407359d44e
In command DSP models, one meter information consists of 4 bytes for IEEE 764 floating point (binary32). In previous patch, it is exported to userspace as 32 bit storage since the storage is also handled in ALSA firewire-motu driver as well in kernel space in which floating point arithmetic is not preferable. On the other hand, ALSA firewire-motu driver doesn't perform floating point calculation. The driver just gather meter information from isochronous packets and fill structure fields for userspace. In 'header' target of Kbuild, UAPI headers are processed before installed. In this timing, #ifdef macro with __KERNEL__ is removed. This mechanism is useful in the case so that the 32 bit storage can be accessible as u32 type in kernel space and float type in user space. We can see the same usage in ''struct acct_v3' in 'include/uapi/linux/acct.h'. This commit is for the above idea. Additionally, due to message protocol, meter information is filled with 0xffffffff in the end of period but 0xffffffff is invalid as binary32. To avoid confusion in userspace application, the last two elements are left without any assignment. Suggested-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> Link: https://lore.kernel.org/r/20211027125529.54295-4-o-takashi@sakamocchi.jp Signed-off-by: Takashi Iwai <tiwai@suse.de>
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.