Re: [PATCH 1/4] pci: Update pci_set_vga_state to call arch functions

[Mike Travis]

Andrew Morton wrote:
> On Mon, 18 Jan 2010 12:34:13 -0600
> Mike Travis <travis@xxxxxxx> wrote:
>
> > Update pci_set_vga_state to call arch dependent functions to enable
> > Legacy VGA I/O transactions to be redirected to correct target.
>
> Changelog doesn't explain the reason for doing this, but it looks like
> that becomes clearer in later patches.

You're right, I should have carried more from the intro page into the
actual patch.
> >  
> > +/* Some architectures require additional programming to enable VGA */
> > +static arch_set_vga_state_t arch_set_vga_state;
> > +
> > +void pci_register_set_vga_state(arch_set_vga_state_t func)
> > +{
> > +	arch_set_vga_state = func;	/* NULL disables */
> > +}
> > +
> > +static int pci_set_vga_state_arch(struct pci_dev *dev, bool decode,
> > +		      unsigned int command_bits, bool change_bridge)
> > +{
> > +	if (arch_set_vga_state)
> > +		return arch_set_vga_state(dev, decode, command_bits,
> > +						change_bridge);
> > +	return 0;
> > +}
>
> hm, that's not terribly elegant.  It's racy too, although it seems
> unlikely that an arch will call pci_set_vga_state_arch() more than
> once.

Yes, it's only set (once) if it is a UV system.

> Still, a neater solution might be
>
> int arch_pci_set_vga_state(...) __weak
> {
> 	return 0;
> }
>
> and then resolve it at linkage time?

Wouldn't the linked in stronger function then need to surround
the UV register updating with "if (uv_system)"?

Thanks for the comments Andrew.
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