[PATCH V3 5/5] genirq/affinity: Document .calc_sets as required in case of multiple sets

[Ming Lei <ming.lei@redhat.com>]

Now NVMe has implemented the .calc_sets callback for caculating each
set's vectors.

For other cases of multiple IRQ sets, pre-caculating each set's vectors
before allocating IRQ vectors can't work because the whole vectors
number is unknow at that time.

So document .calc_sets as required explicitly for multiple sets.

Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/pci/msi.c         | 16 ++++++++++------
 include/linux/interrupt.h |  3 ++-
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 96978459e2a0..199d708b4099 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1036,10 +1036,12 @@ static int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
 		return -ERANGE;
 
 	/*
-	 * If the caller is passing in sets, we can't support a range of
-	 * vectors. The caller needs to handle that.
+	 * If the caller requests multiple sets of IRQs where each set
+	 * requires different affinity, it must also supply a ->calc_sets()
+	 * callback to compute vectors for each set after whole vectors are
+	 * allocated.
 	 */
-	if (affd && affd->nr_sets && minvec != maxvec)
+	if (affd && affd->nr_sets > 1 && !affd->calc_sets)
 		return -EINVAL;
 
 	if (WARN_ON_ONCE(dev->msi_enabled))
@@ -1094,10 +1096,12 @@ static int __pci_enable_msix_range(struct pci_dev *dev,
 		return -ERANGE;
 
 	/*
-	 * If the caller is passing in sets, we can't support a range of
-	 * supported vectors. The caller needs to handle that.
+	 * If the caller requests multiple sets of IRQs where each set
+	 * requires different affinity, it must also supply a ->calc_sets()
+	 * callback to compute vectors for each set after whole vectors are
+	 * allocated.
 	 */
-	if (affd && affd->nr_sets && minvec != maxvec)
+	if (affd && affd->nr_sets > 1 && !affd->calc_sets)
 		return -EINVAL;
 
 	if (WARN_ON_ONCE(dev->msix_enabled))
diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 7a27f6ba1f2f..a053f7fb0ff1 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -269,7 +269,8 @@ struct irq_affinity_notify {
  *			the MSI(-X) vector space
  * @nr_sets:		Length of passed in *sets array
  * @set_vectors:	Number of affinitized sets
- * @calc_sets:		Callback for caculating set vectors
+ * @calc_sets:		Callback for caculating set vectors, required for
+ * 			multiple irq sets.
  * @priv:		Private data of @calc_sets
  */
 struct irq_affinity {
-- 
2.9.5