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snd_ctl_add_vmaster_hook(9) [centos man page]

SND_CTL_ADD_VMASTER_(9) 					 Control/Mixer API					   SND_CTL_ADD_VMASTER_(9)

NAME
snd_ctl_add_vmaster_hook - Add a hook to a vmaster control SYNOPSIS
int snd_ctl_add_vmaster_hook(struct snd_kcontrol * kcontrol, void (*hook) (void *private_data, int), void * private_data); ARGUMENTS
kcontrol vmaster kctl element hook the hook function private_data the private_data pointer to be saved DESCRIPTION
Adds the given hook to the vmaster control element so that it's called at each time when the value is changed. RETURN
Zero. COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 SND_CTL_ADD_VMASTER_(9)

Check Out this Related Man Page

SHUTDOWNHOOK_ESTABLISH(9)				   BSD Kernel Developer's Manual				 SHUTDOWNHOOK_ESTABLISH(9)

NAME
shutdownhook_establish, shutdownhook_disestablish -- add or remove a shutdown hook SYNOPSIS
void * shutdownhook_establish(void (*fn)(void *), void *arg); void shutdownhook_disestablish(void *cookie); DESCRIPTION
The shutdownhook_establish API is deprecated. The shutdownhook_establish() function adds fn to the list of hooks invoked by doshutdownhooks(9) at shutdown. When invoked, the hook func- tion fn will be passed arg as its only argument. The shutdownhook_disestablish() function removes the hook described by the opaque pointer cookie from the list of hooks to be invoked at shutdown. If cookie is invalid, the result of shutdownhook_disestablish() is undefined. Shutdown hooks should be used to perform one-time activities that must happen immediately before the kernel exits. Because of the environ- ment in which they are run, shutdown hooks cannot rely on many system services (including file systems, and timeouts and other interrupt- driven services), or even basic system integrity (because the system could be rebooting after a crash). RETURN VALUES
If successful, shutdownhook_establish() returns an opaque pointer describing the newly-established shutdown hook. Otherwise, it returns NULL. EXAMPLES
It may be appropriate to use a shutdown hook to disable a device that does direct memory access, so that the device will not try to access memory while the system is rebooting. It may be appropriate to use a shutdown hook to inform watchdog timer hardware that the operating system is no longer running. SEE ALSO
doshutdownhooks(9) BUGS
The names are clumsy, at best. BSD
May 14, 2009 BSD

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