diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-usb | 18 | ||||
| -rw-r--r-- | Documentation/driver-model/driver.txt | 4 | ||||
| -rw-r--r-- | Documentation/filesystems/sysfs.txt | 12 | ||||
| -rw-r--r-- | Documentation/power/runtime_pm.txt | 223 | ||||
| -rw-r--r-- | Documentation/powerpc/dts-bindings/fsl/mpic.txt | 42 | ||||
| -rw-r--r-- | Documentation/sound/alsa/HD-Audio-Models.txt | 1 | ||||
| -rw-r--r-- | Documentation/stable_kernel_rules.txt | 24 | ||||
| -rw-r--r-- | Documentation/trace/events-kmem.txt | 14 | ||||
| -rw-r--r-- | Documentation/usb/power-management.txt | 41 |
9 files changed, 242 insertions, 137 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb index deb6b489e4e5..a07c0f366f91 100644 --- a/Documentation/ABI/testing/sysfs-bus-usb +++ b/Documentation/ABI/testing/sysfs-bus-usb @@ -21,25 +21,27 @@ Contact: Alan Stern <stern@rowland.harvard.edu> Description: Each USB device directory will contain a file named power/level. This file holds a power-level setting for - the device, one of "on", "auto", or "suspend". + the device, either "on" or "auto". "on" means that the device is not allowed to autosuspend, although normal suspends for system sleep will still be honored. "auto" means the device will autosuspend and autoresume in the usual manner, according to the - capabilities of its driver. "suspend" means the device - is forced into a suspended state and it will not autoresume - in response to I/O requests. However remote-wakeup requests - from the device may still be enabled (the remote-wakeup - setting is controlled separately by the power/wakeup - attribute). + capabilities of its driver. During normal use, devices should be left in the "auto" - level. The other levels are meant for administrative uses. + level. The "on" level is meant for administrative uses. If you want to suspend a device immediately but leave it free to wake up in response to I/O requests, you should write "0" to power/autosuspend. + Device not capable of proper suspend and resume should be + left in the "on" level. Although the USB spec requires + devices to support suspend/resume, many of them do not. + In fact so many don't that by default, the USB core + initializes all non-hub devices in the "on" level. Some + drivers may change this setting when they are bound. + What: /sys/bus/usb/devices/.../power/persist Date: May 2007 KernelVersion: 2.6.23 diff --git a/Documentation/driver-model/driver.txt b/Documentation/driver-model/driver.txt index 60120fb3b961..d2cd6fb8ba9e 100644 --- a/Documentation/driver-model/driver.txt +++ b/Documentation/driver-model/driver.txt @@ -226,5 +226,5 @@ struct driver_attribute driver_attr_debug; This can then be used to add and remove the attribute from the driver's directory using: -int driver_create_file(struct device_driver *, struct driver_attribute *); -void driver_remove_file(struct device_driver *, struct driver_attribute *); +int driver_create_file(struct device_driver *, const struct driver_attribute *); +void driver_remove_file(struct device_driver *, const struct driver_attribute *); diff --git a/Documentation/filesystems/sysfs.txt b/Documentation/filesystems/sysfs.txt index b245d524d568..931c806642c5 100644 --- a/Documentation/filesystems/sysfs.txt +++ b/Documentation/filesystems/sysfs.txt @@ -91,8 +91,8 @@ struct device_attribute { const char *buf, size_t count); }; -int device_create_file(struct device *, struct device_attribute *); -void device_remove_file(struct device *, struct device_attribute *); +int device_create_file(struct device *, const struct device_attribute *); +void device_remove_file(struct device *, const struct device_attribute *); It also defines this helper for defining device attributes: @@ -316,8 +316,8 @@ DEVICE_ATTR(_name, _mode, _show, _store); Creation/Removal: -int device_create_file(struct device *device, struct device_attribute * attr); -void device_remove_file(struct device * dev, struct device_attribute * attr); +int device_create_file(struct device *dev, const struct device_attribute * attr); +void device_remove_file(struct device *dev, const struct device_attribute * attr); - bus drivers (include/linux/device.h) @@ -358,7 +358,7 @@ DRIVER_ATTR(_name, _mode, _show, _store) Creation/Removal: -int driver_create_file(struct device_driver *, struct driver_attribute *); -void driver_remove_file(struct device_driver *, struct driver_attribute *); +int driver_create_file(struct device_driver *, const struct driver_attribute *); +void driver_remove_file(struct device_driver *, const struct driver_attribute *); diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index 4a3109b28847..356fd86f4ea8 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -42,80 +42,81 @@ struct dev_pm_ops { ... }; -The ->runtime_suspend() callback is executed by the PM core for the bus type of -the device being suspended. The bus type's callback is then _entirely_ -_responsible_ for handling the device as appropriate, which may, but need not -include executing the device driver's own ->runtime_suspend() callback (from the +The ->runtime_suspend(), ->runtime_resume() and ->runtime_idle() callbacks are +executed by the PM core for either the bus type, or device type (if the bus +type's callback is not defined), or device class (if the bus type's and device +type's callbacks are not defined) of given device. The bus type, device type +and device class callbacks are referred to as subsystem-level callbacks in what +follows. + +The subsystem-level suspend callback is _entirely_ _responsible_ for handling +the suspend of the device as appropriate, which may, but need not include +executing the device driver's own ->runtime_suspend() callback (from the PM core's point of view it is not necessary to implement a ->runtime_suspend() -callback in a device driver as long as the bus type's ->runtime_suspend() knows -what to do to handle the device). +callback in a device driver as long as the subsystem-level suspend callback +knows what to do to handle the device). - * Once the bus type's ->runtime_suspend() callback has completed successfully + * Once the subsystem-level suspend callback has completed successfully for given device, the PM core regards the device as suspended, which need not mean that the device has been put into a low power state. It is supposed to mean, however, that the device will not process data and will - not communicate with the CPU(s) and RAM until its bus type's - ->runtime_resume() callback is executed for it. The run-time PM status of - a device after successful execution of its bus type's ->runtime_suspend() - callback is 'suspended'. - - * If the bus type's ->runtime_suspend() callback returns -EBUSY or -EAGAIN, - the device's run-time PM status is supposed to be 'active', which means that - the device _must_ be fully operational afterwards. - - * If the bus type's ->runtime_suspend() callback returns an error code - different from -EBUSY or -EAGAIN, the PM core regards this as a fatal - error and will refuse to run the helper functions described in Section 4 - for the device, until the status of it is directly set either to 'active' - or to 'suspended' (the PM core provides special helper functions for this - purpose). - -In particular, if the driver requires remote wakeup capability for proper -functioning and device_run_wake() returns 'false' for the device, then -->runtime_suspend() should return -EBUSY. On the other hand, if -device_run_wake() returns 'true' for the device and the device is put -into a low power state during the execution of its bus type's -->runtime_suspend(), it is expected that remote wake-up (i.e. hardware mechanism -allowing the device to request a change of its power state, such as PCI PME) -will be enabled for the device. Generally, remote wake-up should be enabled -for all input devices put into a low power state at run time. - -The ->runtime_resume() callback is executed by the PM core for the bus type of -the device being woken up. The bus type's callback is then _entirely_ -_responsible_ for handling the device as appropriate, which may, but need not -include executing the device driver's own ->runtime_resume() callback (from the -PM core's point of view it is not necessary to implement a ->runtime_resume() -callback in a device driver as long as the bus type's ->runtime_resume() knows -what to do to handle the device). - - * Once the bus type's ->runtime_resume() callback has completed successfully, - the PM core regards the device as fully operational, which means that the - device _must_ be able to complete I/O operations as needed. The run-time - PM status of the device is then 'active'. - - * If the bus type's ->runtime_resume() callback returns an error code, the PM - core regards this as a fatal error and will refuse to run the helper - functions described in Section 4 for the device, until its status is - directly set either to 'active' or to 'suspended' (the PM core provides - special helper functions for this purpose). - -The ->runtime_idle() callback is executed by the PM core for the bus type of -given device whenever the device appears to be idle, which is indicated to the -PM core by two counters, the device's usage counter and the counter of 'active' -children of the device. + not communicate with the CPU(s) and RAM until the subsystem-level resume + callback is executed for it. The run-time PM status of a device after + successful execution of the subsystem-level suspend callback is 'suspended'. + + * If the subsystem-level suspend callback returns -EBUSY or -EAGAIN, + the device's run-time PM status is 'active', which means that the device + _must_ be fully operational afterwards. + + * If the subsystem-level suspend callback returns an error code different + from -EBUSY or -EAGAIN, the PM core regards this as a fatal error and will + refuse to run the helper functions described in Section 4 for the device, + until the status of it is directly set either to 'active', or to 'suspended' + (the PM core provides special helper functions for this purpose). + +In particular, if the driver requires remote wake-up capability (i.e. hardware +mechanism allowing the device to request a change of its power state, such as +PCI PME) for proper functioning and device_run_wake() returns 'false' for the +device, then ->runtime_suspend() should return -EBUSY. On the other hand, if +device_run_wake() returns 'true' for the device and the device is put into a low +power state during the execution of the subsystem-level suspend callback, it is +expected that remote wake-up will be enabled for the device. Generally, remote +wake-up should be enabled for all input devices put into a low power state at +run time. + +The subsystem-level resume callback is _entirely_ _responsible_ for handling the +resume of the device as appropriate, which may, but need not include executing +the device driver's own ->runtime_resume() callback (from the PM core's point of +view it is not necessary to implement a ->runtime_resume() callback in a device +driver as long as the subsystem-level resume callback knows what to do to handle +the device). + + * Once the subsystem-level resume callback has completed successfully, the PM + core regards the device as fully operational, which means that the device + _must_ be able to complete I/O operations as needed. The run-time PM status + of the device is then 'active'. + + * If the subsystem-level resume callback returns an error code, the PM core + regards this as a fatal error and will refuse to run the helper functions + described in Section 4 for the device, until its status is directly set + either to 'active' or to 'suspended' (the PM core provides special helper + functions for this purpose). + +The subsystem-level idle callback is executed by the PM core whenever the device +appears to be idle, which is indicated to the PM core by two counters, the +device's usage counter and the counter of 'active' children of the device. * If any of these counters is decreased using a helper function provided by the PM core and it turns out to be equal to zero, the other counter is checked. If that counter also is equal to zero, the PM core executes the - device bus type's ->runtime_idle() callback (with the device as an - argument). + subsystem-level idle callback with the device as an argument. -The action performed by a bus type's ->runtime_idle() callback is totally -dependent on the bus type in question, but the expected and recommended action -is to check if the device can be suspended (i.e. if all of the conditions -necessary for suspending the device are satisfied) and to queue up a suspend -request for the device in that case. The value returned by this callback is -ignored by the PM core. +The action performed by a subsystem-level idle callback is totally dependent on +the subsystem in question, but the expected and recommended action is to check +if the device can be suspended (i.e. if all of the conditions necessary for +suspending the device are satisfied) and to queue up a suspend request for the +device in that case. The value returned by this callback is ignored by the PM +core. The helper functions provided by the PM core, described in Section 4, guarantee that the following constraints are met with respect to the bus type's run-time @@ -238,41 +239,41 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: removing the device from device hierarchy int pm_runtime_idle(struct device *dev); - - execute ->runtime_idle() for the device's bus type; returns 0 on success - or error code on failure, where -EINPROGRESS means that ->runtime_idle() - is already being executed + - execute the subsystem-level idle callback for the device; returns 0 on + success or error code on failure, where -EINPROGRESS means that + ->runtime_idle() is already being executed int pm_runtime_suspend(struct device *dev); - - execute ->runtime_suspend() for the device's bus type; returns 0 on + - execute the subsystem-level suspend callback for the device; returns 0 on success, 1 if the device's run-time PM status was already 'suspended', or error code on failure, where -EAGAIN or -EBUSY means it is safe to attempt to suspend the device again in future int pm_runtime_resume(struct device *dev); - - execute ->runtime_resume() for the device's bus type; returns 0 on + - execute the subsystem-leve resume callback for the device; returns 0 on success, 1 if the device's run-time PM status was already 'active' or error code on failure, where -EAGAIN means it may be safe to attempt to resume the device again in future, but 'power.runtime_error' should be checked additionally int pm_request_idle(struct device *dev); - - submit a request to execute ->runtime_idle() for the device's bus type - (the request is represented by a work item in pm_wq); returns 0 on success - or error code if the request has not been queued up + - submit a request to execute the subsystem-level idle callback for the + device (the request is represented by a work item in pm_wq); returns 0 on + success or error code if the request has not been queued up int pm_schedule_suspend(struct device *dev, unsigned int delay); - - schedule the execution of ->runtime_suspend() for the device's bus type - in future, where 'delay' is the time to wait before queuing up a suspend - work item in pm_wq, in milliseconds (if 'delay' is zero, the work item is - queued up immediately); returns 0 on success, 1 if the device's PM + - schedule the execution of the subsystem-level suspend callback for the + device in future, where 'delay' is the time to wait before queuing up a + suspend work item in pm_wq, in milliseconds (if 'delay' is zero, the work + item is queued up immediately); returns 0 on success, 1 if the device's PM run-time status was already 'suspended', or error code if the request hasn't been scheduled (or queued up if 'delay' is 0); if the execution of ->runtime_suspend() is already scheduled and not yet expired, the new value of 'delay' will be used as the time to wait int pm_request_resume(struct device *dev); - - submit a request to execute ->runtime_resume() for the device's bus type - (the request is represented by a work item in pm_wq); returns 0 on + - submit a request to execute the subsystem-level resume callback for the + device (the request is represented by a work item in pm_wq); returns 0 on success, 1 if the device's run-time PM status was already 'active', or error code if the request hasn't been queued up @@ -303,12 +304,12 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: run-time PM callbacks described in Section 2 int pm_runtime_disable(struct device *dev); - - prevent the run-time PM helper functions from running the device bus - type's run-time PM callbacks, make sure that all of the pending run-time - PM operations on the device are either completed or canceled; returns - 1 if there was a resume request pending and it was necessary to execute - ->runtime_resume() for the device's bus type to satisfy that request, - otherwise 0 is returned + - prevent the run-time PM helper functions from running subsystem-level + run-time PM callbacks for the device, make sure that all of the pending + run-time PM operations on the device are either completed or canceled; + returns 1 if there was a resume request pending and it was necessary to + execute the subsystem-level resume callback for the device to satisfy that + request, otherwise 0 is returned void pm_suspend_ignore_children(struct device *dev, bool enable); - set/unset the power.ignore_children flag of the device @@ -378,5 +379,55 @@ pm_runtime_suspend() or pm_runtime_idle() or their asynchronous counterparts, they will fail returning -EAGAIN, because the device's usage counter is incremented by the core before executing ->probe() and ->remove(). Still, it may be desirable to suspend the device as soon as ->probe() or ->remove() has -finished, so the PM core uses pm_runtime_idle_sync() to invoke the device bus -type's ->runtime_idle() callback at that time. +finished, so the PM core uses pm_runtime_idle_sync() to invoke the +subsystem-level idle callback for the device at that time. + +6. Run-time PM and System Sleep + +Run-time PM and system sleep (i.e., system suspend and hibernation, also known +as suspend-to-RAM and suspend-to-disk) interact with each other in a couple of +ways. If a device is active when a system sleep starts, everything is +straightforward. But what should happen if the device is already suspended? + +The device may have different wake-up settings for run-time PM and system sleep. +For example, remote wake-up may be enabled for run-time suspend but disallowed +for system sleep (device_may_wakeup(dev) returns 'false'). When this happens, +the subsystem-level system suspend callback is responsible for changing the +device's wake-up setting (it may leave that to the device driver's system +suspend routine). It may be necessary to resume the device and suspend it again +in order to do so. The same is true if the driver uses different power levels +or other settings for run-time suspend and system sleep. + +During system resume, devices generally should be brought back to full power, +even if they were suspended before the system sleep began. There are several +reasons for this, including: + + * The device might need to switch power levels, wake-up settings, etc. + + * Remote wake-up events might have been lost by the firmware. + + * The device's children may need the device to be at full power in order + to resume themselves. + + * The driver's idea of the device state may not agree with the device's + physical state. This can happen during resume from hibernation. + + * The device might need to be reset. + + * Even though the device was suspended, if its usage counter was > 0 then most + likely it would need a run-time resume in the near future anyway. + + * Always going back to full power is simplest. + +If the device was suspended before the sleep began, then its run-time PM status +will have to be updated to reflect the actual post-system sleep status. The way +to do this is: + + pm_runtime_disable(dev); + pm_runtime_set_active(dev); + pm_runtime_enable(dev); + +The PM core always increments the run-time usage counter before calling the +->prepare() callback and decrements it after calling the ->complete() callback. +Hence disabling run-time PM temporarily like this will not cause any run-time +suspend callbacks to be lost. diff --git a/Documentation/powerpc/dts-bindings/fsl/mpic.txt b/Documentation/powerpc/dts-bindings/fsl/mpic.txt new file mode 100644 index 000000000000..71e39cf3215b --- /dev/null +++ b/Documentation/powerpc/dts-bindings/fsl/mpic.txt @@ -0,0 +1,42 @@ +* OpenPIC and its interrupt numbers on Freescale's e500/e600 cores + +The OpenPIC specification does not specify which interrupt source has to +become which interrupt number. This is up to the software implementation +of the interrupt controller. The only requirement is that every +interrupt source has to have an unique interrupt number / vector number. +To accomplish this the current implementation assigns the number zero to +the first source, the number one to the second source and so on until +all interrupt sources have their unique number. +Usually the assigned vector number equals the interrupt number mentioned +in the documentation for a given core / CPU. This is however not true +for the e500 cores (MPC85XX CPUs) where the documentation distinguishes +between internal and external interrupt sources and starts counting at +zero for both of them. + +So what to write for external interrupt source X or internal interrupt +source Y into the device tree? Here is an example: + +The memory map for the interrupt controller in the MPC8544[0] shows, +that the first interrupt source starts at 0x5_0000 (PIC Register Address +Map-Interrupt Source Configuration Registers). This source becomes the +number zero therefore: + External interrupt 0 = interrupt number 0 + External interrupt 1 = interrupt number 1 + External interrupt 2 = interrupt number 2 + ... +Every interrupt number allocates 0x20 bytes register space. So to get +its number it is sufficient to shift the lower 16bits to right by five. +So for the external interrupt 10 we have: + 0x0140 >> 5 = 10 + +After the external sources, the internal sources follow. The in core I2C +controller on the MPC8544 for instance has the internal source number +27. Oo obtain its interrupt number we take the lower 16bits of its memory +address (0x5_0560) and shift it right: + 0x0560 >> 5 = 43 + +Therefore the I2C device node for the MPC8544 CPU has to have the +interrupt number 43 specified in the device tree. + +[0] MPC8544E PowerQUICCTM III, Integrated Host Processor Family Reference Manual + MPC8544ERM Rev. 1 10/2007 diff --git a/Documentation/sound/alsa/HD-Audio-Models.txt b/Documentation/sound/alsa/HD-Audio-Models.txt index e93affff3af8..e72cee9e2a71 100644 --- a/Documentation/sound/alsa/HD-Audio-Models.txt +++ b/Documentation/sound/alsa/HD-Audio-Models.txt @@ -403,4 +403,5 @@ STAC9872 Cirrus Logic CS4206/4207 ======================== mbp55 MacBook Pro 5,5 + imac27 IMac 27 Inch auto BIOS setup (default) diff --git a/Documentation/stable_kernel_rules.txt b/Documentation/stable_kernel_rules.txt index a452227361b1..5effa5bd993b 100644 --- a/Documentation/stable_kernel_rules.txt +++ b/Documentation/stable_kernel_rules.txt @@ -26,13 +26,33 @@ Procedure for submitting patches to the -stable tree: - Send the patch, after verifying that it follows the above rules, to stable@kernel.org. + - To have the patch automatically included in the stable tree, add the + the tag + Cc: stable@kernel.org + in the sign-off area. Once the patch is merged it will be applied to + the stable tree without anything else needing to be done by the author + or subsystem maintainer. + - If the patch requires other patches as prerequisites which can be + cherry-picked than this can be specified in the following format in + the sign-off area: + + Cc: <stable@kernel.org> # .32.x: a1f84a3: sched: Check for idle + Cc: <stable@kernel.org> # .32.x: 1b9508f: sched: Rate-limit newidle + Cc: <stable@kernel.org> # .32.x: fd21073: sched: Fix affinity logic + Cc: <stable@kernel.org> # .32.x + Signed-off-by: Ingo Molnar <mingo@elte.hu> + + The tag sequence has the meaning of: + git cherry-pick a1f84a3 + git cherry-pick 1b9508f + git cherry-pick fd21073 + git cherry-pick <this commit> + - The sender will receive an ACK when the patch has been accepted into the queue, or a NAK if the patch is rejected. This response might take a few days, according to the developer's schedules. - If accepted, the patch will be added to the -stable queue, for review by other developers and by the relevant subsystem maintainer. - - If the stable@kernel.org address is added to a patch, when it goes into - Linus's tree it will automatically be emailed to the stable team. - Security patches should not be sent to this alias, but instead to the documented security@kernel.org address. diff --git a/Documentation/trace/events-kmem.txt b/Documentation/trace/events-kmem.txt index 6ef2a8652e17..aa82ee4a5a87 100644 --- a/Documentation/trace/events-kmem.txt +++ b/Documentation/trace/events-kmem.txt @@ -1,7 +1,7 @@ Subsystem Trace Points: kmem -The tracing system kmem captures events related to object and page allocation -within the kernel. Broadly speaking there are four major subheadings. +The kmem tracing system captures events related to object and page allocation +within the kernel. Broadly speaking there are five major subheadings. o Slab allocation of small objects of unknown type (kmalloc) o Slab allocation of small objects of known type @@ -9,7 +9,7 @@ within the kernel. Broadly speaking there are four major subheadings. o Per-CPU Allocator Activity o External Fragmentation -This document will describe what each of the tracepoints are and why they +This document describes what each of the tracepoints is and why they might be useful. 1. Slab allocation of small objects of unknown type @@ -34,7 +34,7 @@ kmem_cache_free call_site=%lx ptr=%p These events are similar in usage to the kmalloc-related events except that it is likely easier to pin the event down to a specific cache. At the time of writing, no information is available on what slab is being allocated from, -but the call_site can usually be used to extrapolate that information +but the call_site can usually be used to extrapolate that information. 3. Page allocation ================== @@ -80,9 +80,9 @@ event indicating whether it is for a percpu_refill or not. When the per-CPU list is too full, a number of pages are freed, each one which triggers a mm_page_pcpu_drain event. -The individual nature of the events are so that pages can be tracked +The individual nature of the events is so that pages can be tracked between allocation and freeing. A number of drain or refill pages that occur -consecutively imply the zone->lock being taken once. Large amounts of PCP +consecutively imply the zone->lock being taken once. Large amounts of per-CPU refills and drains could imply an imbalance between CPUs where too much work is being concentrated in one place. It could also indicate that the per-CPU lists should be a larger size. Finally, large amounts of refills on one CPU @@ -102,6 +102,6 @@ is important. Large numbers of this event implies that memory is fragmenting and high-order allocations will start failing at some time in the future. One -means of reducing the occurange of this event is to increase the size of +means of reducing the occurrence of this event is to increase the size of min_free_kbytes in increments of 3*pageblock_size*nr_online_nodes where pageblock_size is usually the size of the default hugepage size. diff --git a/Documentation/usb/power-management.txt b/Documentation/usb/power-management.txt index c7c1dc2f8017..3bf6818c8cf5 100644 --- a/Documentation/usb/power-management.txt +++ b/Documentation/usb/power-management.txt @@ -71,12 +71,10 @@ being accessed through sysfs, then it definitely is idle. Forms of dynamic PM ------------------- -Dynamic suspends can occur in two ways: manual and automatic. -"Manual" means that the user has told the kernel to suspend a device, -whereas "automatic" means that the kernel has decided all by itself to -suspend a device. Automatic suspend is called "autosuspend" for -short. In general, a device won't be autosuspended unless it has been -idle for some minimum period of time, the so-called idle-delay time. +Dynamic suspends occur when the kernel decides to suspend an idle +device. This is called "autosuspend" for short. In general, a device +won't be autosuspended unless it has been idle for some minimum period +of time, the so-called idle-delay time. Of course, nothing the kernel does on its own initiative should prevent the computer or its devices from working properly. If a @@ -96,10 +94,11 @@ idle. We can categorize power management events in two broad classes: external and internal. External events are those triggered by some agent outside the USB stack: system suspend/resume (triggered by -userspace), manual dynamic suspend/resume (also triggered by -userspace), and remote wakeup (triggered by the device). Internal -events are those triggered within the USB stack: autosuspend and -autoresume. +userspace), manual dynamic resume (also triggered by userspace), and +remote wakeup (triggered by the device). Internal events are those +triggered within the USB stack: autosuspend and autoresume. Note that +all dynamic suspend events are internal; external agents are not +allowed to issue dynamic suspends. The user interface for dynamic PM @@ -145,9 +144,9 @@ relevant attribute files are: wakeup, level, and autosuspend. number of seconds the device should remain idle before the kernel will autosuspend it (the idle-delay time). The default is 2. 0 means to autosuspend as soon as - the device becomes idle, and -1 means never to - autosuspend. You can write a number to the file to - change the autosuspend idle-delay time. + the device becomes idle, and negative values mean + never to autosuspend. You can write a number to the + file to change the autosuspend idle-delay time. Writing "-1" to power/autosuspend and writing "on" to power/level do essentially the same thing -- they both prevent the device from being @@ -377,9 +376,9 @@ the device hasn't been idle for long enough, a delayed workqueue routine is automatically set up to carry out the operation when the autosuspend idle-delay has expired. -Autoresume attempts also can fail. This will happen if power/level is -set to "suspend" or if the device doesn't manage to resume properly. -Unlike autosuspend, there's no delay for an autoresume. +Autoresume attempts also can fail, although failure would mean that +the device is no longer present or operating properly. Unlike +autosuspend, there's no delay for an autoresume. Other parts of the driver interface @@ -527,13 +526,3 @@ succeed, it may still remain active and thus cause the system to resume as soon as the system suspend is complete. Or the remote wakeup may fail and get lost. Which outcome occurs depends on timing and on the hardware and firmware design. - -More interestingly, a device might undergo a manual resume or -autoresume during system suspend. With current kernels this shouldn't -happen, because manual resumes must be initiated by userspace and -autoresumes happen in response to I/O requests, but all user processes -and I/O should be quiescent during a system suspend -- thanks to the -freezer. However there are plans to do away with the freezer, which -would mean these things would become possible. If and when this comes -about, the USB core will carefully arrange matters so that either type -of resume will block until the entire system has resumed. |