Provide a new interface which allows to expand the MSI-X vector space ifNot sure why some of these changes related to PCI_MSIX_EXPAND_AUTO and num_descs did not make it to the 'msi' branch.
the underlying irq domain implementation supports it.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
drivers/pci/msi/msi.c | 41 +++++++++++++++++++++++++++++++++++++++++
include/linux/pci.h | 13 +++++++++++++
2 files changed, 54 insertions(+)
--- a/drivers/pci/msi/msi.c
+++ b/drivers/pci/msi/msi.c
@@ -1025,6 +1025,47 @@ int pci_alloc_irq_vectors_affinity(struc
EXPORT_SYMBOL(pci_alloc_irq_vectors_affinity);
/**
+ * pci_msix_expand_vectors_at - Expand MSI-X interrupts for a device
+ *
+ * @dev: PCI device to operate on
+ * @at: Allocate at MSI-X index. If @at == PCI_MSI_EXPAND_AUTO
+ * the function expands automatically after the last
+ * active index.I am having trouble fully comprehending how this expansion scheme would work..
+ * @nvec: Number of vectors to allocate
+ *
+ * Expand the MSI-X vectors of a device after an initial enablement and
+ * allocation.
+ *
+ * Return: 0 if the allocation was successful, an error code otherwise.
+ */
+int pci_msix_expand_vectors_at(struct pci_dev *dev, unsigned int at, unsigned int nvec)
+{
+ struct msi_device_data *md = dev->dev.msi.data;
+ struct msi_range range = { .ndesc = nvec, };
+ unsigned int max_vecs;
+ int ret;
+
+ if (!pci_msi_enable || !dev || !dev->msix_enabled || !md)
+ return -ENOTSUPP;
+
+ if (!pci_msi_domain_supports_expand(dev))
+ return -ENOTSUPP;
+
+ max_vecs = pci_msix_vec_count(dev);
+ if (!nvec || nvec > max_vecs)
+ return -EINVAL;
+
+ range.first = at == PCI_MSIX_EXPAND_AUTO ? md->num_descs : at;
+
+ if (range.first >= max_vecs || nvec > max_vecs - range.first)
+ return -ENOSPC;
+
+ ret = msix_setup_interrupts(dev, dev->msix_base, &range, NULL, NULL, true);
+ return ret <= 0 ? ret : -ENOSPC;;
+}
+EXPORT_SYMBOL_GPL(pci_msix_expand_vectors_at);
+