+#define W1_42_CHAIN 0x99
+#define W1_42_CHAIN_OFF 0x3C
+#define W1_42_CHAIN_OFF_INV 0xC3
+#define W1_42_CHAIN_ON 0x5A
+#define W1_42_CHAIN_ON_INV 0xA5
+#define W1_42_CHAIN_DONE 0x96
+#define W1_42_CHAIN_DONE_INV 0x69
+#define W1_42_COND_READ 0x0F
+#define W1_42_SUCCESS_CONFIRM_BYTE 0xAA
+#define W1_42_FINISHED_BYTE 0xFF
+static ssize_t w1_seq_show(struct device *device,
+ struct device_attribute *attr, char *buf)
+{
+ struct w1_slave *sl = dev_to_w1_slave(device);
+ ssize_t c = PAGE_SIZE;
+ int rv;
+ int i;
+ u8 ack;
+ u64 rn;
+ struct w1_reg_num *reg_num;
+ int seq = 0;
+
+ mutex_lock(&sl->master->bus_mutex);
+ /* Place all devices in CHAIN state */
+ if (w1_reset_bus(sl->master))
+ goto error;
+ w1_write_8(sl->master, W1_SKIP_ROM);
+ w1_write_8(sl->master, W1_42_CHAIN);
+ w1_write_8(sl->master, W1_42_CHAIN_ON);
+ w1_write_8(sl->master, W1_42_CHAIN_ON_INV);
+ msleep(sl->master->pullup_duration);
+
+ /* check for acknowledgment */
+ ack = w1_read_8(sl->master);
+ if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
+ goto error;
+
+ /* In case the bus fails to send 0xFF, limit*/
+ for (i = 0; i <= 64; i++) {
+ if (w1_reset_bus(sl->master))
+ goto error;
+
+ w1_write_8(sl->master, W1_42_COND_READ);
+ rv = w1_read_block(sl->master, (u8 *)&rn, 8);
+ reg_num = (struct w1_reg_num *) &rn;
+ if (reg_num->family == W1_42_FINISHED_BYTE)
+ break;
+ if (sl->reg_num.id == reg_num->id)
+ seq = i;
+
+ w1_write_8(sl->master, W1_42_CHAIN);
+ w1_write_8(sl->master, W1_42_CHAIN_DONE);
+ w1_write_8(sl->master, W1_42_CHAIN_DONE_INV);
+ w1_read_block(sl->master, &ack, sizeof(ack));
+
+ /* check for acknowledgment */
+ ack = w1_read_8(sl->master);
+ if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
+ goto error;
+
+ }
+
+ /* Exit from CHAIN state */
+ if (w1_reset_bus(sl->master))
+ goto error;
+ w1_write_8(sl->master, W1_SKIP_ROM);
+ w1_write_8(sl->master, W1_42_CHAIN);
+ w1_write_8(sl->master, W1_42_CHAIN_OFF);
+ w1_write_8(sl->master, W1_42_CHAIN_OFF_INV);
+
+ /* check for acknowledgment */
+ ack = w1_read_8(sl->master);
+ if (ack != W1_42_SUCCESS_CONFIRM_BYTE)
+ goto error;
+ mutex_unlock(&sl->master->bus_mutex);
+
+ c -= snprintf(buf + PAGE_SIZE - c, c, "%d\n", seq);
+ return PAGE_SIZE - c;
+error:
+ mutex_unlock(&sl->master->bus_mutex);
+ return -EIO;
+}
+