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Most sysfs attributes are statically defined, the goal with this design being to be able to move all the filesystem description into read-only memory. Anyway, it may be relevant in some cases to populate attributes at run time. This leads to situation where an attribute may or may not be present depending on conditions which are not known at compile time, up to the point where no attribute at all gets added in a folder which then becomes "sometimes" empty. Problem is, providing an attribute group with a name and without .[bin_]attrs members will be loudly refused by the core, leading in most cases to a device registration failure. The simple way to support such situation right now is to dynamically allocate an empty attribute array, which is: * a (small) waste of space * a waste of time * disturbing, to say the least, as an empty sysfs folder will be created anyway. Another (even worse) possibility would be to dynamically overwrite a member of the attribute_group list, hopefully the last, which is also supposed to remain in the read-only section. In order to avoid these hackish situations, while still giving a little bit of flexibility, we might just check the validity of the .[bin_]attrs list and, if empty, just skip the attribute group creation instead of failing. This way, developers will not be tempted to workaround the core with useless allocations or strange writes on supposedly read-only structures. The content of the WARN() message is kept but turned into a debug message in order to help developers understanding why their sysfs folders might now silently fail to be created. Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Message-ID: <20230614063018.2419043-3-miquel.raynal@bootlin.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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| 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.