diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/DocBook/Makefile | 2 | ||||
| -rw-r--r-- | Documentation/DocBook/s390-drivers.tmpl | 149 | ||||
| -rw-r--r-- | Documentation/filesystems/ntfs.txt | 4 | ||||
| -rw-r--r-- | Documentation/kernel-parameters.txt | 7 | ||||
| -rw-r--r-- | Documentation/s390/00-INDEX | 26 | ||||
| -rw-r--r-- | Documentation/s390/CommonIO | 51 | ||||
| -rw-r--r-- | Documentation/s390/cds.txt | 8 | ||||
| -rw-r--r-- | Documentation/usb/authorization.txt | 92 | ||||
| -rw-r--r-- | Documentation/usb/power-management.txt | 517 | ||||
| -rw-r--r-- | Documentation/usb/usb-serial.txt | 11 | ||||
| -rw-r--r-- | Documentation/usb/usbmon.txt | 9 |
11 files changed, 847 insertions, 29 deletions
diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile index 08687e45e19..1a7f53068ec 100644 --- a/Documentation/DocBook/Makefile +++ b/Documentation/DocBook/Makefile @@ -11,7 +11,7 @@ DOCBOOKS := wanbook.xml z8530book.xml mcabook.xml videobook.xml \ procfs-guide.xml writing_usb_driver.xml \ kernel-api.xml filesystems.xml lsm.xml usb.xml \ gadget.xml libata.xml mtdnand.xml librs.xml rapidio.xml \ - genericirq.xml + genericirq.xml s390-drivers.xml ### # The build process is as follows (targets): diff --git a/Documentation/DocBook/s390-drivers.tmpl b/Documentation/DocBook/s390-drivers.tmpl new file mode 100644 index 00000000000..254e769282a --- /dev/null +++ b/Documentation/DocBook/s390-drivers.tmpl @@ -0,0 +1,149 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" + "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []> + +<book id="s390drivers"> + <bookinfo> + <title>Writing s390 channel device drivers</title> + + <authorgroup> + <author> + <firstname>Cornelia</firstname> + <surname>Huck</surname> + <affiliation> + <address> + <email>cornelia.huck@de.ibm.com</email> + </address> + </affiliation> + </author> + </authorgroup> + + <copyright> + <year>2007</year> + <holder>IBM Corp.</holder> + </copyright> + + <legalnotice> + <para> + This documentation is free software; you can redistribute + it and/or modify it under the terms of the GNU General Public + License as published by the Free Software Foundation; either + version 2 of the License, or (at your option) any later + version. + </para> + + <para> + This program is distributed in the hope that it will be + useful, but WITHOUT ANY WARRANTY; without even the implied + warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. + See the GNU General Public License for more details. + </para> + + <para> + You should have received a copy of the GNU General Public + License along with this program; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, + MA 02111-1307 USA + </para> + + <para> + For more details see the file COPYING in the source + distribution of Linux. + </para> + </legalnotice> + </bookinfo> + +<toc></toc> + + <chapter id="intro"> + <title>Introduction</title> + <para> + This document describes the interfaces available for device drivers that + drive s390 based channel attached devices. This includes interfaces for + interaction with the hardware and interfaces for interacting with the + common driver core. Those interfaces are provided by the s390 common I/O + layer. + </para> + <para> + The document assumes a familarity with the technical terms associated + with the s390 channel I/O architecture. For a description of this + architecture, please refer to the "z/Architecture: Principles of + Operation", IBM publication no. SA22-7832. + </para> + <para> + While most I/O devices on a s390 system are typically driven through the + channel I/O mechanism described here, there are various other methods + (like the diag interface). These are out of the scope of this document. + </para> + <para> + Some additional information can also be found in the kernel source + under Documentation/s390/driver-model.txt. + </para> + </chapter> + <chapter id="ccw"> + <title>The ccw bus</title> + <para> + The ccw bus typically contains the majority of devices available to + a s390 system. Named after the channel command word (ccw), the basic + command structure used to address its devices, the ccw bus contains + so-called channel attached devices. They are addressed via subchannels, + visible on the css bus. A device driver, however, will never interact + with the subchannel directly, but only via the device on the ccw bus, + the ccw device. + </para> + <sect1 id="channelIO"> + <title>I/O functions for channel-attached devices</title> + <para> + Some hardware structures have been translated into C structures for use + by the common I/O layer and device drivers. For more information on + the hardware structures represented here, please consult the Principles + of Operation. + </para> +!Iinclude/asm-s390/cio.h + </sect1> + <sect1 id="ccwdev"> + <title>ccw devices</title> + <para> + Devices that want to initiate channel I/O need to attach to the ccw bus. + Interaction with the driver core is done via the common I/O layer, which + provides the abstractions of ccw devices and ccw device drivers. + </para> + <para> + The functions that initiate or terminate channel I/O all act upon a + ccw device structure. Device drivers must not bypass those functions + or strange side effects may happen. + </para> +!Iinclude/asm-s390/ccwdev.h +!Edrivers/s390/cio/device.c +!Edrivers/s390/cio/device_ops.c + </sect1> + <sect1 id="cmf"> + <title>The channel-measurement facility</title> + <para> + The channel-measurement facility provides a means to collect + measurement data which is made available by the channel subsystem + for each channel attached device. + </para> +!Iinclude/asm-s390/cmb.h +!Edrivers/s390/cio/cmf.c + </sect1> + </chapter> + + <chapter id="ccwgroup"> + <title>The ccwgroup bus</title> + <para> + The ccwgroup bus only contains artificial devices, created by the user. + Many networking devices (e.g. qeth) are in fact composed of several + ccw devices (like read, write and data channel for qeth). The + ccwgroup bus provides a mechanism to create a meta-device which + contains those ccw devices as slave devices and can be associated + with the netdevice. + </para> + <sect1 id="ccwgroupdevices"> + <title>ccw group devices</title> +!Iinclude/asm-s390/ccwgroup.h +!Edrivers/s390/cio/ccwgroup.c + </sect1> + </chapter> + +</book> diff --git a/Documentation/filesystems/ntfs.txt b/Documentation/filesystems/ntfs.txt index 8ee10ec8829..e79ee2db183 100644 --- a/Documentation/filesystems/ntfs.txt +++ b/Documentation/filesystems/ntfs.txt @@ -407,7 +407,7 @@ raiddev /dev/md0 device /dev/hda5 raid-disk 0 device /dev/hdb1 - raid-disl 1 + raid-disk 1 For linear raid, just change the raid-level above to "raid-level linear", for mirrors, change it to "raid-level 1", and for stripe sets with parity, change @@ -457,6 +457,8 @@ ChangeLog Note, a technical ChangeLog aimed at kernel hackers is in fs/ntfs/ChangeLog. +2.1.29: + - Fix a deadlock when mounting read-write. 2.1.28: - Fix a deadlock. 2.1.27: diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index bdddd3cd46d..912c57c2334 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1009,6 +1009,10 @@ and is between 256 and 4096 characters. It is defined in the file meye.*= [HW] Set MotionEye Camera parameters See Documentation/video4linux/meye.txt. + mfgpt_irq= [IA-32] Specify the IRQ to use for the + Multi-Function General Purpose Timers on AMD Geode + platforms. + mga= [HW,DRM] mousedev.tap_time= @@ -1160,6 +1164,9 @@ and is between 256 and 4096 characters. It is defined in the file nomce [X86-32] Machine Check Exception + nomfgpt [X86-32] Disable Multi-Function General Purpose + Timer usage (for AMD Geode machines). + noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops noreplace-smp [X86-32,SMP] Don't replace SMP instructions diff --git a/Documentation/s390/00-INDEX b/Documentation/s390/00-INDEX new file mode 100644 index 00000000000..3a2b96302ec --- /dev/null +++ b/Documentation/s390/00-INDEX @@ -0,0 +1,26 @@ +00-INDEX + - this file. +3270.ChangeLog + - ChangeLog for the UTS Global 3270-support patch (outdated). +3270.txt + - how to use the IBM 3270 display system support. +cds.txt + - s390 common device support (common I/O layer). +CommonIO + - common I/O layer command line parameters, procfs and debugfs entries +config3270.sh + - example configuration for 3270 devices. +DASD + - information on the DASD disk device driver. +Debugging390.txt + - hints for debugging on s390 systems. +driver-model.txt + - information on s390 devices and the driver model. +monreader.txt + - information on accessing the z/VM monitor stream from Linux. +s390dbf.txt + - information on using the s390 debug feature. +TAPE + - information on the driver for channel-attached tapes. +zfcpdump + - information on the s390 SCSI dump tool. diff --git a/Documentation/s390/CommonIO b/Documentation/s390/CommonIO index 22f82f21bc6..86320aa3fb0 100644 --- a/Documentation/s390/CommonIO +++ b/Documentation/s390/CommonIO @@ -1,5 +1,5 @@ -S/390 common I/O-Layer - command line parameters and /proc entries -================================================================== +S/390 common I/O-Layer - command line parameters, procfs and debugfs entries +============================================================================ Command line parameters ----------------------- @@ -7,9 +7,9 @@ Command line parameters * cio_msg = yes | no Determines whether information on found devices and sensed device - characteristics should be shown during startup, i. e. messages of the types - "Detected device 0.0.4711 on subchannel 0.0.0042" and "SenseID: Device - 0.0.4711 reports: ...". + characteristics should be shown during startup or when new devices are + found, i. e. messages of the types "Detected device 0.0.4711 on subchannel + 0.0.0042" and "SenseID: Device 0.0.4711 reports: ...". Default is off. @@ -26,8 +26,10 @@ Command line parameters An ignored device can be un-ignored later; see the "/proc entries"-section for details. - The devices must be given either as bus ids (0.0.abcd) or as hexadecimal - device numbers (0xabcd or abcd, for 2.4 backward compatibility). + The devices must be given either as bus ids (0.x.abcd) or as hexadecimal + device numbers (0xabcd or abcd, for 2.4 backward compatibility). If you + give a device number 0xabcd, it will be interpreted as 0.0.abcd. + You can use the 'all' keyword to ignore all devices. The '!' operator will cause the I/O-layer to _not_ ignore a device. The command line is parsed from left to right. @@ -81,31 +83,36 @@ Command line parameters will add 0.0.a000-0.0.accc and 0.0.af00-0.0.afff to the list of ignored devices. - The devices can be specified either by bus id (0.0.abcd) or, for 2.4 backward - compatibility, by the device number in hexadecimal (0xabcd or abcd). + The devices can be specified either by bus id (0.x.abcd) or, for 2.4 backward + compatibility, by the device number in hexadecimal (0xabcd or abcd). Device + numbers given as 0xabcd will be interpreted as 0.0.abcd. + +* For some of the information present in the /proc filesystem in 2.4 (namely, + /proc/subchannels and /proc/chpids), see driver-model.txt. + Information formerly in /proc/irq_count is now in /proc/interrupts. + +debugfs entries +--------------- -* /proc/s390dbf/cio_*/ (S/390 debug feature) +* /sys/kernel/debug/s390dbf/cio_*/ (S/390 debug feature) Some views generated by the debug feature to hold various debug outputs. - - /proc/s390dbf/cio_crw/sprintf + - /sys/kernel/debug/s390dbf/cio_crw/sprintf Messages from the processing of pending channel report words (machine check - handling), which will also show when CONFIG_DEBUG_CRW is defined. + handling). - - /proc/s390dbf/cio_msg/sprintf - Various debug messages from the common I/O-layer; generally, messages which - will also show when CONFIG_DEBUG_IO is defined. + - /sys/kernel/debug/s390dbf/cio_msg/sprintf + Various debug messages from the common I/O-layer, including messages + printed when cio_msg=yes. - - /proc/s390dbf/cio_trace/hex_ascii + - /sys/kernel/debug/s390dbf/cio_trace/hex_ascii Logs the calling of functions in the common I/O-layer and, if applicable, which subchannel they were called for, as well as dumps of some data structures (like irb in an error case). The level of logging can be changed to be more or less verbose by piping to - /proc/s390dbf/cio_*/level a number between 0 and 6; see the documentation on - the S/390 debug feature (Documentation/s390/s390dbf.txt) for details. - -* For some of the information present in the /proc filesystem in 2.4 (namely, - /proc/subchannels and /proc/chpids), see driver-model.txt. - Information formerly in /proc/irq_count is now in /proc/interrupts. + /sys/kernel/debug/s390dbf/cio_*/level a number between 0 and 6; see the + documentation on the S/390 debug feature (Documentation/s390/s390dbf.txt) + for details. diff --git a/Documentation/s390/cds.txt b/Documentation/s390/cds.txt index 58919d6a593..3081927cc2d 100644 --- a/Documentation/s390/cds.txt +++ b/Documentation/s390/cds.txt @@ -286,10 +286,10 @@ first: timeout value -EIO: the common I/O layer terminated the request due to an error state -If the concurrent sense flag in the extended status word in the irb is set, the -field irb->scsw.count describes the number of device specific sense bytes -available in the extended control word irb->scsw.ecw[0]. No device sensing by -the device driver itself is required. +If the concurrent sense flag in the extended status word (esw) in the irb is +set, the field erw.scnt in the esw describes the number of device specific +sense bytes available in the extended control word irb->scsw.ecw[]. No device +sensing by the device driver itself is required. The device interrupt handler can use the following definitions to investigate the primary unit check source coded in sense byte 0 : diff --git a/Documentation/usb/authorization.txt b/Documentation/usb/authorization.txt new file mode 100644 index 00000000000..2af40060949 --- /dev/null +++ b/Documentation/usb/authorization.txt @@ -0,0 +1,92 @@ + +Authorizing (or not) your USB devices to connect to the system + +(C) 2007 Inaky Perez-Gonzalez <inaky@linux.intel.com> Intel Corporation + +This feature allows you to control if a USB device can be used (or +not) in a system. This feature will allow you to implement a lock-down +of USB devices, fully controlled by user space. + +As of now, when a USB device is connected it is configured and +it's interfaces inmediately made available to the users. With this +modification, only if root authorizes the device to be configured will +then it be possible to use it. + +Usage: + +Authorize a device to connect: + +$ echo 1 > /sys/usb/devices/DEVICE/authorized + +Deauthorize a device: + +$ echo 0 > /sys/usb/devices/DEVICE/authorized + +Set new devices connected to hostX to be deauthorized by default (ie: +lock down): + +$ echo 0 > /sys/bus/devices/usbX/authorized_default + +Remove the lock down: + +$ echo 1 > /sys/bus/devices/usbX/authorized_default + +By default, Wired USB devices are authorized by default to +connect. Wireless USB hosts deauthorize by default all new connected +devices (this is so because we need to do an authentication phase +before authorizing). + + +Example system lockdown (lame) +----------------------- + +Imagine you want to implement a lockdown so only devices of type XYZ +can be connected (for example, it is a kiosk machine with a visible +USB port): + +boot up +rc.local -> + + for host in /sys/bus/devices/usb* + do + echo 0 > $host/authorized_default + done + +Hookup an script to udev, for new USB devices + + if device_is_my_type $DEV + then + echo 1 > $device_path/authorized + done + + +Now, device_is_my_type() is where the juice for a lockdown is. Just +checking if the class, type and protocol match something is the worse +security verification you can make (or the best, for someone willing +to break it). If you need something secure, use crypto and Certificate +Authentication or stuff like that. Something simple for an storage key +could be: + +function device_is_my_type() +{ + echo 1 > authorized # temporarily authorize it + # FIXME: make sure none can mount it + mount DEVICENODE /mntpoint + sum=$(md5sum /mntpoint/.signature) + if [ $sum = $(cat /etc/lockdown/keysum) ] + then + echo "We are good, connected" + umount /mntpoint + # Other stuff so others can use it + else + echo 0 > authorized + fi +} + + +Of course, this is lame, you'd want to do a real certificate +verification stuff with PKI, so you don't depend on a shared secret, +etc, but you get the idea. Anybody with access to a device gadget kit +can fake descriptors and device info. Don't trust that. You are +welcome. + diff --git a/Documentation/usb/power-management.txt b/Documentation/usb/power-management.txt new file mode 100644 index 00000000000..97842deec47 --- /dev/null +++ b/Documentation/usb/power-management.txt @@ -0,0 +1,517 @@ + Power Management for USB + + Alan Stern <stern@rowland.harvard.edu> + + October 5, 2007 + + + + What is Power Management? + ------------------------- + +Power Management (PM) is the practice of saving energy by suspending +parts of a computer system when they aren't being used. While a +component is "suspended" it is in a nonfunctional low-power state; it +might even be turned off completely. A suspended component can be +"resumed" (returned to a functional full-power state) when the kernel +needs to use it. (There also are forms of PM in which components are +placed in a less functional but still usable state instead of being +suspended; an example would be reducing the CPU's clock rate. This +document will not discuss those other forms.) + +When the parts being suspended include the CPU and most of the rest of +the system, we speak of it as a "system suspend". When a particular +device is turned off while the system as a whole remains running, we +call it a "dynamic suspend" (also known as a "runtime suspend" or +"selective suspend"). This document concentrates mostly on how +dynamic PM is implemented in the USB subsystem, although system PM is +covered to some extent (see Documentation/power/*.txt for more +information about system PM). + +Note: Dynamic PM support for USB is present only if the kernel was +built with CONFIG_USB_SUSPEND enabled. System PM support is present +only if the kernel was built with CONFIG_SUSPEND or CONFIG_HIBERNATION +enabled. + + + What is Remote Wakeup? + ---------------------- + +When a device has been suspended, it generally doesn't resume until +the computer tells it to. Likewise, if the entire computer has been +suspended, it generally doesn't resume until the user tells it to, say +by pressing a power button or opening the cover. + +However some devices have the capability of resuming by themselves, or +asking the kernel to resume them, or even telling the entire computer +to resume. This capability goes by several names such as "Wake On +LAN"; we will refer to it generically as "remote wakeup". When a +device is enabled for remote wakeup and it is suspended, it may resume +itself (or send a request to be resumed) in response to some external +event. Examples include a suspended keyboard resuming when a key is +pressed, or a suspended USB hub resuming when a device is plugged in. + + + When is a USB device idle? + -------------------------- + +A device is idle whenever the kernel thinks it's not busy doing +anything important and thus is a candidate for being suspended. The +exact definition depends on the device's driver; drivers are allowed +to declare that a device isn't idle even when there's no actual +communication taking place. (For example, a hub isn't considered idle +unless all the devices plugged into that hub are already suspended.) +In addition, a device isn't considered idle so long as a program keeps +its usbfs file open, whether or not any I/O is going on. + +If a USB device has no driver, its usbfs file isn't open, and it isn't +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. + +Of course, nothing the kernel does on its own initiative should +prevent the computer or its devices from working properly. If a +device has been autosuspended and a program tries to use it, the +kernel will automatically resume the device (autoresume). For the +same reason, an autosuspended device will usually have remote wakeup +enabled, if the device supports remote wakeup. + +It is worth mentioning that many USB drivers don't support +autosuspend. In fact, at the time of this writing (Linux 2.6.23) the +only drivers which do support it are the hub driver, kaweth, asix, +usblp, usblcd, and usb-skeleton (which doesn't count). If a +non-supporting driver is bound to a device, the device won't be +autosuspended. In effect, the kernel pretends the device is never +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. + + + The user interface for dynamic PM + --------------------------------- + +The user interface for controlling dynamic PM is located in the power/ +subdirectory of each USB device's sysfs directory, that is, in +/sys/bus/usb/devices/.../power/ where "..." is the device's ID. The +relevant attribute files are: wakeup, level, and autosuspend. + + power/wakeup + + This file is empty if the device does not support + remote wakeup. Otherwise the file contains either the + word "enabled" or the word "disabled", and you can + write those words to the file. The setting determines + whether or not remote wakeup will be enabled when the + device is next suspended. (If the setting is changed + while the device is suspended, the change won't take + effect until the following suspend.) + + power/level + + This file contains one of three words: "on", "auto", + or "suspend". You can write those words to the file + to change the device's setting. + + "on" means that the device should be resumed and + autosuspend is not allowed. (Of course, system + suspends are still allowed.) + + "auto" is the normal state in which the kernel is + allowed to autosuspend and autoresume the device. + + "suspend" means that the device should remain + suspended, and autoresume is not allowed. (But remote + wakeup may still be allowed, since it is controlled + separately by the power/wakeup attribute.) + + power/autosuspend + + This file contains an integer value, which is the + 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. + +Writing "-1" to power/autosuspend and writing "on" to power/level do +essentially the same thing -- they both prevent the device from being +autosuspended. Yes, this is a redundancy in the API. + +(In 2.6.21 writing "0" to power/autosuspend would prevent the device +from being autosuspended; the behavior was changed in 2.6.22. The +power/autosuspend attribute did not exist prior to 2.6.21, and the +power/level attribute did not exist prior to 2.6.22.) + + + Changing the default idle-delay time + ------------------------------------ + +The default autosuspend idle-delay time is controlled by a module +parameter in usbcore. You can specify the value when usbcore is +loaded. For example, to set it to 5 seconds instead of 2 you would +do: + + modprobe usbcore autosuspend=5 + +Equivalently, you could add to /etc/modprobe.conf a line saying: + + options usbcore autosuspend=5 + +Some distributions load the usbcore module very early during the boot +process, by means of a program or script running from an initramfs +image. To alter the parameter value you would have to rebuild that +image. + +If usbcore is compiled into the kernel rather than built as a loadable +module, you can add + + usbcore.autosuspend=5 + +to the kernel's boot command line. + +Finally, the parameter value can be changed while the system is +running. If you do: + + echo 5 >/sys/module/usbcore/parameters/autosuspend + +then each new USB device will have its autosuspend idle-delay +initialized to 5. (The idle-delay values for already existing devices +will not be affected.) + +Setting the initial default idle-delay to -1 will prevent any +autosuspend of any USB device. This is a simple alternative to +disabling CONFIG_USB_SUSPEND and rebuilding the kernel, and it has the +added benefit of allowing you to enable autosuspend for selected +devices. + + + Warnings + -------- + +The USB specification states that all USB devices must support power +management. Nevertheless, the sad fact is that many devices do not +support it very well. You can suspend them all right, but when you +try to resume them they disconnect themselves from the USB bus or +they stop working entirely. This seems to be especially prevalent +among printers and scanners, but plenty of other types of device have +the same deficiency. + +For this reason, by default the kernel disables autosuspend (the +power/level attribute is initialized to "on") for all devices other +than hubs. Hubs, at least, appear to be reasonably well-behaved in +this regard. + +(In 2.6.21 and 2.6.22 this wasn't the case. Autosuspend was enabled +by default for almost all USB devices. A number of people experienced +problems as a result.) + +This means that non-hub devices won't be autosuspended unless the user +or a program explicitly enables it. As of this writing there aren't +any widespread programs which will do this; we hope that in the near +future device managers such as HAL will take on this added +responsibility. In the meantime you can always carry out the +necessary operations by hand or add them to a udev script. You can +also change the idle-delay time; 2 seconds is not the best choice for +every device. + +Sometimes it turns out that even when a device does work okay with +autosuspend there are still problems. For example, there are +experimental patches adding autosuspend support to the usbhid driver, +which manages keyboards and mice, among other things. Tests with a +number of keyboards showed that typing on a suspended keyboard, while +causing the keyboard to do a remote wakeup all right, would +nonetheless frequently result in lost keystrokes. Tests with mice +showed that some of them would issue a remote-wakeup request in +response to button presses but not to motion, and some in response to +neither. + +The kernel will not prevent you from enabling autosuspend on devices +that can't handle it. It is even possible in theory to damage a +device by suspending it at the wrong time -- for example, suspending a +USB hard disk might cause it to spin down without parking the heads. +(Highly unlikely, but possible.) Take care. + + + The driver interface for Power Management + ----------------------------------------- + +The requirements for a USB driver to support external power management +are pretty modest; the driver need only define + + .suspend + .resume + .reset_resume + +methods in its usb_driver structure, and the reset_resume method is +optional. The methods' jobs are quite simple: + + The suspend method is called to warn the driver that the + device is going to be suspended. If the driver returns a + negative error code, the suspend will be aborted. Normally + the driver will return 0, in which case it must cancel all + outstanding URBs (usb_kill_urb()) and not submit any more. + + The resume method is called to tell the driver that the + device has been resumed and the driver can return to normal + operation. URBs may once more be submitted. + + The reset_resume method is called to tell the driver that + the device has been resumed and it also has been reset. + The driver should redo any necessary device initialization, + since the device has probably lost most or all of its state + (although the interfaces will be in the same altsettings as + before the suspend). + +The reset_resume method is used by the USB Persist facility (see +Documentation/usb/persist.txt) and it can also be used under certain +circumstances when CONFIG_USB_PERSIST is not enabled. Currently, if a +device is reset during a resume and the driver does not have a +reset_resume method, the driver won't receive any notification about +the resume. Later kernels will call the driver's disconnect method; +2.6.23 doesn't do this. + +USB drivers are bound to interfaces, so their suspend and resume +methods get called when the interfaces are suspended or resumed. In +principle one might want to suspend some interfaces on a device (i.e., +force the drivers for those interface to stop all activity) without +suspending the other interfaces. The USB core doesn't allow this; all +interfaces are suspended when the device itself is suspended and all +interfaces are resumed when the device is resumed. It isn't possible +to suspend or resume some but not all of a device's interfaces. The +closest you can come is to unbind the interfaces' drivers. + + + The driver interface for autosuspend and autoresume + --------------------------------------------------- + +To support autosuspend and autoresume, a driver should implement all +three of the methods listed above. In addition, a driver indicates +that it supports autosuspend by setting the .supports_autosuspend flag +in its usb_driver structure. It is then responsible for informing the +USB core whenever one of its interfaces becomes busy or idle. The +driver does so by calling these three functions: + + int usb_autopm_get_interface(struct usb_interface *intf); + void usb_autopm_put_interface(struct usb_interface *intf); + int usb_autopm_set_interface(struct usb_interface *intf); + +The functions work by maintaining a counter in the usb_interface +structure. When intf->pm_usage_count is > 0 then the interface is +deemed to be busy, and the kernel will not autosuspend the interface's +device. When intf->pm_usage_count is <= 0 then the interface is +considered to be idle, and the kernel may autosuspend the device. + +(There is a similar pm_usage_count field in struct usb_device, +associated with the device itself rather than any of its interfaces. +This field is used only by the USB core.) + +The driver owns intf->pm_usage_count; it can modify the value however +and whenever it likes. A nice aspect of the usb_autopm_* routines is +that the changes they make are protected by the usb_device structure's +PM mutex (udev->pm_mutex); however drivers may change pm_usage_count +without holding the mutex. + + usb_autopm_get_interface() increments pm_usage_count and + attempts an autoresume if the new value is > 0 and the + device is suspended. + + usb_autopm_put_interface() decrements pm_usage_count and + attempts an autosuspend if the new value is <= 0 and the + device isn't suspended. + + usb_autopm_set_interface() leaves pm_usage_count alone. + It attempts an autoresume if the value is > 0 and the device + is suspended, and it attempts an autosuspend if the value is + <= 0 and the device isn't suspended. + +There also are a couple of utility routines drivers can use: + + usb_autopm_enable() sets pm_usage_cnt to 1 and then calls + usb_autopm_set_interface(), which will attempt an autoresume. + + usb_autopm_disable() sets pm_usage_cnt to 0 and then calls + usb_autopm_set_interface(), which will attempt an autosuspend. + +The conventional usage pattern is that a driver calls +usb_autopm_get_interface() in its open routine and +usb_autopm_put_interface() in its close or release routine. But +other patterns are possible. + +The autosuspend attempts mentioned above will often fail for one +reason or another. For example, the power/level attribute might be +set to "on", or another interface in the same device might not be +idle. This is perfectly normal. If the reason for failure was that +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. + + + Other parts of the driver interface + ----------------------------------- + +Sometimes a driver needs to make sure that remote wakeup is enabled +during autosuspend. For example, there's not much point +autosuspending a keyboard if the user can't cause the keyboard to do a +remote wakeup by typing on it. If the driver sets +intf->needs_remote_wakeup to 1, the kernel won't autosuspend the +device if remote wakeup isn't available or has been disabled through +the power/wakeup attribute. (If the device is already autosuspended, +though, setting this flag won't cause the kernel to autoresume it. +Normally a driver would set this flag in its probe method, at which +time the device is guaranteed not to be autosuspended.) + +The usb_autopm_* routines have to run in a sleepable process context; +they must not be called from an interrupt handler or while holding a +spinlock. In fact, the entire autosuspend mechanism is not well geared +toward interrupt-driven operation. However there is one thing a +driver can do in an interrupt handler: + + usb_mark_last_busy(struct usb_device *udev); + +This sets udev->last_busy to the current time. udev->last_busy is the +field used for idle-delay calculations; updating it will cause any +pending autosuspend to be moved back. The usb_autopm_* routines will +also set the last_busy field to the current time. + +Calling urb_mark_last_busy() from within an URB completion handler is +subject to races: The kernel may have just finished deciding the +device has been idle for long enough but not yet gotten around to +calling the driver's suspend method. The driver would have to be +responsible for synchronizing its suspend method with its URB +completion handler and causing the autosuspend to fail with -EBUSY if +an URB had completed too recently. + +External suspend calls should never be allowed to fail in this way, +only autosuspend calls. The driver can tell them apart by checking +udev->auto_pm; this flag will be set to 1 for internal PM events +(autosuspend or autoresume) and 0 for external PM events. + +Many of the ingredients in the autosuspend framework are oriented +towards interfaces: The usb_interface structure contains the +pm_usage_cnt field, and the usb_autopm_* routines take an interface +pointer as their argument. But somewhat confusingly, a few of the +pieces (usb_mark_last_busy() and udev->auto_pm) use the usb_device +structure instead. Drivers need to keep this straight; they can call +interface_to_usbdev() to find the device structure for a given +interface. + + + Locking requirements + -------------------- + +All three suspend/resume methods are always called while holding the +usb_device's PM mutex. For external events -- but not necessarily for +autosuspend or autoresume -- the device semaphore (udev->dev.sem) will +also be held. This implies that external suspend/resume events are +mutually exclusive with calls to probe, disconnect, pre_reset, and +post_reset; the USB core guarantees that this is true of internal +suspend/resume events as well. + +If a driver wants to block all suspend/resume calls during some +critical section, it can simply acquire udev->pm_mutex. +Alternatively, if the critical section might call some of the +usb_autopm_* routines, the driver can avoid deadlock by doing: + + down(&udev->dev.sem); + rc = usb_autopm_get_interface(intf); + +and at the end of the critical section: + + if (!rc) + usb_autopm_put_interface(intf); + up(&udev->dev.sem); + +Holding the device semaphore will block all external PM calls, and the +usb_autopm_get_interface() will prevent any internal PM calls, even if +it fails. (Exercise: Why?) + +The rules for locking order are: + + Never acquire any device semaphore while holding any PM mutex. + + Never acquire udev->pm_mutex while holding the PM mutex for + a device that isn't a descendant of udev. + +In other words, PM mutexes should only be acquired going up the device +tree, and they should be acquired only after locking all the device +semaphores you need to hold. These rules don't matter to drivers very +much; they usually affect just the USB core. + +Still, drivers do need to be careful. For example, many drivers use a +private mutex to synchronize their normal I/O activities with their +disconnect method. Now if the driver supports autosuspend then it +must call usb_autopm_put_interface() from somewhere -- maybe from its +close method. It should make the call while holding the private mutex, +since a driver shouldn't call any of the usb_autopm_* functions for an +interface from which it has been unbound. + +But the usb_autpm_* routines always acquire the device's PM mutex, and +consequently the locking order has to be: private mutex first, PM +mutex second. Since the suspend method is always called with the PM +mutex held, it mustn't try to acquire the private mutex. It has to +synchronize with the driver's I/O activities in some other way. + + + Interaction between dynamic PM and system PM + -------------------------------------------- + +Dynamic power management and system power management can interact in +a couple of ways. + +Firstly, a device may already be manually suspended or autosuspended +when a system suspend occurs. Since system suspends are supposed to +be as transparent as possible, the device should remain suspended +following the system resume. The 2.6.23 kernel obeys this principle +for manually suspended devices but not for autosuspended devices; they +do get resumed when the system wakes up. (Presumably they will be +autosuspended again after their idle-delay time expires.) In later +kernels this behavior will be fixed. + +(There is an exception. If a device would undergo a reset-resume +instead of a normal resume, and the device is enabled for remote +wakeup, then the reset-resume takes place even if the device was +already suspended when the system suspend began. The justification is +that a reset-resume is a kind of remote-wakeup event. Or to put it +another way, a device which needs a reset won't be able to generate +normal remote-wakeup signals, so it ought to be resumed immediately.) + +Secondly, a dynamic power-management event may occur as a system +suspend is underway. The window for this is short, since system +suspends don't take long (a few seconds usually), but it can happen. +For example, a suspended device may send a remote-wakeup signal while +the system is suspending. The remote wakeup may succeed, which would +cause the system suspend to abort. If the remote wakeup doesn't +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. diff --git a/Documentation/usb/usb-serial.txt b/Documentation/usb/usb-serial.txt index 5b635ae8494..4e0b62b8566 100644 --- a/Documentation/usb/usb-serial.txt +++ b/Documentation/usb/usb-serial.txt @@ -428,6 +428,17 @@ Options supported: See http://www.uuhaus.de/linux/palmconnect.html for up-to-date information on this driver. +Winchiphead CH341 Driver + + This driver is for the Winchiphead CH341 USB-RS232 Converter. This chip + also implements an IEEE 1284 parallel port, I2C and SPI, but that is not + supported by the driver. The protocol was analyzed from the behaviour + of the Windows driver, no datasheet is available at present. + The manufacturer's website: http://www.winchiphead.com/. + For any questions or problems with this driver, please contact + frank@kingswood-consulting.co.uk. + + Generic Serial driver If your device is not one of the above listed devices, compatible with diff --git a/Documentation/usb/usbmon.txt b/Documentation/usb/usbmon.txt index 53ae866ae37..2917ce4ffdc 100644 --- a/Documentation/usb/usbmon.txt +++ b/Documentation/usb/usbmon.txt @@ -34,9 +34,12 @@ if usbmon is built into the kernel. Verify that bus sockets are present. # ls /sys/kernel/debug/usbmon -1s 1t 1u 2s 2t 2u 3s 3t 3u 4s 4t 4u +0s 0t 0u 1s 1t 1u 2s 2t 2u 3s 3t 3u 4s 4t 4u # +Now you can choose to either use the sockets numbered '0' (to capture packets on +all buses), and skip to step #3, or find the bus used by your device with step #2. + 2. Find which bus connects to the desired device Run "cat /proc/bus/usb/devices", and find the T-line which corresponds to @@ -56,6 +59,10 @@ Bus=03 means it's bus 3. # cat /sys/kernel/debug/usbmon/3u > /tmp/1.mon.out +to listen on a single bus, otherwise, to listen on all buses, type: + +# cat /sys/kernel/debug/usbmon/0u > /tmp/1.mon.out + This process will be reading until killed. Naturally, the output can be redirected to a desirable location. This is preferred, because it is going to be quite long. |