Commit 61af6929 authored by Marc Zyngier's avatar Marc Zyngier Committed by Lorenzo Pieralisi
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PCI/MSI: Document the various ways of ending up with NO_MSI 

We have now three ways of ending up with NO_MSI being set.
Document them.

Link: https://lore.kernel.org/r/20210330151145.997953-14-maz@kernel.org


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Signed-off-by: default avatarLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: default avatarBjorn Helgaas <bhelgaas@google.com>
parent 645e9c38

drivers/pci/msi.c

+9 −2
Original line number Diff line number Diff line
@@ -871,8 +871,15 @@ static int pci_msi_supported(struct pci_dev *dev, int nvec) 
	 * Any bridge which does NOT route MSI transactions from its

	 * secondary bus to its primary bus must set NO_MSI flag on

	 * the secondary pci_bus.

	 * We expect only arch-specific PCI host bus controller driver

	 * or quirks for specific PCI bridges to be setting NO_MSI.

	 *

	 * The NO_MSI flag can either be set directly by:

	 * - arch-specific PCI host bus controller drivers (deprecated)

	 * - quirks for specific PCI bridges

	 *

	 * or indirectly by platform-specific PCI host bridge drivers by

	 * advertising the 'msi_domain' property, which results in

	 * the NO_MSI flag when no MSI domain is found for this bridge

	 * at probe time.

	 */

	for (bus = dev->bus; bus; bus = bus->parent)

		if (bus->bus_flags & PCI_BUS_FLAGS_NO_MSI)