From 8c2e0ce946012a4275e8dfa9d8dfd1d5a68d6e3e Mon Sep 17 00:00:00 2001
From: sotech117 <michael_foiani@brown.edu>
Date: Sat, 2 Mar 2024 23:05:26 +0000
Subject: decent coding session

---
 kernel/drivers/memdevs.c | 60 ++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 53 insertions(+), 7 deletions(-)

(limited to 'kernel/drivers/memdevs.c')

diff --git a/kernel/drivers/memdevs.c b/kernel/drivers/memdevs.c
index 50815d3..815143a 100644
--- a/kernel/drivers/memdevs.c
+++ b/kernel/drivers/memdevs.c
@@ -43,7 +43,31 @@ chardev_ops_t zero_dev_ops = {.read = zero_read,
  */
 void memdevs_init()
 {
-    NOT_YET_IMPLEMENTED("DRIVERS: memdevs_init");
+    // NOT_YET_IMPLEMENTED("DRIVERS: memdevs_init");
+
+    // create chardev_t's for null and zero
+    chardev_t *null_dev = kmalloc(sizeof(chardev_t));
+    if (null_dev == NULL)
+    {
+        dbg(DBG_DISK, "ERROR: kmalloc failed on null_dev in memdevs_init\n");
+        return;
+    }
+    chardev_t *zero_dev = kmalloc(sizeof(chardev_t));
+    if (zero_dev == NULL)
+    {
+        dbg(DBG_DISK, "ERROR: kmalloc failed on zero_dev in memdevs_init\n");
+        return;
+    }
+
+    // fill them in
+    null_dev->cd_id = MEM_NULL_DEVID;
+    null_dev->cd_ops = &null_dev_ops;
+    zero_dev->cd_id = MEM_ZERO_DEVID;
+    zero_dev->cd_ops = &zero_dev_ops;
+
+    // register them
+    chardev_register(null_dev);
+    chardev_register(zero_dev);
 }
 
 /**
@@ -58,8 +82,9 @@ void memdevs_init()
  */
 static ssize_t null_read(chardev_t *dev, size_t pos, void *buf, size_t count)
 {
-    NOT_YET_IMPLEMENTED("DRIVERS: null_read");
-    return -ENOMEM;
+    // NOT_YET_IMPLEMENTED("DRIVERS: null_read");
+    // TODO: ask about buffer checking
+    return 0; // return reading no bytes
 }
 
 /**
@@ -76,8 +101,18 @@ 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)
 {
-    NOT_YET_IMPLEMENTED("DRIVERS: null_write");
-    return -ENOMEM;
+    // NOT_YET_IMPLEMENTED("DRIVERS: null_write");
+
+    // check if the buffer is NULL
+    if (buf == NULL)
+    {
+        return -EINVAL;
+    }
+
+    // there is no true writing, so just do nothing here
+
+    // return the number of bytes written
+    return count;
 }
 
 /**
@@ -93,8 +128,19 @@ static ssize_t null_write(chardev_t *dev, size_t pos, const void *buf,
  */
 static ssize_t zero_read(chardev_t *dev, size_t pos, void *buf, size_t count)
 {
-    NOT_YET_IMPLEMENTED("DRIVERS: zero_read");
-    return 0;
+    // NOT_YET_IMPLEMENTED("DRIVERS: zero_read");
+
+    // check if the buffer is NULL
+    if (buf == NULL)
+    {
+        return -EINVAL;
+    }
+
+    // fill the buffer with zeros
+    memset(buf, 0, count);
+
+    // return the number of bytes read
+    return count;
 }
 
 /**
-- 
cgit v1.2.3-70-g09d2