Make read before write configurable (infrastructure part)

 - Introduce a variable in doit() that allows to influence
   read-before-write and its consequences.
 - Modify build_new_image so that it still works even if the old content
   is not read before.
 - Add copy_old_content() to ease the pain for future patches.

Corresponding to flashrom svn r1851.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>

1 files changed, 26 insertions, 5 deletions

diff --git a/layout.c b/layout.c
index a12eb28..0b9f6e5 100644
--- a/layout.c
+++ b/layout.c
@@ -257,7 +257,28 @@ int normalize_romentries(const struct flashctx *flash)
 	return ret;
 }
 
-int build_new_image(const struct flashctx *flash, uint8_t *oldcontents, uint8_t *newcontents)
+static int copy_old_content(struct flashctx *flash, int oldcontents_valid, uint8_t *oldcontents, uint8_t *newcontents, unsigned int start, unsigned int size)
+{
+	if (!oldcontents_valid) {
+		/* oldcontents is a zero-filled buffer. By reading the current data into oldcontents here, we
+		 * avoid a rewrite of identical regions even if an initial full chip read didn't happen. */
+		msg_gdbg2("Read a chunk starting at 0x%06x (len=0x%06x).\n", start, size);
+		int ret = flash->chip->read(flash, oldcontents + start, start, size);
+		if (ret != 0) {
+			msg_gerr("Failed to read chunk 0x%06x-0x%06x.\n", start, start + size - 1);
+			return 1;
+		}
+	}
+	memcpy(newcontents + start, oldcontents + start, size);
+	return 0;
+}
+
+/**
+ * Modify @newcontents so that it contains the data that should be on the chip eventually. In the case the user
+ * wants to update only parts of it, copy the chunks to be preserved from @oldcontents to @newcontents. If
+ * @oldcontents is not valid, we need to fetch the current data from the chip first.
+ */
+int build_new_image(struct flashctx *flash, bool oldcontents_valid, uint8_t *oldcontents, uint8_t *newcontents)
 {
 	unsigned int start = 0;
 	romentry_t *entry;
@@ -276,14 +297,14 @@ int build_new_image(const struct flashctx *flash, uint8_t *oldcontents, uint8_t
 		entry = get_next_included_romentry(start);
 		/* No more romentries for remaining region? */
 		if (!entry) {
-			memcpy(newcontents + start, oldcontents + start,
-			       size - start);
+			copy_old_content(flash, oldcontents_valid, oldcontents, newcontents, start,
+					 size - start);
 			break;
 		}
 		/* For non-included region, copy from old content. */
 		if (entry->start > start)
-			memcpy(newcontents + start, oldcontents + start,
-			       entry->start - start);
+			copy_old_content(flash, oldcontents_valid, oldcontents, newcontents, start,
+					 entry->start - start);
 		/* Skip to location after current romentry. */
 		start = entry->end + 1;
 		/* Catch overflow. */