coding guidelines: partially comply with MISRA C:2012 essential types rules.

In particular:

- use bool when the data nature is Boolean;

- use explicit comparison with 0 or NULL;

- avoid mixing signed and unsigned integers in computations and
  comparisons;

- avoid mixing enumerations with integers: when this is unavoidable,
  always convert enums to integers and not the other way around;

- avoid mixing characters with integers;

- ensure computations are done in the destination precision;

- added /*? comments when the developer intentions are not clear;

- added U suffix to unsigned constants (except for the CONFIG_* macro
  constants, as they cannot be changed and then their use as unsigned
  constants should be prefixed with a cast).

Violations for rules 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8,
11.7, 12.2, 14.4 and 16.7 in the reference builds have been reduced
from 67818 to 60.  The commit cannot be divided on a per-rule basis
due to numerous cross-dependencies between changes.

Signed-off-by: Abramo Bagnara <abramo.bagnara@bugseng.com>

Author: Abramo-Bagnara

arch/arc/core/mpu/arc_core_mpu.c

@@ -35,7 +35,7 @@ int arch_mem_domain_max_partitions_get(void)
 /*
  * Validate the given buffer is user accessible or not
  */
-int arch_buffer_validate(void *addr, size_t size, int write)
+int arch_buffer_validate(void *addr, size_t size, bool write)
 {
 	return arc_core_mpu_buffer_validate(addr, size, write);
 }

arch/arc/core/mpu/arc_mpu_common_internal.h

@@ -207,7 +207,7 @@ int arc_core_mpu_get_max_domain_partition_regions(void)
 /**
  * @brief validate the given buffer is user accessible or not
  */
-int arc_core_mpu_buffer_validate(void *addr, size_t size, int write)
+int arc_core_mpu_buffer_validate(void *addr, size_t size, bool write)
 {
 	/*
 	 * For ARC MPU, smaller region number takes priority.

arch/arc/core/mpu/arc_mpu_v4_internal.h

@@ -779,7 +779,7 @@ int arc_core_mpu_get_max_domain_partition_regions(void)
 /**
  * @brief validate the given buffer is user accessible or not
  */
-int arc_core_mpu_buffer_validate(void *addr, size_t size, int write)
+int arc_core_mpu_buffer_validate(void *addr, size_t size, bool write)
 {
 	int r_index;
 	int key = arch_irq_lock();

arch/arm/core/aarch32/irq_manage.c

@@ -88,7 +88,7 @@ void z_arm_irq_priority_set(unsigned int irq, unsigned int prio, uint32_t flags)
 	__ASSERT(prio <= (BIT(NUM_IRQ_PRIO_BITS) - 1),
 		 "invalid priority %d for %d irq! values must be less than %lu\n",
 		 prio - _IRQ_PRIO_OFFSET, irq,
-		 BIT(NUM_IRQ_PRIO_BITS) - (_IRQ_PRIO_OFFSET));
+		 (unsigned long)BIT(NUM_IRQ_PRIO_BITS) - (_IRQ_PRIO_OFFSET));
 	NVIC_SetPriority((IRQn_Type)irq, prio);
 }
 

arch/arm/core/aarch32/mpu/arm_core_mpu.c

@@ -324,7 +324,7 @@ int arch_mem_domain_max_partitions_get(void)
 	return ARM_CORE_MPU_MAX_DOMAIN_PARTITIONS_GET(available_regions);
 }
 
-int arch_buffer_validate(void *addr, size_t size, int write)
+int arch_buffer_validate(void *addr, size_t size, bool write)
 {
 	return arm_core_mpu_buffer_validate(addr, size, write);
 }

arch/arm/core/aarch32/mpu/arm_core_mpu_dev.h

@@ -261,7 +261,7 @@ int arm_core_mpu_get_max_available_dyn_regions(void);
  *       spans multiple enabled MPU regions (even if these regions all
  *       permit user access).
  */
-int arm_core_mpu_buffer_validate(void *addr, size_t size, int write);
+int arm_core_mpu_buffer_validate(void *addr, size_t size, bool write);
 
 #endif /* CONFIG_ARM_MPU */
 

arch/arm/core/aarch32/mpu/arm_mpu.c

@@ -253,7 +253,7 @@ int arm_core_mpu_get_max_available_dyn_regions(void)
  *
  * Presumes the background mapping is NOT user accessible.
  */
-int arm_core_mpu_buffer_validate(void *addr, size_t size, int write)
+int arm_core_mpu_buffer_validate(void *addr, size_t size, bool write)
 {
 	return mpu_buffer_validate(addr, size, write);
 }

arch/arm/core/aarch32/mpu/arm_mpu_v7_internal.h

@@ -169,7 +169,7 @@ static inline int is_user_accessible_region(uint32_t r_index, int write)
  * This internal function validates whether a given memory buffer
  * is user accessible or not.
  */
-static inline int mpu_buffer_validate(void *addr, size_t size, int write)
+static inline int mpu_buffer_validate(void *addr, size_t size, bool write)
 {
 	int32_t r_index;
 	int rc = -EPERM;

arch/arm/core/aarch32/mpu/arm_mpu_v8_internal.h

@@ -270,7 +270,7 @@ static inline int is_enabled_region(uint32_t index)
  * in case the fast address range check fails.
  *
  */
-static inline int mpu_buffer_validate(void *addr, size_t size, int write)
+static inline int mpu_buffer_validate(void *addr, size_t size, bool write)
 {
 	uint32_t _addr = (uint32_t)addr;
 	uint32_t _size = (uint32_t)size;

arch/arm/core/aarch32/mpu/nxp_mpu.c

@@ -536,7 +536,7 @@ static inline int is_user_accessible_region(uint32_t r_index, int write)
 /**
  * @brief validate the given buffer is user accessible or not
  */
-int arm_core_mpu_buffer_validate(void *addr, size_t size, int write)
+int arm_core_mpu_buffer_validate(void *addr, size_t size, bool write)
 {
 	uint8_t r_index;