Calculate checksum when writing EEPROM or alias address.
--- a/NEWS Wed Sep 19 09:07:36 2007 +0000
+++ b/NEWS Wed Sep 19 09:37:01 2007 +0000
@@ -6,6 +6,7 @@
Changes in version 1.3.2:
+* Calculate checksum when writing EEPROM or alias address.
* Removed config.kbuild and replaced Kbuild files by Kbuild.in files.
-------------------------------------------------------------------------------
--- a/master/slave.c Wed Sep 19 09:07:36 2007 +0000
+++ b/master/slave.c Wed Sep 19 09:37:01 2007 +0000
@@ -891,6 +891,46 @@
/*****************************************************************************/
/**
+ * Calculates the EEPROM checksum field.
+ *
+ * The checksum is generated with the polynom x^8+x^2+x+1 (0x07) and an
+ * initial value of 0xff (see IEC 61158-6-12 ch. 5.4).
+ *
+ * The below code was originally generated with PYCRC
+ * http://www.tty1.net/pycrc
+ *
+ * ./pycrc.py --width=8 --poly=0x07 --reflect-in=0 --xor-in=0xff
+ * --reflect-out=0 --xor-out=0 --generate c --algorithm=bit-by-bit
+ *
+ * \return CRC8
+ */
+
+uint8_t ec_slave_eeprom_crc(const uint8_t *data, size_t length)
+{
+ unsigned int i;
+ uint8_t bit, byte, crc = 0x48;
+
+ while (length--) {
+ byte = *data++;
+ for (i = 0; i < 8; i++) {
+ bit = crc & 0x80;
+ crc = (crc << 1) | ((byte >> (7 - i)) & 0x01);
+ if (bit) crc ^= 0x07;
+ }
+ }
+
+ for (i = 0; i < 8; i++) {
+ bit = crc & 0x80;
+ crc <<= 1;
+ if (bit) crc ^= 0x07;
+ }
+
+ return crc;
+}
+
+/*****************************************************************************/
+
+/**
* Writes complete EEPROM contents to a slave.
* \return data size written in case of success, otherwise error code.
*/
@@ -904,6 +944,7 @@
const uint16_t *cat_header;
uint16_t cat_type, cat_size;
int ret;
+ uint8_t crc;
if (slave->master->mode != EC_MASTER_MODE_IDLE) { // FIXME
EC_ERR("Writing EEPROMs only allowed in idle mode!\n");
@@ -927,6 +968,12 @@
return -EINVAL;
}
+ // calculate checksum
+ crc = ec_slave_eeprom_crc(data, 14); // CRC over words 0 to 6
+ if (crc != data[14]) {
+ EC_WARN("EEPROM CRC incorrect. Must be 0x%02x.\n", crc);
+ }
+
cat_header = request.words + EC_FIRST_EEPROM_CATEGORY_OFFSET;
cat_type = EC_READ_U16(cat_header);
while (cat_type != 0xFFFF) { // cycle through categories
@@ -964,11 +1011,12 @@
{
ec_eeprom_write_request_t request;
char *remainder;
- uint16_t alias, word;
+ uint16_t alias, words[8];
int ret;
+ uint8_t crc;
if (slave->master->mode != EC_MASTER_MODE_IDLE) { // FIXME
- EC_ERR("Writing EEPROMs only allowed in idle mode!\n");
+ EC_ERR("Writing to EEPROM is only allowed in idle mode!\n");
return -EBUSY;
}
@@ -977,16 +1025,29 @@
EC_ERR("Invalid alias value! Dropping.\n");
return -EINVAL;
}
+
+ if (!slave->eeprom_data || slave->eeprom_size < 16) {
+ EC_ERR("Failed to read EEPROM contents from slave %u.\n",
+ slave->ring_position);
+ return -EINVAL;
+ }
+
+ // copy first 7 words of recent EEPROM contents
+ memcpy(words, slave->eeprom_data, 14);
- // correct endianess
- EC_WRITE_U16(&word, alias);
+ // write new alias address
+ EC_WRITE_U16(words + 4, alias);
+
+ // calculate new checksum over words 0 to 6
+ crc = ec_slave_eeprom_crc((const uint8_t *) words, 14);
+ EC_WRITE_U16(words + 7, crc);
// init EEPROM write request
INIT_LIST_HEAD(&request.list);
request.slave = slave;
- request.words = &word;
- request.offset = 0x0004;
- request.size = 1;
+ request.words = words;
+ request.offset = 0x0000;
+ request.size = 8;
if ((ret = ec_slave_schedule_eeprom_writing(&request)))
return ret; // error code