > > > There is a desire to be able to trigger firmware loading via udev, but it
> > > > has to happen only when driver is bound to a physical device (i2c or spi).
> > > > These udev actions can not use ADD events, as those happen too early, so
> > > we
> > > > are introducing BIND and UNBIND events that are emitted at the right
> > > > moment.
> > > >
> > > > Also, many drivers create additional driver-specific device attributes
> > > > when binding to the device, to provide userspace with additional controls.
> > > > The new events allow userspace to adjust these driver-specific attributes
> > > > without worrying that they are not there yet.
> > > >
> > > > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > > 
> > > Hi Dmitry,
> > > 
> > > Mike (cc'd) reports a regression with this change:
> > > 
> > > ---
> > > 
> > > Previously, if I did:
> > > 
> > > # rmmod hfi1
> > > 
> > > The driver would be removed.
> > > 
> > > With 4.14.0-rc2+, when I remove the driver, the PCI bus is
> > > automatically re-probed and the driver re-loaded.
> > > 
> > > ---
> > > 
> > > A bisect points to commit 1455cf8dbfd0 "driver core: emit uevents when
> > > device is bound to a driver". I'm sending this because I have this
> > > mail in my archive, but I'll let Mike follow up with any other
> > > details.
> > 
> > My test environment is RedHat 7.3 GA + 4.14.0-rc2 kernel.
> > 
> > Blacklisting the driver keeps it from being autoloaded, but this didn't seem correct.
> > 
> > With the 4.13.x branch this did not occur
> 
> Yeah, udev is being stupid. Either change ACTION=="remove" to
> ACTION!="add" in /lib/udev/rules.d/80-drivers.rules or pick this patch:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git/commit/?h=driver-core-linus&id=6878e7de6af726de47f9f3bec649c3f49e786586

I have this fix queued up for Linus, sorry for the delay in getting it
to him, hope to do that today...

thanks,

greg k-h