[PATCH v6 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 functions to do eventfds binding
with given interrupts.

Sub feature drivers are expected to use XXX_GET_IRQ_NUM to query irq
info, and XXX_SET_IRQ to set eventfds for interrupts. This patch also
introduces helper functions for these 2 ioctls.

Signed-off-by: Luwei Kang <luwei.kang@xxxxxxxxx>
Signed-off-by: Wu Hao <hao.wu@xxxxxxxxx>
Signed-off-by: Xu Yilun <yilun.xu@xxxxxxxxx>
Reviewed-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Acked-by: Wu Hao <hao.wu@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()
v3: Improve comments of dfl_fpga_set_irq_triggers()
    refines code for dfl_fpga_set_irq_triggers, delete local variable j
v4: Introduce 2 helper functions to help handle the XXX_GET_IRQ_NUM &
    XXX_SET_IRQ ioctls for sub feature drivers.
v5: Some minor fix for Hao's comments
v6: Remove unnecessary type casting
---
 drivers/fpga/dfl.c            | 155 ++++++++++++++++++++++++++++++++++++++++++
 drivers/fpga/dfl.h            |  17 +++++
 include/uapi/linux/fpga-dfl.h |  13 ++++
 3 files changed, 185 insertions(+)

diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
index 02c1ec4..125369c 100644
--- a/drivers/fpga/dfl.c
+++ b/drivers/fpga/dfl.c
@@ -10,7 +10,9 @@
  *   Wu Hao <hao.wu@xxxxxxxxx>
  *   Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
  */
+#include <linux/fpga-dfl.h>
 #include <linux/module.h>
+#include <linux/uaccess.h>
 
 #include "dfl.h"
 
@@ -534,6 +536,7 @@ static int build_info_commit_dev(struct build_feature_devs_info *binfo)
 		unsigned int i;
 
 		/* save resource information for each feature */
+		feature->dev = fdev;
 		feature->id = finfo->fid;
 		feature->resource_index = index;
 		feature->ioaddr = finfo->ioaddr;
@@ -1394,6 +1397,158 @@ 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), 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. unbind related irq if fds[n] is negative.
+ *	 unbind "count" specified number of irqs if fds ptr is NULL.
+ *
+ * Bind given eventfds with irqs in this dfl sub feature. Unbind related irq if
+ * fds[n] is negative. Unbind "count" specified number of irqs if fds ptr is
+ * NULL.
+ *
+ * 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;
+	int ret = 0;
+
+	if (start + count < start || start + count > feature->nr_irqs)
+		return -EINVAL;
+
+	for (i = 0; i < count; i++) {
+		int fd = fds ? fds[i] : -1;
+
+		ret = do_set_irq_trigger(feature, start + i, fd);
+		if (ret) {
+			while (i--)
+				do_set_irq_trigger(feature, start + i, -1);
+			break;
+		}
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dfl_fpga_set_irq_triggers);
+
+/**
+ * dfl_feature_ioctl_get_num_irqs - dfl feature _GET_IRQ_NUM ioctl interface.
+ * @pdev: the feature device which has the sub feature
+ * @feature: the dfl sub feature
+ * @arg: ioctl argument
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+long dfl_feature_ioctl_get_num_irqs(struct platform_device *pdev,
+				    struct dfl_feature *feature,
+				    unsigned long arg)
+{
+	return put_user(feature->nr_irqs, (__u32 __user *)arg);
+}
+EXPORT_SYMBOL_GPL(dfl_feature_ioctl_get_num_irqs);
+
+/**
+ * dfl_feature_ioctl_set_irq - dfl feature _SET_IRQ ioctl interface.
+ * @pdev: the feature device which has the sub feature
+ * @feature: the dfl sub feature
+ * @arg: ioctl argument
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+long dfl_feature_ioctl_set_irq(struct platform_device *pdev,
+			       struct dfl_feature *feature,
+			       unsigned long arg)
+{
+	struct dfl_feature_platform_data *pdata = dev_get_platdata(&pdev->dev);
+	struct dfl_fpga_irq_set hdr;
+	s32 *fds;
+	long ret;
+
+	if (!feature->nr_irqs)
+		return -ENOENT;
+
+	if (copy_from_user(&hdr, (void __user *)arg, sizeof(hdr)))
+		return -EFAULT;
+
+	if (!hdr.count || (hdr.start + hdr.count > feature->nr_irqs) ||
+	    (hdr.start + hdr.count < hdr.start))
+		return -EINVAL;
+
+	fds = memdup_user((void __user *)(arg + sizeof(hdr)),
+			  hdr.count * sizeof(s32));
+	if (IS_ERR(fds))
+		return PTR_ERR(fds);
+
+	mutex_lock(&pdata->lock);
+	ret = dfl_fpga_set_irq_triggers(feature, hdr.start, hdr.count, fds);
+	mutex_unlock(&pdata->lock);
+
+	kfree(fds);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dfl_feature_ioctl_set_irq);
+
 static void __exit dfl_fpga_exit(void)
 {
 	dfl_chardev_uinit();
diff --git a/drivers/fpga/dfl.h b/drivers/fpga/dfl.h
index a3c9e4a..632e733 100644
--- a/drivers/fpga/dfl.h
+++ b/drivers/fpga/dfl.h
@@ -17,7 +17,9 @@
 #include <linux/bitfield.h>
 #include <linux/cdev.h>
 #include <linux/delay.h>
+#include <linux/eventfd.h>
 #include <linux/fs.h>
+#include <linux/interrupt.h>
 #include <linux/iopoll.h>
 #include <linux/io-64-nonatomic-lo-hi.h>
 #include <linux/platform_device.h>
@@ -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
@@ -232,6 +239,7 @@ struct dfl_feature_irq_ctx {
  * @priv: priv data of this feature.
  */
 struct dfl_feature {
+	struct platform_device *dev;
 	u64 id;
 	int resource_index;
 	void __iomem *ioaddr;
@@ -508,4 +516,13 @@ 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);
+long dfl_feature_ioctl_get_num_irqs(struct platform_device *pdev,
+				    struct dfl_feature *feature,
+				    unsigned long arg);
+long dfl_feature_ioctl_set_irq(struct platform_device *pdev,
+			       struct dfl_feature *feature,
+			       unsigned long arg);
+
 #endif /* __FPGA_DFL_H */
diff --git a/include/uapi/linux/fpga-dfl.h b/include/uapi/linux/fpga-dfl.h
index ec70a0746..7331350 100644
--- a/include/uapi/linux/fpga-dfl.h
+++ b/include/uapi/linux/fpga-dfl.h
@@ -151,6 +151,19 @@ struct dfl_fpga_port_dma_unmap {
 
 #define DFL_FPGA_PORT_DMA_UNMAP		_IO(DFL_FPGA_MAGIC, DFL_PORT_BASE + 4)
 
+/**
+ * struct dfl_fpga_irq_set - the argument for DFL_FPGA_XXX_SET_IRQ ioctl.
+ *
+ * @start: Index of the first irq.
+ * @count: The number of eventfd handler.
+ * @evtfds: Eventfd handlers.
+ */
+struct dfl_fpga_irq_set {
+	__u32 start;
+	__u32 count;
+	__s32 evtfds[];
+};
+
 /* IOCTLs for FME file descriptor */
 
 /**
-- 
2.7.4