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Date: Thu, 10 Oct 2013 19:17:18 -0400
From: Mark Lord <kernel@...rt.ca>
To: Alexander Gordeev <agordeev@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>
CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
Ralf Baechle <ralf@...ux-mips.org>,
Michael Ellerman <michael@...erman.id.au>,
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, Inc." <pv-drivers@...are.com>, linux-scsi@...r.kernel.org
Subject: Re: [PATCH RFC 00/77] Re-design MSI/MSI-X interrupts enablement pattern
Just to help us all understand "the loop" issue..
Here's an example of driver code which uses the existing MSI-X interfaces,
for a device which can work with either 16, 8, 4, 2, or 1 MSI-X interrupt.
This is from a new driver I'm working on right now:
static int xx_alloc_msix_irqs (struct xx_dev *dev, int nvec)
{
xx_disable_all_irqs(dev);
do {
if (nvec < 2)
xx_prep_for_1_msix_vector(dev);
else if (nvec < 4)
xx_prep_for_2_msix_vectors(dev);
else if (nvec < 8)
xx_prep_for_4_msix_vectors(dev);
else if (nvec < 16)
xx_prep_for_8_msix_vectors(dev);
else
xx_prep_for_16_msix_vectors(dev);
nvec = pci_enable_msix(dev->pdev, dev->irqs, dev->num_vectors);
} while (nvec > 0);
if (nvec) {
kerr(dev->name, "pci_enable_msix() failed, err=%d", nvec);
dev->num_vectors = 0;
return nvec;
}
return 0; /* success */
}
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