1 files changed, 108 insertions, 0 deletions
diff --git a/kernel/drivers/memdevs.c b/kernel/drivers/memdevs.c
new file mode 100644
index 0000000..4898614
--- /dev/null
+++ b/kernel/drivers/memdevs.c
@@ -0,0 +1,108 @@
+#include "errno.h"
+#include "globals.h"
+
+#include "util/debug.h"
+#include "util/string.h"
+
+#include "mm/kmalloc.h"
+#include "mm/mobj.h"
+
+#include "drivers/chardev.h"
+
+#include "vm/anon.h"
+
+#include "fs/vnode.h"
+
+static ssize_t null_read(chardev_t *dev, size_t pos, void *buf, size_t count);
+
+static ssize_t null_write(chardev_t *dev, size_t pos, const void *buf,
+                          size_t count);
+
+static ssize_t zero_read(chardev_t *dev, size_t pos, void *buf, size_t count);
+
+static long zero_mmap(vnode_t *file, mobj_t **ret);
+
+chardev_ops_t null_dev_ops = {.read = null_read,
+                              .write = null_write,
+                              .mmap = NULL,
+                              .fill_pframe = NULL,
+                              .flush_pframe = NULL};
+
+chardev_ops_t zero_dev_ops = {.read = zero_read,
+                              .write = null_write,
+                              .mmap = zero_mmap,
+                              .fill_pframe = NULL,
+                              .flush_pframe = NULL};
+
+/**
+ * The char device code needs to know about these mem devices, so create
+ * chardev_t's for null and zero, fill them in, and register them.
+ *
+ * Use kmalloc, MEM_NULL_DEVID, MEM_ZERO_DEVID, and chardev_register.
+ * See dev.h for device ids to use with MKDEVID.
+ */
+void memdevs_init()
+{
+    NOT_YET_IMPLEMENTED("DRIVERS: ***none***");
+}
+
+/**
+ * Reads a given number of bytes from the null device into a
+ * buffer. Any read performed on the null device should read 0 bytes.
+ *
+ * @param  dev   the null device
+ * @param  pos   the offset to read from; should be ignored
+ * @param  buf   the buffer to read into
+ * @param  count the maximum number of bytes to read
+ * @return       the number of bytes read, which should be 0
+ */
+static ssize_t null_read(chardev_t *dev, size_t pos, void *buf, size_t count)
+{
+    NOT_YET_IMPLEMENTED("DRIVERS: ***none***");
+    return -ENOMEM;
+}
+
+/**
+ * Writes a given number of bytes to the null device from a
+ * buffer. Writing to the null device should _ALWAYS_ be successful
+ * and write the maximum number of bytes.
+ *
+ * @param  dev   the null device
+ * @param  pos   offset the offset to write to; should be ignored
+ * @param  buf   buffer to read from
+ * @param  count the maximum number of bytes to write
+ * @return       the number of bytes written, which should be `count`
+ */
+static ssize_t null_write(chardev_t *dev, size_t pos, const void *buf,
+                          size_t count)
+{
+    NOT_YET_IMPLEMENTED("DRIVERS: ***none***");
+    return -ENOMEM;
+}
+
+/**
+ * Reads a given number of bytes from the zero device into a
+ * buffer. Any read from the zero device should be a series of zeros.
+ *
+ * @param  dev   the zero device
+ * @param  pos   the offset to start reading from; should be ignored
+ * @param  buf   the buffer to write to
+ * @param  count the maximum number of bytes to read
+ * @return       the number of bytes read. Hint: should always read the maximum
+ *               number of bytes
+ */
+static ssize_t zero_read(chardev_t *dev, size_t pos, void *buf, size_t count)
+{
+    NOT_YET_IMPLEMENTED("DRIVERS: ***none***");
+    return 0;
+}
+
+/**
+ * Unlike in s5fs_mmap(), you can't necessarily use the file's underlying mobj.
+ * Instead, you should simply provide an anonymous object to ret.
+ */
+static long zero_mmap(vnode_t *file, mobj_t **ret)
+{
+    NOT_YET_IMPLEMENTED("VM: ***none***");
+    return -1;
+}