Re: [PATCH v2 05/14] net: core: provide priv_to_netdev()

[Bartosz Golaszewski]

pon., 11 maj 2020 o 22:41 David Miller <davem@xxxxxxxxxxxxx> napisaÅ(a):
>
> From: Bartosz Golaszewski <brgl@xxxxxxxx>
> Date: Mon, 11 May 2020 17:07:50 +0200
>
> > From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> >
> > Appropriate amount of extra memory for private data is allocated at
> > the end of struct net_device. We have a helper - netdev_priv() - that
> > returns its address but we don't have the reverse: a function which
> > given the address of the private data, returns the address of struct
> > net_device.
> >
> > This has caused many drivers to store the pointer to net_device in
> > the private data structure, which basically means storing the pointer
> > to a structure in this very structure.
> >
> > This patch proposes to add priv_to_netdev() - a helper which converts
> > the address of the private data to the address of the associated
> > net_device.
> >
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
>
> Sorry, please don't do this.  We had this almost two decades ago and
> explicitly removed it intentionally.
>
> Store the back pointer in your software state just like everyone else
> does.

I will if you insist but would you mind sharing some details on why it
was removed? To me it still makes more sense than storing the pointer
to a structure in *that* structure.

Bart