In ``<linux/usb/ch9.h>`` you will find the USB data types defined in
chapter 9 of the USB specification. These data types are used throughout
-USB, and in APIs including this host side API, gadget APIs, and usbfs.
+USB, and in APIs including this host side API, gadget APIs, usb character
+devices and debugfs interfaces.
.. kernel-doc:: include/linux/usb/ch9.h
:internal:
.. kernel-doc:: drivers/usb/core/buffer.c
:internal:
-The USB Filesystem (usbfs)
-==========================
+The USB character device nodes
+==============================
-This chapter presents the Linux *usbfs*. You may prefer to avoid writing
-new kernel code for your USB driver; that's the problem that usbfs set
-out to solve. User mode device drivers are usually packaged as
-applications or libraries, and may use usbfs through some programming
-library that wraps it. Such libraries include
+This chapter presents the Linux character device nodes. You may prefer
+to avoid writing new kernel code for your USB driver. User mode device
+drivers are usually packaged as applications or libraries, and may use
+character devices through some programming library that wraps it.
+Such libraries include
`libusb <http://libusb.sourceforge.net>`__ for C/C++, and
`jUSB <http://jUSB.sourceforge.net>`__ for Java.
.. note::
- This particular documentation is incomplete, especially with respect
- to the asynchronous mode. As of kernel 2.5.66 the code and this
- (new) documentation need to be cross-reviewed.
+ - They were used to be implemented via *usbfs*, but this is not part of
+ the sysfs debug interface.
-Configure usbfs into Linux kernels by enabling the *USB filesystem*
-option (CONFIG_USB_DEVICEFS), and you get basic support for user mode
-USB device drivers. Until relatively recently it was often (confusingly)
-called *usbdevfs* although it wasn't solving what *devfs* was. Every USB
-device will appear in usbfs, regardless of whether or not it has a
-kernel driver.
+ - This particular documentation is incomplete, especially with respect
+ to the asynchronous mode. As of kernel 2.5.66 the code and this
+ (new) documentation need to be cross-reviewed.
-What files are in "usbfs"?
---------------------------
+What files are in "devtmpfs"?
+-----------------------------
-Conventionally mounted at ``/proc/bus/usb``, usbfs features include:
+Conventionally mounted at ``/dev/bus/usb/``, usbfs features include:
-- ``/proc/bus/usb/devices`` ... a text file showing each of the USB
- devices on known to the kernel, and their configuration descriptors.
- You can also poll() this to learn about new devices.
-
-- ``/proc/bus/usb/BBB/DDD`` ... magic files exposing the each device's
+- ``/dev/bus/usb//BBB/DDD`` ... magic files exposing the each device's
configuration descriptors, and supporting a series of ioctls for
making device requests, including I/O to devices. (Purely for access
by programs.)
example you can be sure that you told the right UPS to power down its
second server. "usbfs" doesn't (yet) expose those IDs.
-Mounting and Access Control
----------------------------
-
-There are a number of mount options for usbfs, which will be of most
-interest to you if you need to override the default access control
-policy. That policy is that only root may read or write device files
-(``/proc/bus/BBB/DDD``) although anyone may read the ``devices`` or
-``drivers`` files. I/O requests to the device also need the
-CAP_SYS_RAWIO capability,
-
-The significance of that is that by default, all user mode device
-drivers need super-user privileges. You can change modes or ownership in
-a driver setup when the device hotplugs, or maye just start the driver
-right then, as a privileged server (or some activity within one). That's
-the most secure approach for multi-user systems, but for single user
-systems ("trusted" by that user) it's more convenient just to grant
-everyone all access (using the *devmode=0666* option) so the driver can
-start whenever it's needed.
-
-The mount options for usbfs, usable in /etc/fstab or in command line
-invocations of *mount*, are:
-
-*busgid*\ =NNNNN
- Controls the GID used for the /proc/bus/usb/BBB directories.
- (Default: 0)
-
-*busmode*\ =MMM
- Controls the file mode used for the /proc/bus/usb/BBB directories.
- (Default: 0555)
-
-*busuid*\ =NNNNN
- Controls the UID used for the /proc/bus/usb/BBB directories.
- (Default: 0)
-
-*devgid*\ =NNNNN
- Controls the GID used for the /proc/bus/usb/BBB/DDD files. (Default:
- 0)
-
-*devmode*\ =MMM
- Controls the file mode used for the /proc/bus/usb/BBB/DDD files.
- (Default: 0644)
-
-*devuid*\ =NNNNN
- Controls the UID used for the /proc/bus/usb/BBB/DDD files. (Default:
- 0)
-
-*listgid*\ =NNNNN
- Controls the GID used for the /proc/bus/usb/devices and drivers
- files. (Default: 0)
-
-*listmode*\ =MMM
- Controls the file mode used for the /proc/bus/usb/devices and
- drivers files. (Default: 0444)
-
-*listuid*\ =NNNNN
- Controls the UID used for the /proc/bus/usb/devices and drivers
- files. (Default: 0)
-
-Note that many Linux distributions hard-wire the mount options for usbfs
-in their init scripts, such as ``/etc/rc.d/rc.sysinit``, rather than
-making it easy to set this per-system policy in ``/etc/fstab``.
-
-/proc/bus/usb/devices
----------------------
-
-This file is handy for status viewing tools in user mode, which can scan
-the text format and ignore most of it. More detailed device status
-(including class and vendor status) is available from device-specific
-files. For information about the current format of this file, see the
-``Documentation/usb/proc_usb_info.txt`` file in your Linux kernel
-sources.
-
-This file, in combination with the poll() system call, can also be used
-to detect when devices are added or removed::
-
- int fd;
- struct pollfd pfd;
-
- fd = open("/proc/bus/usb/devices", O_RDONLY);
- pfd = { fd, POLLIN, 0 };
- for (;;) {
- /* The first time through, this call will return immediately. */
- poll(&pfd, 1, -1);
-
- /* To see what's changed, compare the file's previous and current
- contents or scan the filesystem. (Scanning is more precise.) */
- }
-
-Note that this behavior is intended to be used for informational and
-debug purposes. It would be more appropriate to use programs such as
-udev or HAL to initialize a device or start a user-mode helper program,
-for instance.
-
-/proc/bus/usb/BBB/DDD
+/dev/bus/usb//BBB/DDD
---------------------
Use these files in one of these basic ways:
Such a driver first needs to find a device file for a device it knows
how to handle. Maybe it was told about it because a ``/sbin/hotplug``
event handling agent chose that driver to handle the new device. Or
-maybe it's an application that scans all the /proc/bus/usb device files,
+maybe it's an application that scans all the /dev/bus/usb/ device files,
and ignores most devices. In either case, it should :c:func:`read()`
all the descriptors from the device file, and check them against what it
knows how to handle. It might just reject everything except a particular
USBDEVFS_SUBMITURB
*TBS*
+
+The USB devices
+===============
+
+The USB devices are now exported via debugfs:
+
+- ``/sys/kernel/debug/usb/devices`` ... a text file showing each of the USB
+ devices on known to the kernel, and their configuration descriptors.
+ You can also poll() this to learn about new devices.
+
+/sys/kernel/debug/usb/devices
+-----------------------------
+
+This file is handy for status viewing tools in user mode, which can scan
+the text format and ignore most of it. More detailed device status
+(including class and vendor status) is available from device-specific
+files. For information about the current format of this file, see the
+``Documentation/usb/proc_usb_info.txt`` file in your Linux kernel
+sources.
+
+This file, in combination with the poll() system call, can also be used
+to detect when devices are added or removed::
+
+ int fd;
+ struct pollfd pfd;
+
+ fd = open("/sys/kernel/debug/usb/devices", O_RDONLY);
+ pfd = { fd, POLLIN, 0 };
+ for (;;) {
+ /* The first time through, this call will return immediately. */
+ poll(&pfd, 1, -1);
+
+ /* To see what's changed, compare the file's previous and current
+ contents or scan the filesystem. (Scanning is more precise.) */
+ }
+
+Note that this behavior is intended to be used for informational and
+debug purposes. It would be more appropriate to use programs such as
+udev or HAL to initialize a device or start a user-mode helper program,
+for instance.
The usbfs filesystem for USB devices is traditionally mounted at
-/proc/bus/usb. It provides the /proc/bus/usb/devices file, as well as
+/proc/bus/usb. It provides the /sys/kernel/debug/usb/devices file, as well as
the /proc/bus/usb/BBB/DDD files.
In many modern systems the usbfs filesystem isn't used at all. Instead
none /proc/bus/usb usbfs defaults 0 0
to /etc/fstab. This will mount usbfs at each reboot.
- You can then issue `cat /proc/bus/usb/devices` to extract
+ You can then issue `cat /sys/kernel/debug/usb/devices` to extract
USB device information, and user mode drivers can use usbfs
to interact with USB devices.
are wTotalLength bytes apart. If a device returns less configuration
descriptor data than indicated by wTotalLength there will be a hole in
the file for the missing bytes. This information is also shown
-in text form by the /proc/bus/usb/devices file, described later.
+in text form by the /sys/kernel/debug/usb/devices file, described later.
These files may also be used to write user-level drivers for the USB
devices. You would open the /proc/bus/usb/BBB/DDD file read/write,
-THE /proc/bus/usb/devices FILE:
+THE /sys/kernel/debug/usb/devices FILE:
-------------------------------
-In /proc/bus/usb/devices, each device's output has multiple
+In /sys/kernel/debug/usb/devices, each device's output has multiple
lines of ASCII output.
I made it ASCII instead of binary on purpose, so that someone
can obtain some useful data from it without the use of an
=======================================================================
-/proc/bus/usb/devices output format:
+/sys/kernel/debug/usb/devices output format:
Legend:
d = decimal number (may have leading spaces or 0's)
If a user or script is interested only in Topology info, for
-example, use something like "grep ^T: /proc/bus/usb/devices"
+example, use something like "grep ^T: /sys/kernel/debug/usb/devices"
for only the Topology lines. A command like
-"grep -i ^[tdp]: /proc/bus/usb/devices" can be used to list
+"grep -i ^[tdp]: /sys/kernel/debug/usb/devices" can be used to list
only the lines that begin with the characters in square brackets,
where the valid characters are TDPCIE. With a slightly more able
script, it can display any selected lines (for example, only T, D,
and P lines) and change their output format. (The "procusb"
Perl script is the beginning of this idea. It will list only
selected lines [selected from TBDPSCIE] or "All" lines from
-/proc/bus/usb/devices.)
+/sys/kernel/debug/usb/devices.)
The Topology lines can be used to generate a graphic/pictorial
of the USB devices on a system's root hub. (See more below
The Configuration lines could be used to list maximum power
(in milliamps) that a system's USB devices are using.
-For example, "grep ^C: /proc/bus/usb/devices".
+For example, "grep ^C: /sys/kernel/debug/usb/devices".
Here's an example, from a system which has a UHCI root hub,
projects / GitHub / LineageOS / android_kernel_motorola_exynos9610.git / commitdiff