[PATCH v2 3/7] fpga: dfl: introduce interrupt trigger setting API

[Xu Yilun]

FPGA user applications may be interested in interrupts generated by
DFL features. For example, users can implement their own FPGA
logics with interrupts enabled in AFU (Accelerated Function Unit,
dynamic region of DFL based FPGA). So user applications need to be
notified to handle these interrupts.

In order to allow userspace applications to monitor interrupts,
driver requires userspace to provide eventfds as interrupt
notification channels. Applications then poll/select on the eventfds
to get notified.

This patch introduces a generic helper function for sub features to
do eventfds binding with given interrupts.

Signed-off-by: Luwei Kang <luwei.kang@xxxxxxxxx>
Signed-off-by: Wu Hao <hao.wu@xxxxxxxxx>
Signed-off-by: Xu Yilun <yilun.xu@xxxxxxxxx>
----
v2: use unsigned int instead of int for irq array indexes in
    dfl_fpga_set_irq_triggers()
    Improves comments for NULL fds param in dfl_fpga_set_irq_triggers()
---
 drivers/fpga/dfl.c | 95 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/fpga/dfl.h | 11 +++++++
 2 files changed, 106 insertions(+)

diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
index 28e2cd8..8dcc4e2 100644
--- a/drivers/fpga/dfl.c
+++ b/drivers/fpga/dfl.c
@@ -535,6 +535,7 @@ static int build_info_commit_dev(struct build_feature_devs_info *binfo)
 		int i;
 
 		/* save resource information for each feature */
+		feature->dev = fdev;
 		feature->id = finfo->fid;
 		feature->resource_index = index;
 		feature->ioaddr = finfo->ioaddr;
@@ -1385,6 +1386,100 @@ int dfl_fpga_cdev_config_ports_vf(struct dfl_fpga_cdev *cdev, int num_vfs)
 }
 EXPORT_SYMBOL_GPL(dfl_fpga_cdev_config_ports_vf);
 
+static irqreturn_t dfl_irq_handler(int irq, void *arg)
+{
+	struct eventfd_ctx *trigger = arg;
+
+	eventfd_signal(trigger, 1);
+	return IRQ_HANDLED;
+}
+
+static int do_set_irq_trigger(struct dfl_feature *feature, unsigned int idx,
+			      int fd)
+{
+	struct platform_device *pdev = feature->dev;
+	struct eventfd_ctx *trigger;
+	int irq, ret;
+
+	if (idx >= feature->nr_irqs)
+		return -EINVAL;
+
+	irq = feature->irq_ctx[idx].irq;
+
+	if (feature->irq_ctx[idx].trigger) {
+		free_irq(irq, feature->irq_ctx[idx].trigger);
+		kfree(feature->irq_ctx[idx].name);
+		eventfd_ctx_put(feature->irq_ctx[idx].trigger);
+		feature->irq_ctx[idx].trigger = NULL;
+	}
+
+	if (fd < 0)
+		return 0;
+
+	feature->irq_ctx[idx].name =
+		kasprintf(GFP_KERNEL, "fpga-irq[%u](%s-%llx)", idx,
+			  dev_name(&pdev->dev),
+			  (unsigned long long)feature->id);
+	if (!feature->irq_ctx[idx].name)
+		return -ENOMEM;
+
+	trigger = eventfd_ctx_fdget(fd);
+	if (IS_ERR(trigger)) {
+		ret = PTR_ERR(trigger);
+		goto free_name;
+	}
+
+	ret = request_irq(irq, dfl_irq_handler, 0,
+			  feature->irq_ctx[idx].name, trigger);
+	if (!ret) {
+		feature->irq_ctx[idx].trigger = trigger;
+		return ret;
+	}
+
+	eventfd_ctx_put(trigger);
+free_name:
+	kfree(feature->irq_ctx[idx].name);
+
+	return ret;
+}
+
+/**
+ * dfl_fpga_set_irq_triggers - set eventfd triggers for dfl feature interrupts
+ *
+ * @feature: dfl sub feature.
+ * @start: start of irq index in this dfl sub feature.
+ * @count: number of irqs.
+ * @fds: eventfds to bind with irqs.
+ *
+ * Bind given eventfds with irqs in this dfl sub feature. Use NULL or negative
+ * fds as parameter to unbind irqs.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int dfl_fpga_set_irq_triggers(struct dfl_feature *feature, unsigned int start,
+			      unsigned int count, int32_t *fds)
+{
+	unsigned int i, j;
+	int ret = 0;
+
+	if (start + count < start || start + count > feature->nr_irqs)
+		return -EINVAL;
+
+	for (i = 0, j = start; i < count && !ret; i++, j++) {
+		int fd = fds ? fds[i] : -1;
+
+		ret = do_set_irq_trigger(feature, j, fd);
+	}
+
+	if (ret) {
+		for (--j; j >= start; j--)
+			do_set_irq_trigger(feature, j, -1);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dfl_fpga_set_irq_triggers);
+
 static void __exit dfl_fpga_exit(void)
 {
 	dfl_chardev_uinit();
diff --git a/drivers/fpga/dfl.h b/drivers/fpga/dfl.h
index 6a498cd..6b60077 100644
--- a/drivers/fpga/dfl.h
+++ b/drivers/fpga/dfl.h
@@ -24,6 +24,8 @@
 #include <linux/slab.h>
 #include <linux/uuid.h>
 #include <linux/fpga/fpga-region.h>
+#include <linux/interrupt.h>
+#include <linux/eventfd.h>
 
 /* maximum supported number of ports */
 #define MAX_DFL_FPGA_PORT_NUM 4
@@ -213,14 +215,19 @@ struct dfl_feature_driver {
  * struct dfl_feature_irq_ctx - dfl private feature interrupt context
  *
  * @irq: Linux IRQ number of this interrupt.
+ * @trigger: eventfd context to signal when interrupt happens.
+ * @name: irq name needed when requesting irq.
  */
 struct dfl_feature_irq_ctx {
 	int irq;
+	struct eventfd_ctx *trigger;
+	char *name;
 };
 
 /**
  * struct dfl_feature - sub feature of the feature devices
  *
+ * @dev: ptr to pdev of the feature device which has the sub feature.
  * @id: sub feature id.
  * @resource_index: each sub feature has one mmio resource for its registers.
  *		    this index is used to find its mmio resource from the
@@ -231,6 +238,7 @@ struct dfl_feature_irq_ctx {
  * @ops: ops of this sub feature.
  */
 struct dfl_feature {
+	struct platform_device *dev;
 	u64 id;
 	int resource_index;
 	void __iomem *ioaddr;
@@ -506,4 +514,7 @@ int dfl_fpga_cdev_release_port(struct dfl_fpga_cdev *cdev, int port_id);
 int dfl_fpga_cdev_assign_port(struct dfl_fpga_cdev *cdev, int port_id);
 void dfl_fpga_cdev_config_ports_pf(struct dfl_fpga_cdev *cdev);
 int dfl_fpga_cdev_config_ports_vf(struct dfl_fpga_cdev *cdev, int num_vf);
+
+int dfl_fpga_set_irq_triggers(struct dfl_feature *feature, unsigned int start,
+			      unsigned int count, int32_t *fds);
 #endif /* __FPGA_DFL_H */
-- 
2.7.4