linux-kernel - Re: [PATCH v3] driver core: Check drivers

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Message-ID: <5DE9D002-5348-4510-B975-7B558DCD6A88@nutanix.com>
Date: Tue, 4 Nov 2025 13:16:56 +0000
From: Vincent Liu <vincent.liu@...anix.com>
To: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC: "dakr@...nel.org" <dakr@...nel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org"
	<linux-pci@...r.kernel.org>
Subject: Re: [PATCH v3] driver core: Check drivers_autoprobe for all added
 devices

On 22 Oct 2025, at 13:07, Vincent Liu <vincent.liu@...anix.com> wrote:
> 
> When a device is hot-plugged, the drivers_autoprobe sysfs attribute is
> not checked (at least for PCI devices). This means that
> drivers_autoprobe is not working as intended, e.g. hot-plugged PCI
> devices will still be autoprobed and bound to drivers even with
> drivers_autoprobe disabled.
> 
> The problem likely started when device_add() was removed from
> pci_bus_add_device() in commit 4f535093cf8f ("PCI: Put pci_dev in device
> tree as early as possible") which means that the check for
> drivers_autoprobe which used to happen in bus_probe_device() is no
> longer present (previously bus_add_device() calls bus_probe_device()).
> Conveniently, in commit 91703041697c ("PCI: Allow built-in drivers to
> use async initial probing") device_attach() was replaced with
> device_initial_probe() which faciliates this change to push the check
> for drivers_autoprobe into device_initial_probe().
> 
> Make sure all devices check drivers_autoprobe by pushing the
> drivers_autoprobe check into device_initial_probe(). This will only
> affect devices on the PCI bus for now as device_initial_probe() is only
> called by pci_bus_add_device() and bus_probe_device(), but
> bus_probe_device() already checks for autoprobe, so callers of
> bus_probe_device() should not observe changes on autoprobing.
> Note also that pushing this check into device_initial_probe() rather
> than device_attach() makes it only affect automatic probing of
> drivers (e.g. when a device is hot-plugged), userspace can still choose
> to manually bind a driver by writing to drivers_probe sysfs attribute,
> even with autoprobe disabled.
> 
> Any future callers of device_initial_probe() will respect the
> drivers_autoprobe sysfs attribute, which is the intended purpose of
> drivers_autoprobe.
> 
> Signed-off-by: Vincent Liu <vincent.liu@...anix.com>
> 
> Link: https://lore.kernel.org/20251001151508.1684592-1-vincent.liu@nutanix.com
> ---
> v1->v2: Change commit subject to include driver core (no code change)
> https://lore.kernel.org/20251001151508.1684592-1-vincent.liu@nutanix.com
> v2->v3: Updated commit message to use PCI and include history (no code change)
> https://lore.kernel.org/20251013181459.517736-1-vincent.liu@nutanix.com/
> ---
> drivers/base/bus.c |  3 +--
> drivers/base/dd.c  | 10 +++++++++-
> 2 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/base/bus.c b/drivers/base/bus.c
> index 5e75e1bce551..320e155c6be7 100644
> --- a/drivers/base/bus.c
> +++ b/drivers/base/bus.c
> @@ -533,8 +533,7 @@ void bus_probe_device(struct device *dev)
> if (!sp)
> return;
> 
> - if (sp->drivers_autoprobe)
> - device_initial_probe(dev);
> + device_initial_probe(dev);
> 
> mutex_lock(&sp->mutex);
> list_for_each_entry(sif, &sp->interfaces, node)
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 13ab98e033ea..37fc57e44e54 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -1077,7 +1077,15 @@ EXPORT_SYMBOL_GPL(device_attach);
> 
> void device_initial_probe(struct device *dev)
> {
> - __device_attach(dev, true);
> + struct subsys_private *sp = bus_to_subsys(dev->bus);
> +
> + if (!sp)
> + return;
> +
> + if (sp->drivers_autoprobe)
> + __device_attach(dev, true);
> +
> + subsys_put(sp);
> }
> 
> /*
> -- 
> 2.43.7
> 

Any further comments regarding this new commit message?

Thanks,
Vincent