netdev - Re: [PATCH RFC 00/77] Re-design MSI/MSI-X interrupts enablement pattern

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Date:	Tue, 08 Oct 2013 20:55:03 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Alexander Gordeev <agordeev@...hat.com>
CC:	linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Michael Ellerman <michael@...erman.id.au>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
	Dan Williams <dan.j.williams@...el.com>,
	Andy King <acking@...are.com>, Jon Mason <jon.mason@...el.com>,
	Matt Porter <mporter@...nel.crashing.org>,
	linux-pci@...r.kernel.org, linux-mips@...ux-mips.org,
	linuxppc-dev@...ts.ozlabs.org, linux390@...ibm.com,
	linux-s390@...r.kernel.org, x86@...nel.org,
	linux-ide@...r.kernel.org, iss_storagedev@...com,
	linux-nvme@...ts.infradead.org, linux-rdma@...r.kernel.org,
	netdev@...r.kernel.org, e1000-devel@...ts.sourceforge.net,
	linux-driver@...gic.com,
	Solarflare linux maintainers <linux-net-drivers@...arflare.com>,
	VMware@...p-26-207.brq.redhat.com, "Inc." <pv-drivers@...are.com>,
	linux-scsi@...r.kernel.org
Subject: Re: [PATCH RFC 00/77] Re-design MSI/MSI-X interrupts enablement pattern

On 10/02/2013 03:29 AM, Alexander Gordeev wrote:
> 
> As result, device drivers will cease to use the overcomplicated
> repeated fallbacks technique and resort to a straightforward
> pattern - determine the number of MSI/MSI-X interrupts required
> before calling pci_enable_msi_block() and pci_enable_msix()
> interfaces:
> 
> 
> 	rc = pci_msix_table_size(adapter->pdev);
> 	if (rc < 0)
> 		return rc;
> 
> 	nvec = min(nvec, rc);
> 	if (nvec < FOO_DRIVER_MINIMUM_NVEC) {
> 		return -ENOSPC;
> 
> 	for (i = 0; i < nvec; i++)
> 		adapter->msix_entries[i].entry = i;
> 
> 	rc = pci_enable_msix(adapter->pdev,
> 			     adapter->msix_entries, nvec);
> 	return rc;
> 

Why not add a minimum number to pci_enable_msix(), i.e.:

pci_enable_msix(pdev, msix_entries, nvec, minvec)

... which means "nvec" is the number of interrupts *requested*, and
"minvec" is the minimum acceptable number (otherwise fail).

	-hpa

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