Herve Codina 36d74f17e0 driver core: Avoid warning when removing a device while its supplier is unbinding
During driver removal, the following warning can appear:
   WARNING: CPU: 1 PID: 139 at drivers/base/core.c:1497 __device_links_no_driver+0xcc/0xfc
   ...
   Call trace:
     __device_links_no_driver+0xcc/0xfc (P)
     device_links_driver_cleanup+0xa8/0xf0
     device_release_driver_internal+0x208/0x23c
     device_links_unbind_consumers+0xe0/0x108
     device_release_driver_internal+0xec/0x23c
     device_links_unbind_consumers+0xe0/0x108
     device_release_driver_internal+0xec/0x23c
     device_links_unbind_consumers+0xe0/0x108
     device_release_driver_internal+0xec/0x23c
     driver_detach+0xa0/0x12c
     bus_remove_driver+0x6c/0xbc
     driver_unregister+0x30/0x60
     pci_unregister_driver+0x20/0x9c
     lan966x_pci_driver_exit+0x18/0xa90 [lan966x_pci]

This warning is triggered when a consumer is removed because the links
status of its supplier is not DL_DEV_DRIVER_BOUND and the link flag
DL_FLAG_SYNC_STATE_ONLY is not set.

The topology in terms of consumers/suppliers used was the following
(consumer ---> supplier):

      i2c -----------> OIC ----> PCI device
       |                ^
       |                |
       +---> pinctrl ---+

When the PCI device is removed, the OIC (interrupt controller) has to be
removed. In order to remove the OIC, pinctrl and i2c need to be removed
and to remove pinctrl, i2c need to be removed. The removal order is:
  1) i2c
  2) pinctrl
  3) OIC
  4) PCI device

In details, the removal sequence is the following (with 0000:01:00.0 the
PCI device):
  driver_detach: call device_release_driver_internal(0000:01:00.0)...
    device_links_busy(0000:01:00.0):
      links->status = DL_DEV_UNBINDING
    device_links_unbind_consumers(0000:01:00.0):
      0000:01:00.0--oic link->status = DL_STATE_SUPPLIER_UNBIND
      call device_release_driver_internal(oic)...
        device_links_busy(oic):
          links->status = DL_DEV_UNBINDING
        device_links_unbind_consumers(oic):
          oic--pinctrl link->status = DL_STATE_SUPPLIER_UNBIND
          call device_release_driver_internal(pinctrl)...
            device_links_busy(pinctrl):
              links->status = DL_DEV_UNBINDING
            device_links_unbind_consumers(pinctrl):
              pinctrl--i2c link->status = DL_STATE_SUPPLIER_UNBIND
              call device_release_driver_internal(i2c)...
                device_links_busy(i2c): links->status = DL_DEV_UNBINDING
                __device_links_no_driver(i2c)...
                  pinctrl--i2c link->status is DL_STATE_SUPPLIER_UNBIND
                  oic--i2c link->status is DL_STATE_ACTIVE
                  oic--i2c link->supplier->links.status is DL_DEV_UNBINDING

The warning is triggered by the i2c removal because the OIC (supplier)
links status is not DL_DEV_DRIVER_BOUND. Its links status is indeed set
to DL_DEV_UNBINDING.

It is perfectly legit to have the links status set to DL_DEV_UNBINDING
in that case. Indeed we had started to unbind the OIC which triggered
the consumer unbinding and didn't finish yet when the i2c is unbound.

Avoid the warning when the supplier links status is set to
DL_DEV_UNBINDING and thus support this removal sequence without any
warnings.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
Reviewed-by: Saravana Kannan <saravanak@google.com>
Link: https://patch.msgid.link/20260511155755.34428-4-herve.codina@bootlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2026-05-22 13:33:58 +02:00
2026-01-26 19:07:09 -08:00
2022-09-28 09:02:20 +02:00
2025-02-19 14:53:27 -07:00
2026-04-26 14:19:00 -07:00

Linux kernel
============

The Linux kernel is the core of any Linux operating system. It manages hardware,
system resources, and provides the fundamental services for all other software.

Quick Start
-----------

* Report a bug: See Documentation/admin-guide/reporting-issues.rst
* Get the latest kernel: https://kernel.org
* Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst
* Join the community: https://lore.kernel.org/

Essential Documentation
-----------------------

All users should be familiar with:

* Building requirements: Documentation/process/changes.rst
* Code of Conduct: Documentation/process/code-of-conduct.rst
* License: See COPYING

Documentation can be built with make htmldocs or viewed online at:
https://www.kernel.org/doc/html/latest/


Who Are You?
============

Find your role below:

* New Kernel Developer - Getting started with kernel development
* Academic Researcher - Studying kernel internals and architecture
* Security Expert - Hardening and vulnerability analysis
* Backport/Maintenance Engineer - Maintaining stable kernels
* System Administrator - Configuring and troubleshooting
* Maintainer - Leading subsystems and reviewing patches
* Hardware Vendor - Writing drivers for new hardware
* Distribution Maintainer - Packaging kernels for distros
* AI Coding Assistant - LLMs and AI-powered development tools


For Specific Users
==================

New Kernel Developer
--------------------

Welcome! Start your kernel development journey here:

* Getting Started: Documentation/process/development-process.rst
* Your First Patch: Documentation/process/submitting-patches.rst
* Coding Style: Documentation/process/coding-style.rst
* Build System: Documentation/kbuild/index.rst
* Development Tools: Documentation/dev-tools/index.rst
* Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst
* Core APIs: Documentation/core-api/index.rst

Academic Researcher
-------------------

Explore the kernel's architecture and internals:

* Researcher Guidelines: Documentation/process/researcher-guidelines.rst
* Memory Management: Documentation/mm/index.rst
* Scheduler: Documentation/scheduler/index.rst
* Networking Stack: Documentation/networking/index.rst
* Filesystems: Documentation/filesystems/index.rst
* RCU (Read-Copy Update): Documentation/RCU/index.rst
* Locking Primitives: Documentation/locking/index.rst
* Power Management: Documentation/power/index.rst

Security Expert
---------------

Security documentation and hardening guides:

* Security Documentation: Documentation/security/index.rst
* LSM Development: Documentation/security/lsm-development.rst
* Self Protection: Documentation/security/self-protection.rst
* Reporting Vulnerabilities: Documentation/process/security-bugs.rst
* CVE Procedures: Documentation/process/cve.rst
* Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst
* Security Features: Documentation/userspace-api/seccomp_filter.rst

Backport/Maintenance Engineer
-----------------------------

Maintain and stabilize kernel versions:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* Backporting Guide: Documentation/process/backporting.rst
* Applying Patches: Documentation/process/applying-patches.rst
* Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git for Maintainers: Documentation/maintainer/configure-git.rst

System Administrator
--------------------

Configure, tune, and troubleshoot Linux systems:

* Admin Guide: Documentation/admin-guide/index.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst
* Tracing/Debugging: Documentation/trace/index.rst
* Performance Security: Documentation/admin-guide/perf-security.rst
* Hardware Monitoring: Documentation/hwmon/index.rst

Maintainer
----------

Lead kernel subsystems and manage contributions:

* Maintainer Handbook: Documentation/maintainer/index.rst
* Pull Requests: Documentation/maintainer/pull-requests.rst
* Managing Patches: Documentation/maintainer/modifying-patches.rst
* Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst
* Development Process: Documentation/process/maintainer-handbooks.rst
* Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst
* Git Configuration: Documentation/maintainer/configure-git.rst

Hardware Vendor
---------------

Write drivers and support new hardware:

* Driver API Guide: Documentation/driver-api/index.rst
* Driver Model: Documentation/driver-api/driver-model/driver.rst
* Device Drivers: Documentation/driver-api/infrastructure.rst
* Bus Types: Documentation/driver-api/driver-model/bus.rst
* Device Tree Bindings: Documentation/devicetree/bindings/
* Power Management: Documentation/driver-api/pm/index.rst
* DMA API: Documentation/core-api/dma-api.rst

Distribution Maintainer
-----------------------

Package and distribute the kernel:

* Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst
* ABI Documentation: Documentation/ABI/README
* Kernel Configuration: Documentation/kbuild/kconfig.rst
* Module Signing: Documentation/admin-guide/module-signing.rst
* Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst
* Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst

AI Coding Assistant
-------------------

CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and
follow the AI coding assistants documentation before contributing to the Linux
kernel:

* Documentation/process/coding-assistants.rst

This documentation contains essential requirements about licensing, attribution,
and the Developer Certificate of Origin that all AI tools must comply with.


Communication and Support
=========================

* Mailing Lists: https://lore.kernel.org/
* IRC: #kernelnewbies on irc.oftc.net
* Bugzilla: https://bugzilla.kernel.org/
* MAINTAINERS file: Lists subsystem maintainers and mailing lists
* Email Clients: Documentation/process/email-clients.rst
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