From mboxrd@z Thu Jan  1 00:00:00 1970
From: peterghamilton@gmail.com (Peter Hamilton)
Date: Thu, 26 May 2011 14:46:08 -0600
Subject: Struct Inheritance in drivers/ata/
Message-ID: <BANLkTimjsJEZKqzX=btryBoXD0FNAsW8Ag@mail.gmail.com>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

The code in drivers/ata/ uses an implementation of inheritance that I have
not seen before.  It's only briefly explained in the header file (
include/linux/libata.h:885):

/*
 * ->inherits must be the last field and all the preceding
 * fields must be pointers.
 */

The structs are then initialized with .inherits assigned first:

drivers/ata/sata_nv.c:475

static struct ata_port_operations nv_nf2_ops = {

        .inherits               = &nv_generic_ops,
        .freeze                 = nv_nf2_freeze,

        .thaw                   = nv_nf2_thaw,

};


Is this actually implementing inheritance?  Why do all preceding fields need
to be pointers?

As far as I can tell, this style is only found in the ata drivers.

Could anyone explain how this works?

Thanks,
Peter
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