Can anyone please tell me the purpose of __devexit_p part in driver files ?
I find __devexit_p is normally using with remove functions in the driver code
Example 1:
static struct i2c_driver lsm9ds0_driver = {
.driver = {
.owner = THIS_MODULE,
.name = LSM9DS0_DEV_NAME,
},
.probe = lsm9ds0_probe,
.remove = __devexit_p(lsm9ds0_remove),
.id_table = lsm9ds0_id,
};
Example 2:
static struct spi_driver light_driver = {
.driver = {
.name = "light",
.owner = THIS_MODULE,
},
.probe = light_probe,
.remove = __devexit_p(light_remove),
};
Is there any difference if I removed __devexit_p from above examples?
Will it affect the performance of the driver when __devexit_p removed?
Based on this LXR listing from 2.6.32:
/*
Functions marked as __devexit may be discarded at kernel link time,
depending on config options. Newer versions of binutils detect references
from retained sections to discarded sections and flag an error. Pointers to
__devexit functions must use __devexit_p(function_name), the wrapper will
insert either the function_name or NULL, depending on the config options.
*/
#if defined(MODULE) || defined(CONFIG_HOTPLUG)
#define __devexit_p(x) x
#else
#define __devexit_p(x) NULL
#endif
it seems to be used to conditionally expand it to the given parameter or NULL based on the code being compiled as part of a kernel module (MODULE) and on the CONFIG_HOTPLUG kernel option.