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    SubjectRe: [PATCH 5/5] CUSE: implement CUSE - Character device in Userspace
    On Thu, 28 Aug 2008 15:15:25 -0700
    Greg KH <greg@kroah.com> wrote:

    > On Thu, Aug 28, 2008 at 01:07:40PM -0700, Andrew Morton wrote:
    > > On Fri, 29 Aug 2008 03:19:04 +0900
    > > Tejun Heo <tj@kernel.org> wrote:
    > > > +#define fc_to_cc(_fc) container_of((_fc), struct cuse_conn, fc)
    > > > +#define cdev_to_cc(_cdev) container_of((_cdev), struct cuse_conn, cdev)
    > > > +#define cuse_conn_get(cc) ({mntget((cc)->mnt); cc;})
    > > > +#define cuse_conn_put(cc) mntput((cc)->mnt)
    > >
    > > I believe all the above could be implemented in C.
    >
    > "traditionally" container_of() is used in #define, not a function call
    > as it is just pointer math that can be done at compile time.
    >

    Well yeah. But it isn't a very good tradition.

    static inline struct cuse_conn *cdev_to_cc(struct cdev *cdev)
    {
    return container_of(cdev, struct cuse_conn, cdev);
    }

    should generate the same code and is prettier.

    Unfortunately it has no additional type-safety. You can still pass it
    the address of a tty_driver.cdev instead of a cuse_conn.cdev and the
    compiler will happily swallow it. Not a big problem in practice though.



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