83cb2604f6
Expose usb device state to userland as the information is useful in detecting non-compliant setups and diagnosing enumeration failures. For example: - End-to-end signal integrity issues: the device would fail port reset repeatedly and thus be stuck in POWERED state. - Charge-only cables (missing D+/D- lines): the device would never enter POWERED state as the HC would not see any pullup. What's the status quo? We do have error logs such as "Cannot enable. Maybe the USB cable is bad?" to flag potential setup issues, but there's no good way to expose them to userspace. Why add a sysfs entry in struct usb_port instead of struct usb_device? The struct usb_device is not device_add() to the system until it's in ADDRESS state hence we would miss the first two states. The struct usb_port is a better place to keep the information because its life cycle is longer than the struct usb_device that is attached to the port. Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202306042228.e532af6e-oliver.sang@intel.com Reviewed-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Roy Luo <royluo@google.com> Message-ID: <20230608015913.1679984-1-royluo@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.