[PATCH 2/7] backports: Fix pci_alloc_irq_vectors() backport

[Hauke Mehrtens <hauke@hauke-m.de>]

Upstream commit: 55039329e10adc511eabb7cf015d88620bf49176

This copies the pci_alloc_irq_vectors() function from kernel 4.9 and
replaces the __pci_enable_msi{x}_range() calls with calls to
pci_enable_msi{x}_range(), these were backported to kernel versions <
3.14, so no need to handle the older kernels specially here.

This also adds support for MSIx IRQs and adds the PCI_IRQ_* defines.

Fixes: 162a6b312f1b ("add support for pci_alloc_irq_vectors")
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Cc: Omer Dagan <omer.dagan@tandemg.com>
---
 backport/backport-include/linux/pci.h |  8 ++++++
 backport/compat/backport-4.8.c        | 49 +++++++++++++++++++++++++----------
 2 files changed, 44 insertions(+), 13 deletions(-)

diff --git a/backport/backport-include/linux/pci.h b/backport/backport-include/linux/pci.h
index 531f5a47..3a141bf3 100644
--- a/backport/backport-include/linux/pci.h
+++ b/backport/backport-include/linux/pci.h
@@ -224,4 +224,12 @@ static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
 
 #endif/* <4.9.0 but not >= 3.12.69, 4.4.37, 4.8.13 */
 
+#ifndef PCI_IRQ_LEGACY
+#define PCI_IRQ_LEGACY		(1 << 0) /* Allow legacy interrupts */
+#define PCI_IRQ_MSI		(1 << 1) /* Allow MSI interrupts */
+#define PCI_IRQ_MSIX		(1 << 2) /* Allow MSI-X interrupts */
+#define PCI_IRQ_ALL_TYPES \
+	(PCI_IRQ_LEGACY | PCI_IRQ_MSI | PCI_IRQ_MSIX)
+#endif
+
 #endif /* _BACKPORT_LINUX_PCI_H */
diff --git a/backport/compat/backport-4.8.c b/backport/compat/backport-4.8.c
index a53e39c9..11b2e7d7 100644
--- a/backport/compat/backport-4.8.c
+++ b/backport/compat/backport-4.8.c
@@ -148,25 +148,48 @@ EXPORT_SYMBOL_GPL(cdc_parse_cdc_header);
 
 #ifdef CONFIG_PCI
 #ifdef CONFIG_PCI_MSI
+
+/**
+ * pci_alloc_irq_vectors - allocate multiple IRQs for a device
+ * @dev:		PCI device to operate on
+ * @min_vecs:		minimum number of vectors required (must be >= 1)
+ * @max_vecs:		maximum (desired) number of vectors
+ * @flags:		flags or quirks for the allocation
+ *
+ * Allocate up to @max_vecs interrupt vectors for @dev, using MSI-X or MSI
+ * vectors if available, and fall back to a single legacy vector
+ * if neither is available.  Return the number of vectors allocated,
+ * (which might be smaller than @max_vecs) if successful, or a negative
+ * error code on error. If less than @min_vecs interrupt vectors are
+ * available for @dev the function will fail with -ENOSPC.
+ *
+ * To get the Linux IRQ number used for a vector that can be passed to
+ * request_irq() use the pci_irq_vector() helper.
+ */
 int pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
 		unsigned int max_vecs, unsigned int flags)
 {
-	int res;
-	int msi_nvect = max_vecs;
+	int vecs = -ENOSPC;
 
-	if (max_vecs < min_vecs)
-		return -ERANGE;
+	if (flags & PCI_IRQ_MSIX) {
+		vecs = pci_enable_msix_range(dev, NULL, min_vecs, max_vecs);
+		if (vecs > 0)
+			return vecs;
+	}
+
+	if (flags & PCI_IRQ_MSI) {
+		vecs = pci_enable_msi_range(dev, min_vecs, max_vecs);
+		if (vecs > 0)
+			return vecs;
+	}
 
-#if LINUX_VERSION_IS_LESS(3,15,0)
-	res = pci_enable_msi_block(dev, msi_nvect);
-	if (res == 0) {
-		return msi_nvect;
+	/* use legacy irq if allowed */
+	if ((flags & PCI_IRQ_LEGACY) && min_vecs == 1) {
+		pci_intx(dev, 1);
+		return 1;
 	}
-#else
-	res = pci_enable_msi_range(dev, msi_nvect, msi_nvect);
-	return msi_nvect;
-#endif /*LINUX_VERSION_IS_LESS(3,15,0)*/
-	return -ENOSPC;
+
+	return vecs;
 }
 EXPORT_SYMBOL_GPL(pci_alloc_irq_vectors);
 #endif /* CONFIG_PCI_MSI */
-- 
2.11.0

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