Re: [PATCH 3/4] AHCI: Conserve interrupts withpci_enable_msi_block_part() interface

[Tejun Heo]

On Mon, Sep 02, 2013 at 11:00:28AM +0200, Alexander Gordeev wrote:
> +	if (hpriv->flags & AHCI_HFLAG_NO_MSI)
> +		goto intx;
> +
> +	rc = pci_enable_msi_block_part(pdev, n_ports, AHCI_MAX_PORTS);
> +	if (!rc)
> +		return AHCI_MAX_PORTS;
> +	if (rc < 0)
> +		goto intx;
> +
> +	maxvec = rc;
> +	rc = pci_enable_msi_block_part(pdev, n_ports, maxvec);
> +	if (!rc)
> +		return maxvec;
> +	if (rc < 0)
> +		goto intx;

Why is the above fallback necessary?  The only other number which
makes sense is roundup_pow_of_two(n_ports), right?  What does the
above fallback logic buy us?

Thanks.

-- 
tejun
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