w1: use family_data instead of rom in w1_slave

The first line printed from w1_slave gives the context of the w1
device.  So does the second line, but if the CRC check failed, the
second line contains the last successful result.  It is confusing when
it prints the temperature next to the line that might be a previous
conversion and has nothing to do with that printed temperature value.
Modify the code to store the last good conversion in family_data,
which is designed for custom data structures.
Signed-off-by: David Fries <David@Fries.net>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/w1/slaves/w1_therm.c

@@ -27,6 +27,7 @@
 #include <linux/sched.h>
 #include <linux/device.h>
 #include <linux/types.h>
+#include <linux/slab.h>
 #include <linux/delay.h>
 
 #include "../w1.h"
@@ -58,6 +59,19 @@ MODULE_ALIAS("w1-family-" __stringify(W1_THERM_DS28EA00));
 static int w1_strong_pullup = 1;
 module_param_named(strong_pullup, w1_strong_pullup, int, 0);
 
+static int w1_therm_add_slave(struct w1_slave *sl)
+{
+	sl->family_data = kzalloc(9, GFP_KERNEL);
+	if (!sl->family_data)
+		return -ENOMEM;
+	return 0;
+}
+
+static void w1_therm_remove_slave(struct w1_slave *sl)
+{
+	kfree(sl->family_data);
+	sl->family_data = NULL;
+}
 
 static ssize_t w1_slave_show(struct device *device,
 	struct device_attribute *attr, char *buf);
@@ -71,6 +85,8 @@ static struct attribute *w1_therm_attrs[] = {
 ATTRIBUTE_GROUPS(w1_therm);
 
 static struct w1_family_ops w1_therm_fops = {
+	.add_slave	= w1_therm_add_slave,
+	.remove_slave	= w1_therm_remove_slave,
 	.groups		= w1_therm_groups,
 };
 
@@ -253,12 +269,13 @@ static ssize_t w1_slave_show(struct device *device,
 	c -= snprintf(buf + PAGE_SIZE - c, c, ": crc=%02x %s\n",
 			   crc, (verdict) ? "YES" : "NO");
 	if (verdict)
-		memcpy(sl->rom, rom, sizeof(sl->rom));
+		memcpy(sl->family_data, rom, sizeof(rom));
 	else
 		dev_warn(device, "Read failed CRC check\n");
 
 	for (i = 0; i < 9; ++i)
-		c -= snprintf(buf + PAGE_SIZE - c, c, "%02x ", sl->rom[i]);
+		c -= snprintf(buf + PAGE_SIZE - c, c, "%02x ",
+			      ((u8 *)sl->family_data)[i]);
 
 	c -= snprintf(buf + PAGE_SIZE - c, c, "t=%d\n",
 		w1_convert_temp(rom, sl->family->fid));

drivers/w1/w1.h

@@ -67,7 +67,6 @@ struct w1_slave
 	struct list_head	w1_slave_entry;
 	struct w1_reg_num	reg_num;
 	atomic_t		refcnt;
-	u8			rom[9];
 	int			ttl;
 	unsigned long		flags;