Re: [PATCH 02/10] sdhci: Add support for bus-specific IO memory accessors

[Arnd Bergmann <arnd@arndb.de>]

On Thursday 22 January 2009, Anton Vorontsov wrote:
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0/*
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * These accessors duplicate s=
dhci_ops, but there are two reasons for
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * this:
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * 1. sdhci_ops are const, so =
the sdhci driver won't able to assign
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * =C2=A0 =C2=A0default ops;

You could assign the pointer to a const default_sdhci_ops structure,
which IMHO would be cleaner than copying the function pointers
separately.

> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * 2. Using host->X instead of=
 host->ops->X saves us one dereference.
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * =C2=A0 =C2=A0This can be us=
eful in PIO mode. (Though the benefit of this
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * =C2=A0 =C2=A0is negligibly =
small).
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */

I doubt that this is even measurable. If it was, you could still use a copy
of that structure, like

struct sdhci_host {
	...
	struct sdhci_ops ops; /* not struct sdhci_ops *ops */
	...
};

and do an assignment of the structure, like

static void assign_ops(struct sdhci_host *host, struct sdhci_ops *ops)
{
	host->ops =3D *ops;
}

	Arnd <><