[SCSI] sysfs: make group is_valid return a mode_t

We have a problem in scsi_transport_spi in that we need to customise
not only the visibility of the attributes, but also their mode.  Fix
this by making the is_visible() callback return a mode, with 0
indicating is not visible.

Also add a sysfs_update_group() API to allow us to change either the
visibility or mode of the files at any time on the fly.

Acked-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index ade9a7e..dbdfabb 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -477,11 +477,10 @@
 	.poll		= sysfs_poll,
 };
 
-
-int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
-		   int type)
+int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
+			const struct attribute *attr, int type, mode_t amode)
 {
-	umode_t mode = (attr->mode & S_IALLUGO) | S_IFREG;
+	umode_t mode = (amode & S_IALLUGO) | S_IFREG;
 	struct sysfs_addrm_cxt acxt;
 	struct sysfs_dirent *sd;
 	int rc;
@@ -502,6 +501,13 @@
 }
 
 
+int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr,
+		   int type)
+{
+	return sysfs_add_file_mode(dir_sd, attr, type, attr->mode);
+}
+
+
 /**
  *	sysfs_create_file - create an attribute file for an object.
  *	@kobj:	object we're creating for.