[PATCH v2 6/7] ocxl: move event_fd handling to frontend

["Alastair D'Silva" <alastair@au1.ibm.com>]

From: Alastair D'Silva <alastair@d-silva.org>

Event_fd is only used in the driver frontend, so it does not
need to exist in the backend code. Relocate it to the frontend
and provide an opaque mechanism for consumers instead.

Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
---
 drivers/misc/ocxl/afu_irq.c       | 69 +++++++++++++++++--------------
 drivers/misc/ocxl/file.c          | 22 +++++++++-
 drivers/misc/ocxl/ocxl_internal.h |  5 ---
 include/misc/ocxl.h               | 46 +++++++++++++++++++++
 4 files changed, 104 insertions(+), 38 deletions(-)

diff --git a/drivers/misc/ocxl/afu_irq.c b/drivers/misc/ocxl/afu_irq.c
index 2d410cd6f817..f23cd585e737 100644
--- a/drivers/misc/ocxl/afu_irq.c
+++ b/drivers/misc/ocxl/afu_irq.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0+
 // Copyright 2017 IBM Corp.
 #include <linux/interrupt.h>
-#include <linux/eventfd.h>
+#include <asm/pnv-ocxl.h>
 #include "ocxl_internal.h"
 #include "trace.h"
 
@@ -11,7 +11,9 @@ struct afu_irq {
 	unsigned int virq;
 	char *name;
 	u64 trigger_page;
-	struct eventfd_ctx *ev_ctx;
+	irqreturn_t (*handler)(void *private);
+	void (*free_private)(void *private);
+	void *private;
 };
 
 int ocxl_irq_offset_to_id(struct ocxl_context *ctx, u64 offset)
@@ -24,14 +26,42 @@ u64 ocxl_irq_id_to_offset(struct ocxl_context *ctx, int irq_id)
 	return ctx->afu->irq_base_offset + (irq_id << PAGE_SHIFT);
 }
 
+int ocxl_irq_set_handler(struct ocxl_context *ctx, int irq_id,
+		irqreturn_t (*handler)(void *private),
+		void (*free_private)(void *private),
+		void *private)
+{
+	struct afu_irq *irq;
+	int rc;
+
+	mutex_lock(&ctx->irq_lock);
+	irq = idr_find(&ctx->irq_idr, irq_id);
+	if (!irq) {
+		rc = -EINVAL;
+		goto unlock;
+	}
+
+	irq->handler = handler;
+	irq->private = private;
+
+	rc = 0;
+	goto unlock;
+
+unlock:
+	mutex_unlock(&ctx->irq_lock);
+	return rc;
+}
+
 static irqreturn_t afu_irq_handler(int virq, void *data)
 {
 	struct afu_irq *irq = (struct afu_irq *) data;
 
 	trace_ocxl_afu_irq_receive(virq);
-	if (irq->ev_ctx)
-		eventfd_signal(irq->ev_ctx, 1);
-	return IRQ_HANDLED;
+
+	if (irq->handler)
+		return irq->handler(irq->private);
+
+	return IRQ_HANDLED; // Just drop it on the ground
 }
 
 static int setup_afu_irq(struct ocxl_context *ctx, struct afu_irq *irq)
@@ -126,8 +156,8 @@ static void afu_irq_free(struct afu_irq *irq, struct ocxl_context *ctx)
 				ocxl_irq_id_to_offset(ctx, irq->id),
 				1 << PAGE_SHIFT, 1);
 	release_afu_irq(irq);
-	if (irq->ev_ctx)
-		eventfd_ctx_put(irq->ev_ctx);
+	if (irq->free_private)
+		irq->free_private(irq->private);
 	ocxl_link_free_irq(ctx->afu->fn->link, irq->hw_irq);
 	kfree(irq);
 }
@@ -160,31 +190,6 @@ void ocxl_afu_irq_free_all(struct ocxl_context *ctx)
 	mutex_unlock(&ctx->irq_lock);
 }
 
-int ocxl_afu_irq_set_fd(struct ocxl_context *ctx, int irq_id, int eventfd)
-{
-	struct afu_irq *irq;
-	struct eventfd_ctx *ev_ctx;
-	int rc = 0;
-
-	mutex_lock(&ctx->irq_lock);
-	irq = idr_find(&ctx->irq_idr, irq_id);
-	if (!irq) {
-		rc = -EINVAL;
-		goto unlock;
-	}
-
-	ev_ctx = eventfd_ctx_fdget(eventfd);
-	if (IS_ERR(ev_ctx)) {
-		rc = -EINVAL;
-		goto unlock;
-	}
-
-	irq->ev_ctx = ev_ctx;
-unlock:
-	mutex_unlock(&ctx->irq_lock);
-	return rc;
-}
-
 u64 ocxl_afu_irq_get_addr(struct ocxl_context *ctx, int irq_id)
 {
 	struct afu_irq *irq;
diff --git a/drivers/misc/ocxl/file.c b/drivers/misc/ocxl/file.c
index d13297336253..42214b0c956a 100644
--- a/drivers/misc/ocxl/file.c
+++ b/drivers/misc/ocxl/file.c
@@ -3,6 +3,7 @@
 #include <linux/fs.h>
 #include <linux/poll.h>
 #include <linux/sched/signal.h>
+#include <linux/eventfd.h>
 #include <linux/uaccess.h>
 #include <uapi/misc/ocxl.h>
 #include <asm/reg.h>
@@ -191,11 +192,27 @@ static long afu_ioctl_get_features(struct ocxl_context *ctx,
 			x == OCXL_IOCTL_GET_FEATURES ? "GET_FEATURES" :	\
 			"UNKNOWN")
 
+static irqreturn_t irq_handler(void *private)
+{
+	struct eventfd_ctx *ev_ctx = private;
+
+	eventfd_signal(ev_ctx, 1);
+	return IRQ_HANDLED;
+}
+
+static void irq_free(void *private)
+{
+	struct eventfd_ctx *ev_ctx = private;
+
+	eventfd_ctx_put(ev_ctx);
+}
+
 static long afu_ioctl(struct file *file, unsigned int cmd,
 		unsigned long args)
 {
 	struct ocxl_context *ctx = file->private_data;
 	struct ocxl_ioctl_irq_fd irq_fd;
+	struct eventfd_ctx *ev_ctx;
 	int irq_id;
 	u64 irq_offset;
 	long rc;
@@ -247,7 +264,10 @@ static long afu_ioctl(struct file *file, unsigned int cmd,
 		if (irq_fd.reserved)
 			return -EINVAL;
 		irq_id = ocxl_irq_offset_to_id(ctx, irq_fd.irq_offset);
-		rc = ocxl_afu_irq_set_fd(ctx, irq_id, irq_fd.eventfd);
+		ev_ctx = eventfd_ctx_fdget(irq_fd.eventfd);
+		if (!ev_ctx)
+			return -EFAULT;
+		rc = ocxl_irq_set_handler(ctx, irq_id, irq_handler, irq_free, ev_ctx);
 		break;
 
 	case OCXL_IOCTL_GET_METADATA:
diff --git a/drivers/misc/ocxl/ocxl_internal.h b/drivers/misc/ocxl/ocxl_internal.h
index 871155b464da..f3775223f4b1 100644
--- a/drivers/misc/ocxl/ocxl_internal.h
+++ b/drivers/misc/ocxl/ocxl_internal.h
@@ -142,12 +142,7 @@ void ocxl_sysfs_unregister_afu(struct ocxl_afu *afu);
 
 int ocxl_irq_offset_to_id(struct ocxl_context *ctx, u64 offset);
 u64 ocxl_irq_id_to_offset(struct ocxl_context *ctx, int irq_id);
-int ocxl_afu_irq_alloc(struct ocxl_context *ctx, int *irq_id);
-int ocxl_afu_irq_free(struct ocxl_context *ctx, int irq_id);
 void ocxl_afu_irq_free_all(struct ocxl_context *ctx);
-int ocxl_afu_irq_set_fd(struct ocxl_context *ctx, int irq_id,
-			int eventfd);
-u64 ocxl_afu_irq_get_addr(struct ocxl_context *ctx, int irq_id);
 
 /**
  * Free an AFU
diff --git a/include/misc/ocxl.h b/include/misc/ocxl.h
index a5e94da6c8db..790b25987d9a 100644
--- a/include/misc/ocxl.h
+++ b/include/misc/ocxl.h
@@ -161,6 +161,52 @@ int ocxl_context_attach(struct ocxl_context *ctx, u64 amr,
  */
 int ocxl_context_detach(struct ocxl_context *ctx);
 
+// AFU IRQs
+
+/**
+ * Allocate an IRQ associated with an AFU context
+ * @ctx: the AFU context
+ * @irq_id: out, the IRQ ID
+ *
+ * Returns 0 on success, negative on failure
+ */
+extern int ocxl_afu_irq_alloc(struct ocxl_context *ctx, int *irq_id);
+
+/**
+ * Frees an IRQ associated with an AFU context
+ * @ctx: the AFU context
+ * @irq_id: the IRQ ID
+ *
+ * Returns 0 on success, negative on failure
+ */
+extern int ocxl_afu_irq_free(struct ocxl_context *ctx, int irq_id);
+
+/**
+ * Gets the address of the trigger page for an IRQ
+ * This can then be provided to an AFU which will write to that
+ * page to trigger the IRQ.
+ * @ctx: The AFU context that the IRQ is associated with
+ * @irq_id: The IRQ ID
+ *
+ * returns the trigger page address, or 0 if the IRQ is not valid
+ */
+extern u64 ocxl_afu_irq_get_addr(struct ocxl_context *ctx, int irq_id);
+
+/**
+ * Provide a callback to be called when an IRQ is triggered
+ * @ctx: The AFU context that the IRQ is associated with
+ * @irq_id: The IRQ ID
+ * @handler: the callback to be called when the IRQ is triggered
+ * @free_private: the callback to be called when the IRQ is freed
+ * @private: Private data to be passed to the callbacks
+ *
+ * Returns 0 on success, negative on failure
+ */
+int ocxl_irq_set_handler(struct ocxl_context *ctx, int irq_id,
+		irqreturn_t (*handler)(void *private),
+		void (*free_private)(void *private),
+		void *private);
+
 // AFU Metadata
 
 /**
-- 
2.20.1