From: Christoph Hellwig <hch@lst.de>
Date: Thu, 21 Nov 2002 04:24:43 +0000 (-0800)
Subject: [PATCH] uClinux bits for /dev/zero
X-Git-Tag: v2.5.49~6^2~3
X-Git-Url: http://git.neil.brown.name/?a=commitdiff_plain;h=d04e13f07b945e4f2ff99f1e721964b266df602d;p=history.git

[PATCH] uClinux bits for /dev/zero

uClinux ports can't use mmu tricks for reading /dev/zero due to the
lack of one.  similarly it can't mmap /dev/zero.
---

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 129bce3a0d73..c1ca48f798e0 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -377,6 +377,7 @@ static ssize_t write_null(struct file * file, const char * buf,
 	return count;
 }
 
+#ifdef CONFIG_MMU
 /*
  * For fun, we are using the MMU for this.
  */
@@ -476,6 +477,29 @@ static int mmap_zero(struct file * file, struct vm_area_struct * vma)
 		return -EAGAIN;
 	return 0;
 }
+#else /* CONFIG_MMU */
+static ssize_t read_zero(struct file * file, char * buf, 
+			 size_t count, loff_t *ppos)
+{
+	unsigned long left;
+
+	if (!count)
+		return 0;
+
+	for (left = count; left > 0; left--, buf++) {
+		if (put_user(0, buf))
+			return -EFAULT;
+		cond_resched();
+	}
+
+	return count;
+}
+
+static int mmap_zero(struct file * file, struct vm_area_struct * vma)
+{
+	return -ENOSYS;
+}
+#endif /* CONFIG_MMU */
 
 static ssize_t write_full(struct file * file, const char * buf,
 			  size_t count, loff_t *ppos)