On Thu, Jan 22, 2009 at 12:55:48PM +0100, Arnd Bergmann wrote:
> On Thursday 22 January 2009, Anton Vorontsov wrote:
> > + /*
> > + * These accessors duplicate sdhci_ops, but there are two reasons
> > for
> > + * this:
> > + * 1. sdhci_ops are const, so the sdhci driver won't able to assign
> > + * default ops;
>
> You could assign the pointer to a const default_sdhci_ops structure,
> which IMHO would be cleaner than copying the function pointers
> separately.
This won't work because ops also specify non-memory accessors ops
(i.e. enable_dma, set_clock, ...), so we can't just assign
default_ops ptr.
> > + * 2. Using host->X instead of host->ops->X saves us one
> > dereference.
> > + * This can be useful in PIO mode. (Though the benefit of this
> > + * is negligibly small).
> > + */
>
> I doubt that this is even measurable.
Yeah, I didn't even bother w/ measuring. ;-)
> 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 = *ops;
> }
This will work. Pierre, what do you think? That way drivers
will call this routine instead of "host->ops = driver_ops_ptr".
The other option would be to remove const from the ops. Or implement
another non-const ops struct (struct sdhci_io_ops?).
In any way, the type-checked variant will be even longer to type:
host->mem_ops->writel(val, host->ioaddr + reg);
host->ops.writel(val, host->ioaddr + reg);
host->writel(val, host->ioaddr + reg);
Thanks,
--
Anton Vorontsov
email: cbouatmai...@gmail.com
irc://irc.freenode.net/bd2
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