Add cs42l43 PC focused SoundWire CODEC

Merge series from Charles Keepax <ckeepax@opensource.cirrus.com>:

This patch chain adds support for the Cirrus Logic cs42l43 PC focused
SoundWire CODEC.

1 files changed, 17 insertions, 1 deletions

diff --git a/fs/file.c b/fs/file.c
index 35c62b54c9d6..3fd003a8604f 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -1036,12 +1036,28 @@ unsigned long __fdget_raw(unsigned int fd)
 	return __fget_light(fd, 0);
 }
 
+/*
+ * Try to avoid f_pos locking. We only need it if the
+ * file is marked for FMODE_ATOMIC_POS, and it can be
+ * accessed multiple ways.
+ *
+ * Always do it for directories, because pidfd_getfd()
+ * can make a file accessible even if it otherwise would
+ * not be, and for directories this is a correctness
+ * issue, not a "POSIX requirement".
+ */
+static inline bool file_needs_f_pos_lock(struct file *file)
+{
+	return (file->f_mode & FMODE_ATOMIC_POS) &&
+		(file_count(file) > 1 || file->f_op->iterate_shared);
+}
+
 unsigned long __fdget_pos(unsigned int fd)
 {
 	unsigned long v = __fdget(fd);
 	struct file *file = (struct file *)(v & ~3);
 
-	if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
+	if (file && file_needs_f_pos_lock(file)) {
 		v |= FDPUT_POS_UNLOCK;
 		mutex_lock(&file->f_pos_lock);
 	}