sound: make OSS device number claiming optional and schedule its removal
If any OSS support is enabled, regardless of built-in or module, sound_core claims full OSS major number (that is, the old 0-255 region) to trap open attempts and request sound modules using custom module aliases. This feature is redundant as chrdev already has such mechanism. This preemptive claiming prevents alternative OSS implementation. The custom module aliases are scheduled to be removed and the previous patch made soundcore emit the standard chrdev aliases too to help transition. This patch schedule the feature for removal in a year and makes it optional so that developers and distros can try new things in the meantime without rebuilding the kernel. The pre-claiming can be turned off by using SOUND_OSS_CORE_PRECLAIM and/or kernel parameter soundcore.preclaim_oss. As this allows sound minors to be individually grabbed by other users, this patch updates sound_insert_unit() such that if registering individual device region fails, it tries the next available slot. For details on removal plan, please read the entry added by this patch in feature-removal-schedule.txt . Signed-off-by: NTejun Heo <tj@kernel.org> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: NTakashi Iwai <tiwai@suse.de>
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