PCI/MSI: Add pci_enable_msi_range() and pci_enable_msix_range()

This adds pci_enable_msi_range(), which supersedes the pci_enable_msi()
and pci_enable_msi_block() MSI interfaces.

It also adds pci_enable_msix_range(), which supersedes the
pci_enable_msix() MSI-X interface.

The old interfaces have three categories of return values:

    negative: failure; caller should not retry
    positive: failure; value indicates number of interrupts that *could*
	have been allocated, and caller may retry with a smaller request
    zero: success; at least as many interrupts allocated as requested

It is error-prone to handle these three cases correctly in drivers.

The new functions return either a negative error code or a number of
successfully allocated MSI/MSI-X interrupts, which is expected to lead to
clearer device driver code.

pci_enable_msi(), pci_enable_msi_block() and pci_enable_msix() still exist
unchanged, but are deprecated and may be removed after callers are updated.

[bhelgaas: tweak changelog]
Suggested-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Tejun Heo <tj@kernel.org>

1 files changed, 74 insertions, 0 deletions

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index bd18ecf74c55..e6bd8e57d92d 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1102,3 +1102,77 @@ void pci_msi_init_pci_dev(struct pci_dev *dev)
         if (dev->msix_cap)
                 msix_set_enable(dev, 0);
 }
+
+/**
+ * pci_enable_msi_range - configure device's MSI capability structure
+ * @dev: device to configure
+ * @minvec: minimal number of interrupts to configure
+ * @maxvec: maximum number of interrupts to configure
+ *
+ * This function tries to allocate a maximum possible number of interrupts in a
+ * range between @minvec and @maxvec. It returns a negative errno if an error
+ * occurs. If it succeeds, it returns the actual number of interrupts allocated
+ * and updates the @dev's irq member to the lowest new interrupt number;
+ * the other interrupt numbers allocated to this device are consecutive.
+ **/
+int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec)
+{
+        int nvec = maxvec;
+        int rc;
+
+        if (maxvec < minvec)
+                return -ERANGE;
+
+        do {
+                rc = pci_enable_msi_block(dev, nvec);
+                if (rc < 0) {
+                        return rc;
+                } else if (rc > 0) {
+                        if (rc < minvec)
+                                return -ENOSPC;
+                        nvec = rc;
+                }
+        } while (rc);
+
+        return nvec;
+}
+EXPORT_SYMBOL(pci_enable_msi_range);
+
+/**
+ * pci_enable_msix_range - configure device's MSI-X capability structure
+ * @dev: pointer to the pci_dev data structure of MSI-X device function
+ * @entries: pointer to an array of MSI-X entries
+ * @minvec: minimum number of MSI-X irqs requested
+ * @maxvec: maximum number of MSI-X irqs requested
+ *
+ * Setup the MSI-X capability structure of device function with a maximum
+ * possible number of interrupts in the range between @minvec and @maxvec
+ * upon its software driver call to request for MSI-X mode enabled on its
+ * hardware device function. It returns a negative errno if an error occurs.
+ * If it succeeds, it returns the actual number of interrupts allocated and
+ * indicates the successful configuration of MSI-X capability structure
+ * with new allocated MSI-X interrupts.
+ **/
+int pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries,
+                               int minvec, int maxvec)
+{
+        int nvec = maxvec;
+        int rc;
+
+        if (maxvec < minvec)
+                return -ERANGE;
+
+        do {
+                rc = pci_enable_msix(dev, entries, nvec);
+                if (rc < 0) {
+                        return rc;
+                } else if (rc > 0) {
+                        if (rc < minvec)
+                                return -ENOSPC;
+                        nvec = rc;
+                }
+        } while (rc);
+
+        return nvec;
+}
+EXPORT_SYMBOL(pci_enable_msix_range);