From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Lukas Wunner <lukas@wunner.de>
Cc: Linux PM list <linux-pm@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Alan Stern <stern@rowland.harvard.edu>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Tomeu Vizoso <tomeu.vizoso@collabora.com>,
Mark Brown <broonie@kernel.org>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Kevin Hilman <khilman@kernel.org>,
Ulf Hansson <ulf.hansson@linaro.org>,
"Luis R. Rodriguez" <mcgrof@suse.com>,
Jonathan Corbet <corbet@lwn.net>
Subject: Re: [RFC/RFT][PATCH v3 0/5] Functional dependencies between devices
Date: Wed, 28 Sep 2016 02:33:21 +0200 [thread overview]
Message-ID: <1618935.9CTdqGRBy5@vostro.rjw.lan> (raw)
In-Reply-To: <20160927123429.GA5828@wunner.de>
On Tuesday, September 27, 2016 02:34:29 PM Lukas Wunner wrote:
> [+cc corbet]
>
> To whom it may concern,
>
> I made some notes while reviewing the state machine in patch 2 of this
> series and thought, why not rework it into something that could eventually
> go into the Documentation/ tree?
>
> So here's an initial draft. There's some introductory text plus
> a description of the state machine. Just putting this out there now
> to ease reviewers' lives, despite the obvious WIP status. I'll try to
> amend it as the series converges.
>
> This is already rst-formatted but I haven't actually run it through
> sphinx yet.
Thanks a lot for doing this!
It looks good to me in general. I think it would be good to add it to the
series at one point (if you don't mind).
I'm only a bit reluctant about advertising the usage of links between children
and parents, because that doesn't look like the right tool for the purpose
(as I said before, I'd prefer to add a device flag causing the parent driver
to be probed before the child one if needed).
Thanks,
Rafael
> -- >8 --
>
> Subject: [PATCH] Documentation: device links: Add initial documentation
>
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> ---
> Documentation/driver-model/device_link.rst | 95 ++++++++++++++++++++++++++++++
> 1 file changed, 95 insertions(+)
> create mode 100644 Documentation/driver-model/device_link.rst
>
> diff --git a/Documentation/driver-model/device_link.rst b/Documentation/driver-model/device_link.rst
> new file mode 100644
> index 0000000..ba911b4
> --- /dev/null
> +++ b/Documentation/driver-model/device_link.rst
> @@ -0,0 +1,95 @@
> +============
> +Device links
> +============
> +
> +By default, the driver core only enforces dependencies between devices
> +that are borne out of a parent/child relationship within the device
> +hierarchy: When suspending, resuming or shutting down the system, devices
> +are ordered based on this relationship, i.e. children are always suspended
> +before their parent, and the parent is always resumed before its children.
> +
> +Sometimes there is a need to represent device dependencies beyond the
> +mere parent/child relationship, e.g. between siblings, and have the
> +driver core automatically take care of them.
> +
> +Secondly, the driver core by default does not enforce any driver presence
> +dependencies, i.e. that one device must be bound to a driver before
> +another one can probe or function correctly.
> +
> +Often these two dependency types come together, so a device depends on
> +another one both with regards to driver presence *and* with regards to
> +suspend/resume and shutdown ordering.
> +
> +Device links allow representation of such dependencies in the driver core.
> +
> +In its standard form, a device link combines *both* dependency types:
> +It guarantees correct suspend/resume and shutdown ordering between a
> +"supplier" device and its "consumer" devices, and it guarantees driver
> +presence on the supplier: The consumer devices are not probed before the
> +supplier is bound to a driver, and they're unbound before the supplier
> +is unbound.
> +
> +When driver presence on the supplier is irrelevant and only correct
> +suspend/resume and shutdown ordering is needed, the device link may
> +simply be set up with the DEVICE_LINK_STATELESS flag.
> +
> +A driver presence dependency between parent and child, i.e. within the
> +regular device hierarchy, could in principle also be represented in the
> +driver core using a device link.
> +
> +If a device link is set up with the DEVICE_LINK_AUTOREMOVE flag, it is
> +automatically purged when the consumer fails to probe or later unbinds.
> +This is handy when adding a device link from the consumer's ->probe hook,
> +as it obviates the need to delete the link in the ->remove hook or in
> +the error path of the ->probe hook.
> +
> +
> +State machine
> +=============
> +
> +"""
> + .=============================.
> + | |
> + v |
> +DORMANT <=> AVAILABLE <=> CONSUMER_PROBE => ACTIVE
> + ^ |
> + | |
> + '============ SUPPLIER_UNBIND <============'
> +"""
> +
> +* The initial state of a device link is passed in to device_link_add().
> + If the link is created before any devices are probed, it must be set to
> + DEVICE_LINK_DORMANT.
> +
> +* When a supplier device is bound to a driver, links to its consumers
> + progress to DEVICE_LINK_AVAILABLE.
> + (Call to device_links_driver_bound() from driver_bound().)
> +
> +* Before a consumer device is probed, presence of supplier drivers is
> + verified by checking that links to suppliers are in DEVICE_LINK_AVAILABLE
> + state. The state of the links is updated to DEVICE_LINK_CONSUMER_PROBE.
> + (Call to device_links_check_suppliers() from driver_probe_device().)
> + This prevents the supplier from unbinding.
> + (Call to wait_for_device_probe() in device_links_unbind_consumers().)
> +
> +* If the probe fails, links to suppliers revert back to DEVICE_LINK_AVAILABLE.
> + (Call to device_links_no_driver() from really_probe().)
> +
> +* If the probe succeeds, links to suppliers progress to DEVICE_LINK_ACTIVE.
> + (Call of device_links_driver_bound() from driver_bound().)
> +
> +* When the consumer's driver is later on removed, links to suppliers revert
> + back to DEVICE_LINK_AVAILABLE.
> + (Call to device_links_no_driver() from __device_release_driver().)
> +
> +* Before a supplier's driver is removed, links to consumers that are not
> + bound to a driver are updated to DEVICE_LINK_SUPPLIER_UNBIND.
> + (Call to device_links_busy() from __device_release_driver().)
> + This prevents the consumers from binding.
> + (Call to device_links_check_suppliers() from driver_probe_device().)
> + Consumers that are bound are freed from their driver; consumers that are
> + probing are waited for until they are done.
> + (Call to device_links_unbind_consumers() from __device_release_driver().)
> + Once all links to consumers are in DEVICE_LINK_SUPPLIER_UNBIND state,
> + the supplier driver is released and the links revert to DEVICE_LINK_DORMANT.
> + (Call to device_links_driver_gone() from __device_release_driver().)
next prev parent reply other threads:[~2016-09-28 0:27 UTC|newest]
Thread overview: 138+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-08 21:25 [RFC/RFT][PATCH v2 0/7] Functional dependencies between devices Rafael J. Wysocki
2016-09-08 21:26 ` [RFC/RFT][PATCH v2 1/7] driver core: Add a wrapper around __device_release_driver() Rafael J. Wysocki
2016-09-08 21:27 ` [RFC/RFT][PATCH v2 2/7] driver core: Functional dependencies tracking support Rafael J. Wysocki
2016-09-09 8:25 ` Ulf Hansson
2016-09-09 12:06 ` Mark Brown
2016-09-09 14:13 ` Ulf Hansson
2016-09-15 1:11 ` Rafael J. Wysocki
2016-09-11 13:40 ` Lukas Wunner
2016-09-11 20:43 ` Lukas Wunner
2016-09-14 1:21 ` Rafael J. Wysocki
2016-09-14 8:28 ` Lukas Wunner
2016-09-14 13:17 ` Rafael J. Wysocki
2016-09-08 21:28 ` [RFC/RFT][PATCH v2 3/7] PM / sleep: Make async suspend/resume of devices use device links Rafael J. Wysocki
2016-09-10 13:31 ` Lukas Wunner
2016-09-10 22:12 ` Rafael J. Wysocki
2016-09-08 21:29 ` [RFC/RFT][PATCH v2 4/7] PM / runtime: Pass flags argument to __pm_runtime_disable() Rafael J. Wysocki
2016-09-08 21:29 ` [RFC/RFT][PATCH v2 5/7] PM / runtime: Flag to indicate PM sleep transitions in progress Rafael J. Wysocki
2016-09-12 14:07 ` Lukas Wunner
2016-09-12 21:25 ` Rafael J. Wysocki
2016-09-12 22:52 ` Lukas Wunner
2016-09-13 7:21 ` Marek Szyprowski
2016-09-13 23:59 ` Rafael J. Wysocki
2016-09-08 21:30 ` [RFC/RFT][PATCH v2 6/7] PM / runtime: Use device links Rafael J. Wysocki
2016-09-12 9:47 ` Lukas Wunner
2016-09-12 13:57 ` Rafael J. Wysocki
2016-09-14 1:19 ` Rafael J. Wysocki
2016-09-08 21:31 ` [RFC/RFT][PATCH v2 7/7] PM / runtime: Optimize the use of " Rafael J. Wysocki
2016-09-08 21:35 ` [RFC/RFT][PATCH v2 0/7] Functional dependencies between devices Rafael J. Wysocki
2016-09-10 11:39 ` Lukas Wunner
2016-09-10 22:04 ` Rafael J. Wysocki
2016-09-13 17:57 ` Lukas Wunner
2016-09-13 23:18 ` Rafael J. Wysocki
2016-09-18 12:39 ` Lukas Wunner
[not found] ` <CGME20160913095858eucas1p267ec2397c9e4577f94557e4a38498164@eucas1p2.samsung.com>
2016-09-13 9:58 ` Marek Szyprowski
2016-09-13 22:41 ` Rafael J. Wysocki
2016-09-18 11:23 ` Lukas Wunner
2016-09-15 22:03 ` [RFC/RFT][PATCH v3 0/5] " Rafael J. Wysocki
2016-09-15 22:04 ` [Resend][RFC/RFT][PATCH v3 1/5] driver core: Add a wrapper around __device_release_driver() Rafael J. Wysocki
2016-09-15 22:06 ` [RFC/RFT][PATCH v3 2/5] driver core: Functional dependencies tracking support Rafael J. Wysocki
2016-09-16 7:53 ` Marek Szyprowski
2016-09-16 12:06 ` Rafael J. Wysocki
2016-09-16 12:33 ` [Update][RFC/RFT][PATCH " Rafael J. Wysocki
2016-09-19 22:46 ` Lukas Wunner
2016-09-23 13:03 ` Lukas Wunner
2016-09-23 13:42 ` Rafael J. Wysocki
2016-09-26 16:51 ` Lukas Wunner
2016-09-27 12:16 ` Rafael J. Wysocki
2016-09-27 8:54 ` Lukas Wunner
2016-09-27 11:52 ` Rafael J. Wysocki
2016-09-28 10:43 ` Lukas Wunner
2016-09-28 11:31 ` Rafael J. Wysocki
2016-09-29 10:36 ` Lukas Wunner
2016-09-15 22:06 ` [RFC/RFT][PATCH v3 3/5] PM / sleep: Make async suspend/resume of devices use device links Rafael J. Wysocki
2016-09-15 22:07 ` [RFC/RFT][PATCH v3 4/5] PM / runtime: Use " Rafael J. Wysocki
2016-09-15 22:07 ` [RFC/RFT][PATCH v3 5/5] PM / runtime: Optimize the use of " Rafael J. Wysocki
2016-09-16 7:25 ` [RFC/RFT][PATCH v3 0/5] Functional dependencies between devices Marek Szyprowski
2016-09-16 7:57 ` Marek Szyprowski
2016-09-16 12:04 ` Rafael J. Wysocki
2016-09-27 12:34 ` Lukas Wunner
2016-09-28 0:33 ` Rafael J. Wysocki [this message]
2016-09-28 11:42 ` Lukas Wunner
2016-09-29 0:51 ` Rafael J. Wysocki
2016-11-15 18:50 ` Lukas Wunner
2016-09-29 0:24 ` [PATCH v4 " Rafael J. Wysocki
2016-09-29 0:25 ` [Resend][PATCH v4 1/5] driver core: Add a wrapper around __device_release_driver() Rafael J. Wysocki
2016-09-29 0:38 ` [PATCH v4 2/5] driver core: Functional dependencies tracking support Rafael J. Wysocki
2016-10-01 7:43 ` Lukas Wunner
2016-10-01 23:32 ` Rafael J. Wysocki
2016-09-29 0:38 ` [Resend][PATCH v4 3/5] PM / sleep: Make async suspend/resume of devices use device links Rafael J. Wysocki
2016-09-29 0:40 ` [PATCH v4 4/5] PM / runtime: Use " Rafael J. Wysocki
2016-09-29 0:41 ` [Rebase][PATCH v4 5/5] PM / runtime: Optimize the use of " Rafael J. Wysocki
2016-09-29 6:58 ` [PATCH v4 0/5] Functional dependencies between devices Marek Szyprowski
2016-09-29 12:27 ` Rafael J. Wysocki
2016-10-02 23:13 ` Lukas Wunner
2016-10-10 12:36 ` [PATCH v5 " Rafael J. Wysocki
2016-10-10 12:37 ` [Resend][PATCH v5 1/5] driver core: Add a wrapper around __device_release_driver() Rafael J. Wysocki
2016-10-10 12:51 ` [PATCH v5 2/5] driver core: Functional dependencies tracking support Rafael J. Wysocki
2016-10-26 11:19 ` Lukas Wunner
2016-10-27 15:25 ` Greg Kroah-Hartman
2016-10-28 9:57 ` Lukas Wunner
2016-11-07 21:22 ` Luis R. Rodriguez
2016-11-08 6:45 ` Greg Kroah-Hartman
2016-11-08 19:21 ` Luis R. Rodriguez
2016-11-08 19:43 ` Greg Kroah-Hartman
2016-11-08 20:58 ` Luis R. Rodriguez
2016-11-09 6:45 ` Greg Kroah-Hartman
2016-11-09 9:36 ` Andrzej Hajda
2016-11-09 9:41 ` Greg Kroah-Hartman
2016-11-13 16:58 ` Lukas Wunner
2016-11-10 0:43 ` Rafael J. Wysocki
2016-11-10 0:59 ` Luis R. Rodriguez
2016-11-10 7:14 ` Laurent Pinchart
2016-11-10 22:04 ` Luis R. Rodriguez
2016-11-10 22:40 ` Greg Kroah-Hartman
2016-11-11 0:08 ` Laurent Pinchart
2016-11-13 10:59 ` Greg Kroah-Hartman
2016-11-14 14:50 ` Luis R. Rodriguez
2016-11-14 8:15 ` Geert Uytterhoeven
2016-11-10 8:46 ` Geert Uytterhoeven
2016-11-10 22:12 ` Luis R. Rodriguez
2016-10-27 15:32 ` Greg Kroah-Hartman
2016-11-07 21:39 ` Luis R. Rodriguez
2016-11-10 1:07 ` Rafael J. Wysocki
2016-11-10 7:05 ` Laurent Pinchart
2016-11-10 23:09 ` Luis R. Rodriguez
2016-11-13 17:34 ` Lukas Wunner
2016-11-14 13:48 ` Luis R. Rodriguez
2016-11-14 15:48 ` Lukas Wunner
2016-11-14 16:00 ` Luis R. Rodriguez
2016-10-10 12:54 ` [PATCH v5 3/5] PM / sleep: Make async suspend/resume of devices use device links Rafael J. Wysocki
2016-10-10 12:56 ` [PATCH v5 4/5] PM / runtime: Use " Rafael J. Wysocki
2016-10-20 13:17 ` [Update][PATCH " Rafael J. Wysocki
2016-10-10 12:57 ` [Rebase][PATCH v5 5/5] PM / runtime: Optimize the use of " Rafael J. Wysocki
2016-10-18 10:46 ` [PATCH v5 0/5] Functional dependencies between devices Marek Szyprowski
2016-10-19 11:57 ` Rafael J. Wysocki
2016-10-20 10:21 ` Marek Szyprowski
2016-10-20 12:54 ` Rafael J. Wysocki
2016-10-27 15:32 ` Greg Kroah-Hartman
[not found] ` <5811F0CF.5000204@huawei.com>
2016-10-28 9:39 ` Lukas Wunner
2016-11-02 20:55 ` Hanjun Guo
2016-10-30 16:22 ` [PATCH v6 " Rafael J. Wysocki
2016-10-30 16:28 ` [Resend][PATCH v6 3/5] PM / sleep: Make async suspend/resume of devices use device links Rafael J. Wysocki
2016-10-30 16:29 ` [Resend][PATCH v6 1/5] driver core: Add a wrapper around __device_release_driver() Rafael J. Wysocki
2016-10-30 16:32 ` [PATCH v6 2/5] driver core: Functional dependencies tracking support Rafael J. Wysocki
2016-10-30 16:32 ` [PATCH v6 4/5] PM / runtime: Use device links Rafael J. Wysocki
2016-12-18 14:01 ` Lukas Wunner
2016-12-18 15:53 ` Rafael J. Wysocki
2016-12-18 16:37 ` Lukas Wunner
2016-12-19 12:38 ` Rafael J. Wysocki
2016-10-30 16:32 ` [Resend][PATCH v6 5/5] PM / runtime: Optimize the use of " Rafael J. Wysocki
2016-10-30 16:40 ` [PATCH v6 0/5] Functional dependencies between devices Rafael J. Wysocki
2016-10-31 17:47 ` Greg Kroah-Hartman
2016-11-01 3:50 ` Rafael J. Wysocki
2016-11-02 7:58 ` Marek Szyprowski
2016-11-05 12:10 ` Greg Kroah-Hartman
2016-11-07 21:15 ` Luis R. Rodriguez
2016-11-08 6:36 ` Marek Szyprowski
2016-11-08 20:14 ` Luis R. Rodriguez
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