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Benjamin Tissoires 8a89db5187 HID: bpf: Add a HID report composition helper macros
These macros make it slightly easier and more modular to create
a HID report descriptor from scratch. Since they carry the annotation
we don't need to comment it and they cannot get stale.

For comparison, before we had this:

        0x15, 0x00,                    //   Logical Minimum (0)
        0x25, 0x01,                    //   Logical Maximum (1)
        0x95, 0x04,                    //   Report Count (4)
        0x75, 0x01,                    //   Report Size (1)

Now we can write this as:
        LogicalRange_i8(0, 1)
        ReportCount(4)
        ReportSize(1)

Because these macros are for creating new report descriptors,
some bits aren't directly exposed. e.g in the example above:
there is a logical range as one macro that sets both min and max.
There is seldom a good use case for skipping either anyway.

These macros will need to be expanded over time.

For Usage Pages and Usage IDs, we use a tool to parse the HUT JSON
(attached to the HUT 1.5 PDF [1]) and generate all #defines for all
usage pages and usages in the form:

 #define UsagePage_Foo_Bar
 #define Usage_FB_SomeOrOther

Where the FB is simply the acronym based on the capital letters in the
Usage Page name or the first three letters, whichever makes slightly
more sense.

[1] https://usb.org/document-library/hid-usage-tables-15

Link: https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/92
Link: https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/96
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Link: https://patch.msgid.link/20240627-import-bpf-v1-1-0dbcda4a5b1f@kernel.org
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
History 2024-07-01 14:48:18 +02:00
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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 reStructuredText 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.