kern: vfs: Add vnode operation for reads

Introduces a read callback wrapper implementation for vnodes to simplify
file reading

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 42 insertions, 0 deletions

diff --git a/src/sys/include/os/vnode.h b/src/sys/include/os/vnode.h
index 77459a1..868e137 100644
--- a/src/sys/include/os/vnode.h
+++ b/src/sys/include/os/vnode.h
@@ -87,6 +87,7 @@ struct vop_rw_data {
 struct vop {
     int(*lookup)(struct vop_lookup_args *args);
     ssize_t(*write)(struct vop_rw_data *data);
+    ssize_t(*read)(struct vop_rw_data *data);
 };
 
 /*
@@ -147,4 +148,16 @@ int vfs_vrel(struct vnode *vp, int flags);
  */
 ssize_t vop_write(struct vnode *vp, char *data, size_t len);
 
+/*
+ * Wrapper for the read write callback
+ *
+ * @vp: Vnode to read from
+ * @data: Read data written here
+ * @len: Length of bytes to read
+ *
+ * Returns the number of bytes read on success, otherwise
+ * a less than zero value on failure.
+ */
+ssize_t vop_read(struct vnode *vp, char *data, size_t len);
+
 #endif  /* !_OS_VNODE_H_ */
diff --git a/src/sys/os/vfs_subr.c b/src/sys/os/vfs_subr.c
index 8d5b032..47ed468 100644
--- a/src/sys/os/vfs_subr.c
+++ b/src/sys/os/vfs_subr.c
@@ -172,3 +172,32 @@ vop_write(struct vnode *vp, char *data, size_t len)
     rwdata.vp = vp;
     return vops->write(&rwdata);
 }
+
+ssize_t
+vop_read(struct vnode *vp, char *data, size_t len)
+{
+    struct vop_rw_data rwdata;
+    struct vop *vops;
+
+    if (vp == NULL || data == NULL) {
+        return -EINVAL;
+    }
+
+    if (len == 0) {
+        return -EINVAL;
+    }
+
+    /* Grab the virtual operations */
+    if ((vops = vp->vops) == NULL) {
+        return -EIO;
+    }
+
+    if (vops->read == NULL) {
+        return -ENOTSUP;
+    }
+
+    rwdata.data = data;
+    rwdata.len = len;
+    rwdata.vp = vp;
+    return vops->read(&rwdata);
+}