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>

10 files changed, 25 insertions, 44 deletions

diff --git a/drivers/gpu/drm/drm_flip_work.c b/drivers/gpu/drm/drm_flip_work.c
index e788882d9021..f9c7fa3d0012 100644
--- a/drivers/gpu/drm/drm_flip_work.c
+++ b/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);
diff --git a/drivers/iio/industrialio-event.c b/drivers/iio/industrialio-event.c
index dac15b9f9df8..c10eab64bc05 100644
--- a/drivers/iio/industrialio-event.c
+++ b/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);
         }
diff --git a/drivers/net/wireless/rt2x00/rt2800mmio.c b/drivers/net/wireless/rt2x00/rt2800mmio.c
index ae152280e071..a8cc736b5063 100644
--- a/drivers/net/wireless/rt2x00/rt2800mmio.c
+++ b/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;
                 }
diff --git a/drivers/net/wireless/rt2x00/rt2800usb.c b/drivers/net/wireless/rt2x00/rt2800usb.c
index 997df03a0c2e..a81ceb61d746 100644
--- a/drivers/net/wireless/rt2x00/rt2800usb.c
+++ b/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);
diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
index 85ca36f2136d..6b3a958e1be6 100644
--- a/drivers/pci/pcie/aer/aerdrv_core.c
+++ b/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",
diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
index 10308c6a3d1c..552d51efb429 100644
--- a/include/linux/kfifo.h
+++ b/include/linux/kfifo.h
@@ -1,7 +1,7 @@
 /*
  * 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.