[syslinux:pathbased] diskio: sanitize the reduced transfer sizes

[syslinux-bot for H. Peter Anvin]

Commit-ID:  edd10c1dc8a724aa113a0af88cf5c04a8fe2155f
Gitweb:     http://syslinux.zytor.com/commit/edd10c1dc8a724aa113a0af88cf5c04a8fe2155f
Author:     H. Peter Anvin <hpa at linux.intel.com>
AuthorDate: Wed, 12 May 2010 17:28:51 -0700
Committer:  H. Peter Anvin <hpa at linux.intel.com>
CommitDate: Wed, 12 May 2010 17:28:51 -0700

diskio: sanitize the reduced transfer sizes

Simply shift the size left by 1 when computing the transfer sizes.
This will always end with the values ..., 1, 0 as it should.

Signed-off-by: H. Peter Anvin <hpa at linux.intel.com>


---
 core/fs/diskio.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/core/fs/diskio.c b/core/fs/diskio.c
index 6afba21..cdbed79 100644
--- a/core/fs/diskio.c
+++ b/core/fs/diskio.c
@@ -74,8 +74,8 @@ static int chs_rdwr_sectors(struct disk *disk, void *buf,
 	    if (retry--)
 		continue;
 
-            /* if we are reading ONE sector and go here, just make it _faile_ */
-            chunk = chunk == 1 ? 0 : ((chunk+1) >> 1);
+	    /* For any starting value, this will always end with ..., 1, 0 */
+	    chunk >>= 1;
             if (chunk) {
 		MaxTransfer = chunk;
 		retry = RETRY_COUNT;
@@ -163,13 +163,16 @@ static int edd_rdwr_sectors(struct disk *disk, void *buf,
 		break;
 	    if (retry--)
 		continue;
-	    chunk = chunk == 1 ? 0 : ((chunk+1) >> 1);
+
+	    /* For any starting value, this will always end with ..., 1, 0 */
+	    chunk >>= 1;
 	    if (chunk) {
 		MaxTransfer = chunk;
 		retry = RETRY_COUNT;
                 pkt.blocks = chunk;
 		continue;
 	    }
+
 	    /*** XXX: Consider falling back to CHS here?! ***/
             printf("reading sectors error(EDD)\n");
 	    return done;	/* Failure */