kfifo API type safety

This patch enhances the type safety for the kfifo API.  It is now safe
to put const data into a non const FIFO and the API will now generate a
compiler warning when reading from the fifo where the destination
address is pointing to a const variable.

As a side effect the kfifo_put() does now expect the value of an element
instead a pointer to the element.  This was suggested Russell King.  It
make the handling of the kfifo_put easier since there is no need to
create a helper variable for getting the address of a pointer or to pass
integers of different sizes.

IMHO the API break is okay, since there are currently only six users of
kfifo_put().

The code is also cleaner by kicking out the "if (0)" expressions.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Stefani Seibold <stefani@seibold.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/gpu/drm/drm_flip_work.c

@@ -34,7 +34,7 @@
  */
 void drm_flip_work_queue(struct drm_flip_work *work, void *val)
 {
-	if (kfifo_put(&work->fifo, (const void **)&val)) {
+	if (kfifo_put(&work->fifo, val)) {
 		atomic_inc(&work->pending);
 	} else {
 		DRM_ERROR("%s fifo full!\n", work->name);

drivers/iio/industrialio-event.c

@@ -56,7 +56,7 @@ int iio_push_event(struct iio_dev *indio_dev, u64 ev_code, s64 timestamp)
 		ev.id = ev_code;
 		ev.timestamp = timestamp;
 
-		copied = kfifo_put(&ev_int->det_events, &ev);
+		copied = kfifo_put(&ev_int->det_events, ev);
 		if (copied != 0)
 			wake_up_locked_poll(&ev_int->wait, POLLIN);
 	}

drivers/net/wireless/rt2x00/rt2800mmio.c

@@ -446,7 +446,7 @@ static void rt2800mmio_txstatus_interrupt(struct rt2x00_dev *rt2x00dev)
 		if (!rt2x00_get_field32(status, TX_STA_FIFO_VALID))
 			break;
 
-		if (!kfifo_put(&rt2x00dev->txstatus_fifo, &status)) {
+		if (!kfifo_put(&rt2x00dev->txstatus_fifo, status)) {
 			rt2x00_warn(rt2x00dev, "TX status FIFO overrun, drop tx status report\n");
 			break;
 		}

drivers/net/wireless/rt2x00/rt2800usb.c

@@ -164,7 +164,7 @@ static bool rt2800usb_tx_sta_fifo_read_completed(struct rt2x00_dev *rt2x00dev,
 
 	valid = rt2x00_get_field32(tx_status, TX_STA_FIFO_VALID);
 	if (valid) {
-		if (!kfifo_put(&rt2x00dev->txstatus_fifo, &tx_status))
+		if (!kfifo_put(&rt2x00dev->txstatus_fifo, tx_status))
 			rt2x00_warn(rt2x00dev, "TX status FIFO overrun\n");
 
 		queue_work(rt2x00dev->workqueue, &rt2x00dev->txdone_work);

drivers/pci/pcie/aer/aerdrv_core.c

@@ -574,7 +574,7 @@ void aer_recover_queue(int domain, unsigned int bus, unsigned int devfn,
 	};
 
 	spin_lock_irqsave(&aer_recover_ring_lock, flags);
-	if (kfifo_put(&aer_recover_ring, &entry))
+	if (kfifo_put(&aer_recover_ring, entry))
 		schedule_work(&aer_recover_work);
 	else
 		pr_err("AER recover: Buffer overflow when recovering AER for %04x:%02x:%02x:%x\n",

include/linux/kfifo.h

 /*
  * A generic kernel FIFO implementation
  *
- * Copyright (C) 2009/2010 Stefani Seibold <stefani@seibold.net>
+ * Copyright (C) 2013 Stefani Seibold <stefani@seibold.net>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -67,9 +67,10 @@ struct __kfifo {
 	union { \
 		struct __kfifo	kfifo; \
 		datatype	*type; \
+		const datatype	*const_type; \
 		char		(*rectype)[recsize]; \
 		ptrtype		*ptr; \
-		const ptrtype	*ptr_const; \
+		ptrtype const	*ptr_const; \
 	}
 
 #define __STRUCT_KFIFO(type, size, recsize, ptrtype) \
@@ -386,16 +387,12 @@ __kfifo_int_must_check_helper( \
 #define	kfifo_put(fifo, val) \
 ({ \
 	typeof((fifo) + 1) __tmp = (fifo); \
-	typeof((val) + 1) __val = (val); \
+	typeof(*__tmp->const_type) __val = (val); \
 	unsigned int __ret; \
-	const size_t __recsize = sizeof(*__tmp->rectype); \
+	size_t __recsize = sizeof(*__tmp->rectype); \
 	struct __kfifo *__kfifo = &__tmp->kfifo; \
-	if (0) { \
-		typeof(__tmp->ptr_const) __dummy __attribute__ ((unused)); \
-		__dummy = (typeof(__val))NULL; \
-	} \
 	if (__recsize) \
-		__ret = __kfifo_in_r(__kfifo, __val, sizeof(*__val), \
+		__ret = __kfifo_in_r(__kfifo, &__val, sizeof(__val), \
 			__recsize); \
 	else { \
 		__ret = !kfifo_is_full(__tmp); \
@@ -404,7 +401,7 @@ __kfifo_int_must_check_helper( \
 			((typeof(__tmp->type))__kfifo->data) : \
 			(__tmp->buf) \
 			)[__kfifo->in & __tmp->kfifo.mask] = \
-				*(typeof(__tmp->type))__val; \
+				(typeof(*__tmp->type))__val; \
 			smp_wmb(); \
 			__kfifo->in++; \
 		} \
@@ -415,7 +412,7 @@ __kfifo_int_must_check_helper( \
 /**
  * kfifo_get - get data from the fifo
  * @fifo: address of the fifo to be used
- * @val: the var where to store the data to be added
+ * @val: address where to store the data
  *
  * This macro reads the data from the fifo.
  * It returns 0 if the fifo was empty. Otherwise it returns the number
@@ -428,12 +425,10 @@ __kfifo_int_must_check_helper( \
 __kfifo_uint_must_check_helper( \
 ({ \
 	typeof((fifo) + 1) __tmp = (fifo); \
-	typeof((val) + 1) __val = (val); \
+	typeof(__tmp->ptr) __val = (val); \
 	unsigned int __ret; \
 	const size_t __recsize = sizeof(*__tmp->rectype); \
 	struct __kfifo *__kfifo = &__tmp->kfifo; \
-	if (0) \
-		__val = (typeof(__tmp->ptr))0; \
 	if (__recsize) \
 		__ret = __kfifo_out_r(__kfifo, __val, sizeof(*__val), \
 			__recsize); \
@@ -456,7 +451,7 @@ __kfifo_uint_must_check_helper( \
 /**
  * kfifo_peek - get data from the fifo without removing
  * @fifo: address of the fifo to be used
- * @val: the var where to store the data to be added
+ * @val: address where to store the data
  *
  * This reads the data from the fifo without removing it from the fifo.
  * It returns 0 if the fifo was empty. Otherwise it returns the number
@@ -469,12 +464,10 @@ __kfifo_uint_must_check_helper( \
 __kfifo_uint_must_check_helper( \
 ({ \
 	typeof((fifo) + 1) __tmp = (fifo); \
-	typeof((val) + 1) __val = (val); \
+	typeof(__tmp->ptr) __val = (val); \
 	unsigned int __ret; \
 	const size_t __recsize = sizeof(*__tmp->rectype); \
 	struct __kfifo *__kfifo = &__tmp->kfifo; \
-	if (0) \
-		__val = (typeof(__tmp->ptr))NULL; \
 	if (__recsize) \
 		__ret = __kfifo_out_peek_r(__kfifo, __val, sizeof(*__val), \
 			__recsize); \
@@ -508,14 +501,10 @@ __kfifo_uint_must_check_helper( \
 #define	kfifo_in(fifo, buf, n) \
 ({ \
 	typeof((fifo) + 1) __tmp = (fifo); \
-	typeof((buf) + 1) __buf = (buf); \
+	typeof(__tmp->ptr_const) __buf = (buf); \
 	unsigned long __n = (n); \
 	const size_t __recsize = sizeof(*__tmp->rectype); \
 	struct __kfifo *__kfifo = &__tmp->kfifo; \
-	if (0) { \
-		typeof(__tmp->ptr_const) __dummy __attribute__ ((unused)); \
-		__dummy = (typeof(__buf))NULL; \
-	} \
 	(__recsize) ?\
 	__kfifo_in_r(__kfifo, __buf, __n, __recsize) : \
 	__kfifo_in(__kfifo, __buf, __n); \
@@ -561,14 +550,10 @@ __kfifo_uint_must_check_helper( \
 __kfifo_uint_must_check_helper( \
 ({ \
 	typeof((fifo) + 1) __tmp = (fifo); \
-	typeof((buf) + 1) __buf = (buf); \
+	typeof(__tmp->ptr) __buf = (buf); \
 	unsigned long __n = (n); \
 	const size_t __recsize = sizeof(*__tmp->rectype); \
 	struct __kfifo *__kfifo = &__tmp->kfifo; \
-	if (0) { \
-		typeof(__tmp->ptr) __dummy = NULL; \
-		__buf = __dummy; \
-	} \
 	(__recsize) ?\
 	__kfifo_out_r(__kfifo, __buf, __n, __recsize) : \
 	__kfifo_out(__kfifo, __buf, __n); \
@@ -773,14 +758,10 @@ __kfifo_uint_must_check_helper( \
 __kfifo_uint_must_check_helper( \
 ({ \
 	typeof((fifo) + 1) __tmp = (fifo); \
-	typeof((buf) + 1) __buf = (buf); \
+	typeof(__tmp->ptr) __buf = (buf); \
 	unsigned long __n = (n); \
 	const size_t __recsize = sizeof(*__tmp->rectype); \
 	struct __kfifo *__kfifo = &__tmp->kfifo; \
-	if (0) { \
-		typeof(__tmp->ptr) __dummy __attribute__ ((unused)) = NULL; \
-		__buf = __dummy; \
-	} \
 	(__recsize) ? \
 	__kfifo_out_peek_r(__kfifo, __buf, __n, __recsize) : \
 	__kfifo_out_peek(__kfifo, __buf, __n); \

mm/memory-failure.c

@@ -1269,7 +1269,7 @@ void memory_failure_queue(unsigned long pfn, int trapno, int flags)
 
 	mf_cpu = &get_cpu_var(memory_failure_cpu);
 	spin_lock_irqsave(&mf_cpu->lock, proc_flags);
-	if (kfifo_put(&mf_cpu->fifo, &entry))
+	if (kfifo_put(&mf_cpu->fifo, entry))
 		schedule_work_on(smp_processor_id(), &mf_cpu->work);
 	else
 		pr_err("Memory failure: buffer overflow when queuing memory failure at %#lx\n",

samples/kfifo/bytestream-example.c

@@ -64,7 +64,7 @@ static int __init testfunc(void)
 
 	/* put values into the fifo */
 	for (i = 0; i != 10; i++)
-		kfifo_put(&test, &i);
+		kfifo_put(&test, i);
 
 	/* show the number of used elements */
 	printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
@@ -85,7 +85,7 @@ static int __init testfunc(void)
 	kfifo_skip(&test);
 
 	/* put values into the fifo until is full */
-	for (i = 20; kfifo_put(&test, &i); i++)
+	for (i = 20; kfifo_put(&test, i); i++)
 		;
 
 	printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));

samples/kfifo/dma-example.c

@@ -39,7 +39,7 @@ static int __init example_init(void)
 	kfifo_in(&fifo, "test", 4);
 
 	for (i = 0; i != 9; i++)
-		kfifo_put(&fifo, &i);
+		kfifo_put(&fifo, i);
 
 	/* kick away first byte */
 	kfifo_skip(&fifo);

samples/kfifo/inttype-example.c

@@ -61,7 +61,7 @@ static int __init testfunc(void)
 
 	/* put values into the fifo */
 	for (i = 0; i != 10; i++)
-		kfifo_put(&test, &i);
+		kfifo_put(&test, i);
 
 	/* show the number of used elements */
 	printk(KERN_INFO "fifo len: %u\n", kfifo_len(&test));
@@ -78,7 +78,7 @@ static int __init testfunc(void)
 	kfifo_skip(&test);
 
 	/* put values into the fifo until is full */
-	for (i = 20; kfifo_put(&test, &i); i++)
+	for (i = 20; kfifo_put(&test, i); i++)
 		;
 
 	printk(KERN_INFO "queue len: %u\n", kfifo_len(&test));