kfifo: document everywhere that size has to be power of two

On my first try using them I missed that the fifos need to be power of
two, resulting in a runtime bug.  Document that requirement everywhere
(and fix one grammar bug)

Signed-off-by: Andi Kleen <[email protected]>
Acked-by: Stefani Seibold <[email protected]>
Cc: Roland Dreier <[email protected]>
Cc: Dmitry Torokhov <[email protected]>
Cc: Andy Walls <[email protected]>
Cc: Vikram Dhillon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/kfifo.h

@@ -67,7 +67,7 @@ struct kfifo {
 /**
  * DECLARE_KFIFO - macro to declare a kfifo and the associated buffer
  * @name: name of the declared kfifo datatype
- * @size: size of the fifo buffer
+ * @size: size of the fifo buffer. Must be a power of two.
  *
  * Note1: the macro can be used inside struct or union declaration
  * Note2: the macro creates two objects:
@@ -91,7 +91,7 @@ union { \
 /**
  * DEFINE_KFIFO - macro to define and initialize a kfifo
  * @name: name of the declared kfifo datatype
- * @size: size of the fifo buffer
+ * @size: size of the fifo buffer. Must be a power of two.
  *
  * Note1: the macro can be used for global and local kfifo data type variables
  * Note2: the macro creates two objects:

kernel/kfifo.c

@@ -41,7 +41,7 @@ static void _kfifo_init(struct kfifo *fifo, void *buffer,
  * kfifo_init - initialize a FIFO using a preallocated buffer
  * @fifo: the fifo to assign the buffer
  * @buffer: the preallocated buffer to be used.
- * @size: the size of the internal buffer, this have to be a power of 2.
+ * @size: the size of the internal buffer, this has to be a power of 2.
  *
  */
 void kfifo_init(struct kfifo *fifo, void *buffer, unsigned int size)