linux-kernel - Re: [PATCH v3] driver core: Don't probe devices after bus

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Date:   Thu, 25 Aug 2022 15:20:23 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     "Isaac J. Manjarres" <isaacmanjarres@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Russell King <rmk+kernel@....linux.org.uk>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        stable@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        kernel-team@...roid.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] driver core: Don't probe devices after
 bus_type.match() probe deferral

On Wed, Aug 17, 2022 at 11:40 AM Isaac J. Manjarres
<isaacmanjarres@...gle.com> 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.
>
> Cc: stable@...r.kernel.org
> Cc: Saravana Kannan <saravanak@...gle.com>
> 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>
> ---
>  drivers/base/dd.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> v1 -> v2:
> - Fixed the logic in __driver_attach() to allow a driver to continue
>   attempting to match and bind with devices in case of any error, not
>   just probe deferral.
>
> v2 -> v3:
> - Restored the patch back to v1.
> - Added Guenter's Tested-by tag.
> - Added Saravana's Reviewed-by tag.
> - Cc'd stable@...r.kernel.org
>
> Greg,
>
> This is the final version of this patch. Can you please pick this up?
>
> Thanks,
> 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;
> --
> 2.37.1.595.g718a3a8f04-goog
>

Greg,

Can you pull this in for 6.0-rcX please? This is fixing a long
standing bug that was exposed by my amba code cleanup.

-Saravana