e8ad415b7a
As a second step for preliminary to widen the devres usages among sound drivers, this patch adds a new ALSA core API function, snd_devm_card_new(), to create a snd_card object via devres. When a card object is created by this new function, snd_card_free() is called automatically and the card object resource gets released at the device unbinding time. However, the story isn't that simple. A caveat is that we have to call snd_card_free() at the very first of the whole resource release procedure, in order to assure that the all exposed devices on user-space are deleted and sync with processes accessing those devices before releasing resources. For achieving it, snd_card_register() adds a new devres action to trigger snd_card_free() automatically when the given card object is a "managed" one. Since usually snd_card_register() is the last step of the initialization, this should work in most cases. With all these tricks, some drivers can get rid of the whole driver remove callback code. About a bit of implementation details: the patch adds two new flags to snd_card object: managed and releasing. The former indicates that the object was created via snd_devm_card_new(), and the latter is used for avoiding the double-free of snd_card_free() calls. Both flags are fairly internal and likely uninteresting to normal users. Link: https://lore.kernel.org/r/20210715075941.23332-3-tiwai@suse.de 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.