genirq/msi: Provide a set of advanced MSI accessors and iterators

In preparation for dynamic handling of MSI-X interrupts provide a new set
of MSI descriptor accessor functions and iterators. They are benefitial per
se as they allow to cleanup quite some code in various MSI domain
implementations.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20211206210747.818635078@linutronix.de

1 files changed, 33 insertions, 0 deletions

diff --git a/include/linux/msi.h b/include/linux/msi.h
index 69c588efe85b..703221f7e9ea 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -140,6 +140,18 @@ struct msi_desc {
 	struct pci_msi_desc		pci;
 };
 
+/*
+ * Filter values for the MSI descriptor iterators and accessor functions.
+ */
+enum msi_desc_filter {
+	/* All descriptors */
+	MSI_DESC_ALL,
+	/* Descriptors which have no interrupt associated */
+	MSI_DESC_NOTASSOCIATED,
+	/* Descriptors which have an interrupt associated */
+	MSI_DESC_ASSOCIATED,
+};
+
 /**
  * msi_device_data - MSI per device data
  * @properties:		MSI properties which are interesting to drivers
@@ -147,6 +159,7 @@ struct msi_desc {
  * @platform_data:	Platform-MSI specific data
  * @list:		List of MSI descriptors associated to the device
  * @mutex:		Mutex protecting the MSI list
+ * @__next:		Cached pointer to the next entry for iterators
  */
 struct msi_device_data {
 	unsigned long			properties;
@@ -154,6 +167,7 @@ struct msi_device_data {
 	struct platform_msi_priv_data	*platform_data;
 	struct list_head		list;
 	struct mutex			mutex;
+	struct msi_desc			*__next;
 };
 
 int msi_setup_device_data(struct device *dev);
@@ -162,6 +176,25 @@ unsigned int msi_get_virq(struct device *dev, unsigned int index);
 void msi_lock_descs(struct device *dev);
 void msi_unlock_descs(struct device *dev);
 
+struct msi_desc *msi_first_desc(struct device *dev, enum msi_desc_filter filter);
+struct msi_desc *msi_next_desc(struct device *dev, enum msi_desc_filter filter);
+
+/**
+ * msi_for_each_desc - Iterate the MSI descriptors
+ *
+ * @desc:	struct msi_desc pointer used as iterator
+ * @dev:	struct device pointer - device to iterate
+ * @filter:	Filter for descriptor selection
+ *
+ * Notes:
+ *  - The loop must be protected with a msi_lock_descs()/msi_unlock_descs()
+ *    pair.
+ *  - It is safe to remove a retrieved MSI descriptor in the loop.
+ */
+#define msi_for_each_desc(desc, dev, filter)			\
+	for ((desc) = msi_first_desc((dev), (filter)); (desc);	\
+	     (desc) = msi_next_desc((dev), (filter)))
+
 /* Helpers to hide struct msi_desc implementation details */
 #define msi_desc_to_dev(desc)		((desc)->dev)
 #define dev_to_msi_list(dev)		(&(dev)->msi.data->list)