Hi,
I've been looking through some of the device drivers and find quite often a call
to request_region of the form:
if (!request_region(IO_INDEX_PORT, 2, WATCHDOG_NAME))
{
printk(KERN_ERR PFX "I/O address 0x%04x already in use\n",
IO_INDEX_PORT);
rc = -EIO;
goto err_out;
}
I was interested in finding out what happens to the pointer which is returned
from request_region. This if statement simply interests itself with the case of
request_region returning NULL and makes no consideration that a pointer may be
returned.
The request_region is a macro which maps onto __request_region. In this
function, a pointer to struct resource is allocated memory via kzalloc. This is
done right at the begining of the __request_region function. The function
__request_region itself calls the function __request_resource and on this
returning a NULL value, then the pointer to the memory allocated via kzalloc is
returned.
So, if the above if statement is != NULL, then who looks after freeing up the
pointer which was returned?
I must be missing something, as calls of this form are done a lot in drivers.
Cheers, Mark.
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