linux-kernel - Re: [PATCH v1] driver core: Don't probe devices after bus

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Date:   Thu, 11 Aug 2022 18:39:37 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     "Isaac J. Manjarres" <isaacmanjarres@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Russell King <rmk+kernel@....linux.org.uk>,
        Ulf Hansson <ulf.hansson@...aro.org>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] driver core: Don't probe devices after
 bus_type.match() probe deferral

On Thu, Aug 11, 2022 at 5:56 PM Guenter Roeck <linux@...ck-us.net> wrote:
>
> On 8/11/22 12:07, Isaac J. Manjarres wrote:
> > Both __device_attach_driver() and __driver_attach() check the return
> > code of the bus_type.match() function to see if the device needs to be
> > added to the deferred probe list. After adding the device to the list,
> > the logic attempts to bind the device to the driver anyway, as if the
> > device had matched with the driver, which is not correct.
> >
> > If __device_attach_driver() detects that the device in question is not
> > ready to match with a driver on the bus, then it doesn't make sense for
> > the device to attempt to bind with the current driver or continue
> > attempting to match with any of the other drivers on the bus. So, update
> > the logic in __device_attach_driver() to reflect this.
> >
> > If __driver_attach() detects that a driver tried to match with a device
> > that is not ready to match yet, then the driver should not attempt to bind
> > with the device. However, the driver can still attempt to match and bind
> > with other devices on the bus, as drivers can be bound to multiple
> > devices. So, update the logic in __driver_attach() to reflect this.
> >
> > Fixes: 656b8035b0ee ("ARM: 8524/1: driver cohandle -EPROBE_DEFER from bus_type.match()")
> > Reported-by: Guenter Roeck <linux@...ck-us.net>
> > Signed-off-by: Isaac J. Manjarres <isaacmanjarres@...gle.com>
>
> Tested-by: Guenter Roeck <linux@...ck-us.net>

Reviewed-by: Saravana Kannan <saravanak@...gle.com>

-Saravana

>
> > ---
> >   drivers/base/dd.c | 10 ++++++++++
> >   1 file changed, 10 insertions(+)
> >
> >
> > Guenter,
> >
> > Thanks for testing this patch out. Can you please add your "Tested-by"?
> >
> > --Isaac
> >
> > diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> > index 70f79fc71539..90b31fb141a5 100644
> > --- a/drivers/base/dd.c
> > +++ b/drivers/base/dd.c
> > @@ -881,6 +881,11 @@ static int __device_attach_driver(struct device_driver *drv, void *_data)
> >               dev_dbg(dev, "Device match requests probe deferral\n");
> >               dev->can_match = true;
> >               driver_deferred_probe_add(dev);
> > +             /*
> > +              * Device can't match with a driver right now, so don't attempt
> > +              * to match or bind with other drivers on the bus.
> > +              */
> > +             return ret;
> >       } else if (ret < 0) {
> >               dev_dbg(dev, "Bus failed to match device: %d\n", ret);
> >               return ret;
> > @@ -1120,6 +1125,11 @@ static int __driver_attach(struct device *dev, void *data)
> >               dev_dbg(dev, "Device match requests probe deferral\n");
> >               dev->can_match = true;
> >               driver_deferred_probe_add(dev);
> > +             /*
> > +              * Driver could not match with device, but may match with
> > +              * another device on the bus.
> > +              */
> > +             return 0;
> >       } else if (ret < 0) {
> >               dev_dbg(dev, "Bus failed to match device: %d\n", ret);
> >               return ret;
>
> --
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