From: H. Peter Anvin <hpa@linux.intel.com>
Date: Mon, 28 Jun 2010 21:34:08 +0000 (-0700)
Subject: diskio: hard-code CD-ROM sectors to 2048 bytes
X-Git-Tag: syslinux-4.00~2
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=c126c28095caf13d164b21f4c7cb25a44af859b0;p=platform%2Fupstream%2Fsyslinux.git

diskio: hard-code CD-ROM sectors to 2048 bytes

At least the ThinkPad T22 and T23 will incorrectly report a sector
size of 512 bytes for El Torito CD-ROMs.  Ignore the reported sector
size for El Torito boots.

Reported-by: Helmut Hullen <hullen@t-online.de>
Tested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---

diff --git a/core/fs/diskio.c b/core/fs/diskio.c
index b832868..1625bdb 100644
--- a/core/fs/diskio.c
+++ b/core/fs/diskio.c
@@ -278,7 +278,18 @@ struct disk *disk_init(uint8_t devno, bool cdrom, sector_t part_start,
 	    if (edd_params.len < sizeof edd_params)
 		memset((char *)&edd_params + edd_params.len, 0,
 		       sizeof edd_params - edd_params.len);
-	    if (edd_params.sector_size >= 512 &&
+
+	    /*
+	     * Note: filter impossible sector sizes.  Some BIOSes
+	     * are known to report incorrect sector size information
+	     * (usually 512 rather than 2048) for CD-ROMs, so at least
+	     * for now ignore the reported sector size if booted via
+	     * El Torito.
+	     *
+	     * Known affected systems: ThinkPad T22, T23.
+	     */
+	    if (!cdrom &&
+		edd_params.sector_size >= 512 &&
 		is_power_of_2(edd_params.sector_size))
 		sector_size = edd_params.sector_size;
 	}