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Subject[tip: irq/msi] genirq/msi: Provide a set of advanced MSI accessors and iterators
The following commit has been merged into the irq/msi branch of tip:

Commit-ID: 1046f71d7268b1680d7b044dea83c664403f6302
Gitweb: https://git.kernel.org/tip/1046f71d7268b1680d7b044dea83c664403f6302
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Mon, 06 Dec 2021 23:51:08 +01:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 16 Dec 2021 22:22:17 +01:00

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

---
include/linux/msi.h | 33 +++++++++++++++-
kernel/irq/msi.c | 96 ++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 129 insertions(+)

diff --git a/include/linux/msi.h b/include/linux/msi.h
index 69c588e..703221f 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)
diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
index 3b21e99..bc67b2c 100644
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -125,10 +125,106 @@ EXPORT_SYMBOL_GPL(msi_lock_descs);
*/
void msi_unlock_descs(struct device *dev)
{
+ /* Clear the next pointer which was cached by the iterator */
+ dev->msi.data->__next = NULL;
mutex_unlock(&dev->msi.data->mutex);
}
EXPORT_SYMBOL_GPL(msi_unlock_descs);

+static bool msi_desc_match(struct msi_desc *desc, enum msi_desc_filter filter)
+{
+ switch (filter) {
+ case MSI_DESC_ALL:
+ return true;
+ case MSI_DESC_NOTASSOCIATED:
+ return !desc->irq;
+ case MSI_DESC_ASSOCIATED:
+ return !!desc->irq;
+ }
+ WARN_ON_ONCE(1);
+ return false;
+}
+
+static struct msi_desc *msi_find_first_desc(struct device *dev, enum msi_desc_filter filter)
+{
+ struct msi_desc *desc;
+
+ list_for_each_entry(desc, dev_to_msi_list(dev), list) {
+ if (msi_desc_match(desc, filter))
+ return desc;
+ }
+ return NULL;
+}
+
+/**
+ * msi_first_desc - Get the first MSI descriptor of a device
+ * @dev: Device to operate on
+ * @filter: Descriptor state filter
+ *
+ * Must be called with the MSI descriptor mutex held, i.e. msi_lock_descs()
+ * must be invoked before the call.
+ *
+ * Return: Pointer to the first MSI descriptor matching the search
+ * criteria, NULL if none found.
+ */
+struct msi_desc *msi_first_desc(struct device *dev, enum msi_desc_filter filter)
+{
+ struct msi_desc *desc;
+
+ if (WARN_ON_ONCE(!dev->msi.data))
+ return NULL;
+
+ lockdep_assert_held(&dev->msi.data->mutex);
+
+ desc = msi_find_first_desc(dev, filter);
+ dev->msi.data->__next = desc ? list_next_entry(desc, list) : NULL;
+ return desc;
+}
+EXPORT_SYMBOL_GPL(msi_first_desc);
+
+static struct msi_desc *__msi_next_desc(struct device *dev, enum msi_desc_filter filter,
+ struct msi_desc *from)
+{
+ struct msi_desc *desc = from;
+
+ list_for_each_entry_from(desc, dev_to_msi_list(dev), list) {
+ if (msi_desc_match(desc, filter))
+ return desc;
+ }
+ return NULL;
+}
+
+/**
+ * msi_next_desc - Get the next MSI descriptor of a device
+ * @dev: Device to operate on
+ *
+ * The first invocation of msi_next_desc() has to be preceeded by a
+ * successful incovation of __msi_first_desc(). Consecutive invocations are
+ * only valid if the previous one was successful. All these operations have
+ * to be done within the same MSI mutex held region.
+ *
+ * Return: Pointer to the next MSI descriptor matching the search
+ * criteria, NULL if none found.
+ */
+struct msi_desc *msi_next_desc(struct device *dev, enum msi_desc_filter filter)
+{
+ struct msi_device_data *data = dev->msi.data;
+ struct msi_desc *desc;
+
+ if (WARN_ON_ONCE(!data))
+ return NULL;
+
+ lockdep_assert_held(&data->mutex);
+
+ if (!data->__next)
+ return NULL;
+
+ desc = __msi_next_desc(dev, filter, data->__next);
+ dev->msi.data->__next = desc ? list_next_entry(desc, list) : NULL;
+ return desc;
+}
+EXPORT_SYMBOL_GPL(msi_next_desc);
+
/**
* msi_get_virq - Return Linux interrupt number of a MSI interrupt
* @dev: Device to operate on
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