From cde9070d9970eef1f7ec2360586c802a16230ad8 Mon Sep 17 00:00:00 2001 From: hc <hc@nodka.com> Date: Fri, 10 May 2024 07:43:50 +0000 Subject: [PATCH] rtl88x2CE_WiFi_linux driver --- kernel/Documentation/driver-api/device_link.rst | 33 +++++++++++++++++++++++---------- 1 files changed, 23 insertions(+), 10 deletions(-) diff --git a/kernel/Documentation/driver-api/device_link.rst b/kernel/Documentation/driver-api/device_link.rst index a3fe1ff..ee913ae 100644 --- a/kernel/Documentation/driver-api/device_link.rst +++ b/kernel/Documentation/driver-api/device_link.rst @@ -1,5 +1,4 @@ -.. |struct dev_pm_domain| replace:: :c:type:`struct dev_pm_domain <dev_pm_domain>` -.. |struct generic_pm_domain| replace:: :c:type:`struct generic_pm_domain <generic_pm_domain>` +.. _device_link: ============ Device links @@ -86,9 +85,10 @@ Two other flags are specifically targeted at use cases where the device link is added from the consumer's ``->probe`` callback: ``DL_FLAG_RPM_ACTIVE`` -can be specified to runtime resume the supplier upon addition of the -device link. ``DL_FLAG_AUTOREMOVE_CONSUMER`` causes the device link to be -automatically purged when the consumer fails to probe or later unbinds. +can be specified to runtime resume the supplier and prevent it from suspending +before the consumer is runtime suspended. ``DL_FLAG_AUTOREMOVE_CONSUMER`` +causes the device link to be automatically purged when the consumer fails to +probe or later unbinds. Similarly, when the device link is added from supplier's ``->probe`` callback, ``DL_FLAG_AUTOREMOVE_SUPPLIER`` causes the device link to be automatically @@ -121,6 +121,20 @@ to add them with the help of either :c:func:`device_link_del()` or :c:func:`device_link_remove()`. +Passing ``DL_FLAG_RPM_ACTIVE`` along with ``DL_FLAG_STATELESS`` to +:c:func:`device_link_add()` may cause the PM-runtime usage counter of the +supplier device to remain nonzero after a subsequent invocation of either +:c:func:`device_link_del()` or :c:func:`device_link_remove()` to remove the +device link returned by it. This happens if :c:func:`device_link_add()` is +called twice in a row for the same consumer-supplier pair without removing the +link between these calls, in which case allowing the PM-runtime usage counter +of the supplier to drop on an attempt to remove the link may cause it to be +suspended while the consumer is still PM-runtime-active and that has to be +avoided. [To work around this limitation it is sufficient to let the consumer +runtime suspend at least once, or call :c:func:`pm_runtime_set_suspended()` for +it with PM-runtime disabled, between the :c:func:`device_link_add()` and +:c:func:`device_link_del()` or :c:func:`device_link_remove()` calls.] + Sometimes drivers depend on optional resources. They are able to operate in a degraded mode (reduced feature set or performance) when those resources are not present. An example is an SPI controller that can use a DMA engine @@ -148,7 +162,7 @@ is the same as if the MMU was the parent of the master device. The fact that both devices share the same power domain would normally - suggest usage of a |struct dev_pm_domain| or |struct generic_pm_domain|, + suggest usage of a struct dev_pm_domain or struct generic_pm_domain, however these are not independent devices that happen to share a power switch, but rather the MMU device serves the busmaster device and is useless without it. A device link creates a synthetic hierarchical @@ -184,7 +198,7 @@ Alternatives ============ -* A |struct dev_pm_domain| can be used to override the bus, +* A struct dev_pm_domain can be used to override the bus, class or device type callbacks. It is intended for devices sharing a single on/off switch, however it does not guarantee a specific suspend/resume ordering, this needs to be implemented separately. @@ -193,7 +207,7 @@ suspended. Furthermore it cannot be used to enforce a specific shutdown ordering or a driver presence dependency. -* A |struct generic_pm_domain| is a lot more heavyweight than a +* A struct generic_pm_domain is a lot more heavyweight than a device link and does not allow for shutdown ordering or driver presence dependencies. It also cannot be used on ACPI systems. @@ -303,5 +317,4 @@ API === -.. kernel-doc:: drivers/base/core.c - :functions: device_link_add device_link_del device_link_remove +See device_link_add(), device_link_del() and device_link_remove(). -- Gitblit v1.6.2