qcacmn: Properly abstract the Linux bottom half interfaces

When migrating to Linux Kernel v5.19 the following compilation error
was encountered:

i_qdf_defer.h:192:19: error: cast from 'qdf_defer_fn_t' (aka 'void (*)(void *)') to '__qdf_bh_fn_t' (aka 'void (*)(unsigned long)') converts to incompatible function type [-Werror,-Wcast-function-type]
        tasklet_init(bh, (__qdf_bh_fn_t) func, (unsigned long)arg);

This revealed the fact that the QDF bottom half abstraction was not
cleanly implemented. The current implementation freely typecasts the
abstracted signature:
	void (*func)(void *arg)
with the Linux-specific signature:
	void (*func)(unsigned long arg)

This has worked in the past since a void * and and unsigned long are
the same size and hence could be freely converted from one to another.
However the Linux Kernel now supports Call Flow Integrity which
requires that the function signatures must always exactly match.

To address this issue rewrite the bottom half abstraction to use an
intermediate dispatching function, exactly like is already done for
the deferred work abstraction.

Change-Id: I56b5a8ab9515033d8237302300fd6b55ea755633
CRs-Fixed: 3305515

qdf/linux/src/i_qdf_defer.h

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2014-2021 The Linux Foundation. All rights reserved.
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
  *
  * Permission to use, copy, modify, and/or distribute this software for
  * any purpose with or without fee is hereby granted, provided that the
@@ -30,7 +31,6 @@
 #include <qdf_status.h>
 #include <qdf_trace.h>
 
-typedef struct tasklet_struct __qdf_bh_t;
 typedef struct workqueue_struct __qdf_workqueue_t;
 
 /**
@@ -45,9 +45,41 @@ typedef struct {
 	void *arg;
 } __qdf_work_t;
 
-extern void __qdf_defer_func(struct work_struct *work);
+/**
+ * __qdf_bh_t - wrapper around the real task func
+ * @bh: Instance of the bottom half
+ * @fn: function pointer to the handler
+ * @arg: pointer to argument
+ */
+typedef struct {
+	struct tasklet_struct bh;
+	qdf_defer_fn_t fn;
+	void *arg;
+} __qdf_bh_t;
 
-typedef void (*__qdf_bh_fn_t)(unsigned long arg);
+/**
+ * __qdf_defer_func() - Linux-specific defer work handler
+ * @work: Pointer to defer work
+ *
+ * This function services all Linux-specific deferred work
+ * and dispatches them to the correct handler using the
+ * abstracted functional interface.
+ *
+ * Return: none
+ */
+void __qdf_defer_func(struct work_struct *work);
+
+/**
+ * __qdf_bh_func() - bottom half handler
+ * @arg: Pointer to bottom half abstraction
+ *
+ * This function services all Linux-specific bottom halfs
+ * and dispatches them to the correct handler using the
+ * abstracted functional interface.
+ *
+ * Return: none
+ */
+void __qdf_bh_func(unsigned long arg);
 
 /**
  * __qdf_init_work - Initialize a work/task queue, This runs in non-interrupt
@@ -184,24 +216,25 @@ static inline void __qdf_destroy_workqueue(__qdf_workqueue_t *wqueue)
  * @bh: pointer to bottom
  * @func: deferred function to run at bottom half interrupt context.
  * @arg: argument for the deferred function
+ *
  * Return: none
  */
-static inline QDF_STATUS
-__qdf_init_bh(struct tasklet_struct *bh, qdf_defer_fn_t func, void *arg)
+static inline void __qdf_init_bh(__qdf_bh_t *bh, qdf_defer_fn_t func, void *arg)
 {
-	tasklet_init(bh, (__qdf_bh_fn_t) func, (unsigned long)arg);
-	return QDF_STATUS_SUCCESS;
+	bh->fn = func;
+	bh->arg = arg;
+	tasklet_init(&bh->bh, __qdf_bh_func, (unsigned long)bh);
 }
 
 /**
  * __qdf_sched_bh - schedule a bottom half (DPC)
  * @bh: pointer to bottom
+ *
  * Return: none
  */
-static inline QDF_STATUS __qdf_sched_bh(struct tasklet_struct *bh)
+static inline void __qdf_sched_bh(__qdf_bh_t *bh)
 {
-	tasklet_schedule(bh);
-	return QDF_STATUS_SUCCESS;
+	tasklet_schedule(&bh->bh);
 }
 
 /**
@@ -220,12 +253,12 @@ static inline QDF_STATUS __qdf_disable_work(__qdf_work_t *work)
 /**
  * __qdf_disable_bh - destroy the bh (synchronous)
  * @bh: pointer to bottom
+ *
  * Return: none
  */
-static inline QDF_STATUS __qdf_disable_bh(struct tasklet_struct *bh)
+static inline void __qdf_disable_bh(__qdf_bh_t *bh)
 {
-	tasklet_kill(bh);
-	return QDF_STATUS_SUCCESS;
+	tasklet_kill(&bh->bh);
 }
 
 #endif /*_I_QDF_DEFER_H*/

qdf/linux/src/qdf_defer.c

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2014-2019,2021 The Linux Foundation. All rights reserved.
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
  *
  * Permission to use, copy, modify, and/or distribute this software for
  * any purpose with or without fee is hereby granted, provided that the
@@ -29,12 +30,6 @@
 #include <qdf_module.h>
 #include <qdf_defer.h>
 
-/**
- * __qdf_defer_func() - defer work handler
- * @work: Pointer to defer work
- *
- * Return: none
- */
 void __qdf_defer_func(struct work_struct *work)
 {
 	__qdf_work_t *ctx = container_of(work, __qdf_work_t, work);
@@ -48,6 +43,19 @@ void __qdf_defer_func(struct work_struct *work)
 }
 qdf_export_symbol(__qdf_defer_func);
 
+void __qdf_bh_func(unsigned long arg)
+{
+	__qdf_bh_t *ctx = (__qdf_bh_t *)arg;
+
+	if (!ctx->fn) {
+		QDF_TRACE(QDF_MODULE_ID_QDF, QDF_TRACE_LEVEL_ERROR,
+			  "No callback registered !!");
+		return;
+	}
+	ctx->fn(ctx->arg);
+}
+qdf_export_symbol(__qdf_bh_func);
+
 #ifdef ENHANCED_OS_ABSTRACTION
 void
 qdf_create_bh(qdf_bh_t  *bh, qdf_defer_fn_t  func, void  *arg)