w1_therm: Retries: remove old code add CRC

w1_therm includes some obsolete code to detect bad_roms, this is no
longer relevant.
The retry code is only used for this bad_rom test, however there is a
CRC check that detects a bad read, but does not trigger a retry. This
patch removes all the bad_rom code and uses the CRC check to trigger
retries.

Signed-off-by: David Stevenson <david@avoncliff.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/w1/slaves/w1_therm.c

@@ -45,10 +45,6 @@ MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol, temperature famil
 static int w1_strong_pullup = 1;
 module_param_named(strong_pullup, w1_strong_pullup, int, 0);
 
-static u8 bad_roms[][9] = {
-				{0xaa, 0x00, 0x4b, 0x46, 0xff, 0xff, 0x0c, 0x10, 0x87},
-				{}
-			};
 
 static ssize_t w1_therm_read(struct device *device,
 	struct device_attribute *attr, char *buf);
@@ -168,16 +164,6 @@ static inline int w1_convert_temp(u8 rom[9], u8 fid)
 	return 0;
 }
 
-static int w1_therm_check_rom(u8 rom[9])
-{
-	int i;
-
-	for (i=0; i<sizeof(bad_roms)/9; ++i)
-		if (!memcmp(bad_roms[i], rom, 9))
-			return 1;
-
-	return 0;
-}
 
 static ssize_t w1_therm_read(struct device *device,
 	struct device_attribute *attr, char *buf)
@@ -194,10 +180,11 @@ static ssize_t w1_therm_read(struct device *device,
 
 	memset(rom, 0, sizeof(rom));
 
-	verdict = 0;
-	crc = 0;
-
 	while (max_trying--) {
+
+		verdict = 0;
+		crc = 0;
+
 		if (!w1_reset_select_slave(sl)) {
 			int count = 0;
 			unsigned int tm = 750;
@@ -249,7 +236,7 @@ static ssize_t w1_therm_read(struct device *device,
 			}
 		}
 
-		if (!w1_therm_check_rom(rom))
+		if (verdict)
 			break;
 	}
 
@@ -260,7 +247,7 @@ static ssize_t w1_therm_read(struct device *device,
 	if (verdict)
 		memcpy(sl->rom, rom, sizeof(sl->rom));
 	else
-		dev_warn(device, "18S20 doesn't respond to CONVERT_TEMP.\n");
+		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]);