From 662e0238f062b838361bca91d465813da710acd4 Mon Sep 17 00:00:00 2001
From: Dave Wysochanski <dwysocha@redhat.com>
Date: Thu, 19 Apr 2007 02:10:42 +0000
Subject: [PATCH] Add dev_read_circular, read 2 regions on same device.

---
 WHATS_NEW           |  1 +
 lib/config/config.c | 12 ++----------
 lib/device/dev-io.c | 29 +++++++++++++++++++++++++++++
 lib/device/device.h |  2 ++
 4 files changed, 34 insertions(+), 10 deletions(-)

diff --git a/WHATS_NEW b/WHATS_NEW
index 9abfa4790..cc6d9b74e 100644
--- a/WHATS_NEW
+++ b/WHATS_NEW
@@ -1,5 +1,6 @@
 Version 2.02.25 -
 =================================
+  Add dev_read_circular.
   Add pvck command stub.
   Update lists of attribute characters in man pages.
   Change cling alloc policy attribute character from 'C' to l'.
diff --git a/lib/config/config.c b/lib/config/config.c
index 159e74106..6c7128a41 100644
--- a/lib/config/config.c
+++ b/lib/config/config.c
@@ -210,18 +210,10 @@ int read_config_fd(struct config_tree *cft, struct device *dev,
 			stack;
 			return 0;
 		}
-		if (!dev_read(dev, (uint64_t) offset, size, buf)) {
-			log_error("Read from %s failed", dev_name(dev));
+		if (!dev_read_circular(dev, (uint64_t) offset, size,
+				       (uint64_t) offset2, size2, buf)) {
 			goto out;
 		}
-		if (size2) {
-			if (!dev_read(dev, (uint64_t) offset2, size2,
-				      buf + size)) {
-				log_error("Circular read from %s failed",
-					  dev_name(dev));
-				goto out;
-			}
-		}
 		p->fb = buf;
 	}
 
diff --git a/lib/device/dev-io.c b/lib/device/dev-io.c
index 8e8582e04..0e50e5110 100644
--- a/lib/device/dev-io.c
+++ b/lib/device/dev-io.c
@@ -564,6 +564,35 @@ int dev_read(struct device *dev, uint64_t offset, size_t len, void *buffer)
 	return _aligned_io(&where, buffer, 0);
 }
 
+/*
+ * Read from 'dev' into 'buf', possibly in 2 distinct regions, denoted
+ * by (offset,len) and (offset2,len2).  Thus, the total size of
+ * 'buf' should be len+len2.
+ */
+int dev_read_circular(struct device *dev, uint64_t offset, size_t len,
+		      uint64_t offset2, size_t len2, void *buf)
+{
+	if (!dev_read(dev, offset, len, buf)) {
+		log_error("Read from %s failed", dev_name(dev));
+		return 0;
+	}
+
+	/*
+	 * The second region is optional, and allows for
+	 * a circular buffer on the device.
+	 */
+	if (!len2)
+		return 1;
+
+	if (!dev_read(dev, offset2, len2, buf + len)) {
+		log_error("Circular read from %s failed",
+			  dev_name(dev));
+		return 0;
+	}
+
+	return 1;
+}
+
 /* FIXME If O_DIRECT can't extend file, dev_extend first; dev_truncate after.
  *       But fails if concurrent processes writing
  */
diff --git a/lib/device/device.h b/lib/device/device.h
index 4dc08e64d..19a9e1764 100644
--- a/lib/device/device.h
+++ b/lib/device/device.h
@@ -78,6 +78,8 @@ int dev_fd(struct device *dev);
 const char *dev_name(const struct device *dev);
 
 int dev_read(struct device *dev, uint64_t offset, size_t len, void *buffer);
+int dev_read_circular(struct device *dev, uint64_t offset, size_t len,
+		      uint64_t offset2, size_t len2, void *buf);
 int dev_write(struct device *dev, uint64_t offset, size_t len, void *buffer);
 int dev_append(struct device *dev, size_t len, void *buffer);
 int dev_set(struct device *dev, uint64_t offset, size_t len, int value);
-- 
2.43.5