MOD_INC_USE_COUNT, MOD_DEC_USE_COUNT - Support reference
counting of modules
These macros support reference counting of modules during
their lifetime. Each time MOD_INC_USE_COUNT(9) is invoked,
the kernel increases the number of counted references to the
module. The MOD_DEC_USE_COUNT(9) decreases the reference
The reference count is used by the kernel to know when a
module is no longer in use by the device or application
software. A MOD_INC_USE_COUNT(9) is generally placed in the
open entry for a driver, and a MOD_DEC_USE_COUNT(9) in the
release for the driver, to count the number of times the
device has been opened, and thus prevent the module being
unloaded when in use. The device driver may increment the
use count other times, such as when memory is mapped or the
module must remain loaded for external events.
If the device driver is not compiled as a module is not
defined) then the macro reduces to no behavior.
These macros take no parameters and return no result.
Stephen Williams <email@example.com>