d716742243
Units of TASCAM FireWire series transfer image of states of the unit in tx isochronous packets. Demultiplexing of the states from the packets is done in software interrupt context regardless of any process context. In a view of userspace applications, it needs to have notification mechanism to catch change of the states. This commit implements a queue to store events for the notification. The image of states includes fluctuating data such as level of gain/volume for physical input/output and position of knobs. Therefore the events are queued corresponding to some control features only. Furthermore, the queued events are planned to be consumed by userspace applications via ALSA hwdep interface. This commit suppresses event queueing when no applications open the hwdep interface. However, the queue is maintained in an optimistic scenario, thus without any care against overrrun. This is reasonable because target events are useless just to handle PCM frames. It starts queueing when an usespace application opens hwdep interface, thus it's expected to read the queued events steadily. Signed-off-by: Takashi Sakamoto <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.