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From:   Linus Walleij <linus.walleij@linaro.org>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Russell King <rmk+kernel@arm.linux.org.uk>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc:     "Isaac J . Manjarres" <isaacmanjarres@google.com>,
        stable@vger.kernel.org, Saravana Kannan <saravanak@google.com>,
        Guenter Roeck <linux@roeck-us.net>, kernel-team@android.com,
        linux-kernel@vger.kernel.org,
        Linus Walleij <linus.walleij@linaro.org>
Subject: Re: [PATCH v3] driver core: Don't probe devices after bus_type.match() probe deferral
Date:   Tue, 30 Aug 2022 13:39:40 +0200
Message-Id: <20220830113940.331931-1-linus.walleij@linaro.org>
In-Reply-To: <20220817184026.3468620-1-isaacmanjarres@google.com>
References: <20220817184026.3468620-1-isaacmanjarres@google.com>
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> 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@vger.kernel.org
> Cc: Saravana Kannan <saravanak@google.com>
> Fixes: 656b8035b0ee ("ARM: 8524/1: driver cohandle -EPROBE_DEFER from bus_type.match()")
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Isaac J. Manjarres <isaacmanjarres@google.com>
> Tested-by: Guenter Roeck <linux@roeck-us.net>
> Reviewed-by: Saravana Kannan <saravanak@google.com>

This fixes a QEMU regression for me:
Tested-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij