We have to restrict the maximum length to less than 0xff. However,
according to Kurt Garloff:

Also, you probably send a 6 byte command, max alloc length would be 255, 
and we'd better round that down to 254 then. (Uneven counts on wide SCSI 
busses are a bit nasty and tend to trigger bugs in the LLDs w.r.t. handling 
of the IGNORE_RESIDUAL msg.) 

So we'll be using 254 throughout.

Index: udev-021/extras/scsi_id/scsi_serial.c
===================================================================
--- udev-021.orig/extras/scsi_id/scsi_serial.c	2004-03-03 01:01:32.000000000 +0100
+++ udev-021/extras/scsi_id/scsi_serial.c	2004-06-24 17:03:16.000000000 +0200
@@ -303,7 +303,7 @@ static int scsi_inquiry(struct sysfs_dev
 	unsigned char *buffer;
 	int retry = 3; /* rather random */
 
-	if (buflen > 255) {
+	if (buflen > 254) {
 		log_message(LOG_WARNING, "buflen %d too long\n", buflen);
 		return -1;
 	}
@@ -356,6 +356,7 @@ resend:
 	return retval;
 }
 
+/* Get list of supported EVPD pages */
 static int do_scsi_page0_inquiry(struct sysfs_device *scsi_dev, int fd,
 				 char *buffer, int len)
 {
@@ -544,6 +561,7 @@ static int check_fill_0x83_id(struct sys
 	return 0;
 }
 
+/* Get device identification VPD page */
 static int do_scsi_page83_inquiry(struct sysfs_device *scsi_dev, int fd,
 				  char *serial, int len)
 {
@@ -552,7 +570,7 @@ static int do_scsi_page83_inquiry(struct
 	unsigned char page_83[256];
 
 	memset(page_83, 0, 256);
-	retval = scsi_inquiry(scsi_dev, fd, 1, 0x83, page_83, 255);
+	retval = scsi_inquiry(scsi_dev, fd, 1, 0x83, page_83, 254);
 	if (retval < 0)
 		return 1;
 
@@ -601,6 +619,7 @@ static int do_scsi_page83_inquiry(struct
 	return 1;
 }
 
+/* Get unit serial number VPD page */
 static int do_scsi_page80_inquiry(struct sysfs_device *scsi_dev, int fd,
 				  char *serial, int max_len)
 {
@@ -611,7 +630,7 @@ static int do_scsi_page80_inquiry(struct
 	unsigned char buf[256];
 
 	memset(buf, 0, 256);
-	retval = scsi_inquiry(scsi_dev, fd, 1, 0x80, buf, 255);
+	retval = scsi_inquiry(scsi_dev, fd, 1, 0x80, buf, 254);
 	if (retval < 0)
 		return retval;
 
@@ -649,7 +668,8 @@ int scsi_get_serial (struct sysfs_device
 	int ind;
 	int retval;
 
-	if (len > 255) {
+	if (len > 254) {
+		len = 254;
 	}
 	memset(serial, 0, len);
 	dprintf("opening %s\n", devname);
@@ -686,7 +706,7 @@ int scsi_get_serial (struct sysfs_device
 	 * Get page 0, the page of the pages. By default, try from best to
 	 * worst of supported pages: 0x83 then 0x80.
 	 */
-	if (do_scsi_page0_inquiry(scsi_dev, fd, page0, 255)) {
+	if (do_scsi_page0_inquiry(scsi_dev, fd, page0, 254)) {
 		/*
 		 * Don't try anything else. Black list if a specific page
 		 * should be used for this vendor+model, or maybe have an