kfifo: add kfifo_skip, kfifo_from_user and kfifo_to_user

Add kfifo_reset_out() for save lockless discard the fifo output
 Add kfifo_skip() to skip a number of output bytes
 Add kfifo_from_user() to copy user space data into the fifo
 Add kfifo_to_user() to copy fifo data to user space

Signed-off-by: Stefani Seibold <stefani@seibold.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 47 insertions, 0 deletions

diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
index dd53eed3e2af..d3230fb08bc7 100644
--- a/include/linux/kfifo.h
+++ b/include/linux/kfifo.h
@@ -125,6 +125,16 @@ static inline void kfifo_reset(struct kfifo *fifo)
 }
 
 /**
+ * kfifo_reset_out - skip FIFO contents
+ * @fifo: the fifo to be emptied.
+ */
+static inline void kfifo_reset_out(struct kfifo *fifo)
+{
+	smp_mb();
+	fifo->out = fifo->in;
+}
+
+/**
  * kfifo_size - returns the size of the fifo in bytes
  * @fifo: the fifo to be used.
  */
@@ -231,4 +241,41 @@ static inline __must_check unsigned int kfifo_out_locked(struct kfifo *fifo,
 	return ret;
 }
 
+extern void kfifo_skip(struct kfifo *fifo, unsigned int len);
+
+extern __must_check unsigned int kfifo_from_user(struct kfifo *fifo,
+	const void __user *from, unsigned int n);
+
+extern __must_check unsigned int kfifo_to_user(struct kfifo *fifo,
+	void __user *to, unsigned int n);
+
+/**
+ * __kfifo_add_out internal helper function for updating the out offset
+ */
+static inline void __kfifo_add_out(struct kfifo *fifo,
+				unsigned int off)
+{
+	smp_mb();
+	fifo->out += off;
+}
+
+/**
+ * __kfifo_add_in internal helper function for updating the in offset
+ */
+static inline void __kfifo_add_in(struct kfifo *fifo,
+				unsigned int off)
+{
+	smp_wmb();
+	fifo->in += off;
+}
+
+/**
+ * __kfifo_off internal helper function for calculating the index of a
+ * given offeset
+ */
+static inline unsigned int __kfifo_off(struct kfifo *fifo, unsigned int off)
+{
+	return off & (fifo->size - 1);
+}
+
 #endif