1 files changed, 16 insertions, 20 deletions

diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index 92d08e7fcba2..c1a702f8c803 100644
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -41,14 +41,18 @@ MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol, temperature famil
  * If it was disabled a parasite powered device might not get the require
  * current to do a temperature conversion.  If it is enabled parasite powered
  * devices have a better chance of getting the current required.
+ * In case the parasite power-detection is not working (seems to be the case
+ * for some DS18S20) the strong pullup can also be forced, regardless of the
+ * power state of the devices.
+ *
+ * Summary of options:
+ * - strong_pullup = 0  Disable strong pullup completely
+ * - strong_pullup = 1  Enable automatic strong pullup detection
+ * - strong_pullup = 2  Force strong pullup
  */
 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 +172,6 @@ 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 +188,11 @@ 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;
@@ -210,7 +205,8 @@ static ssize_t w1_therm_read(struct device *device,
                                 continue;
 
                         /* 750ms strong pullup (or delay) after the convert */
-                        if (!external_power && w1_strong_pullup)
+                        if (w1_strong_pullup == 2 ||
+                                        (!external_power && w1_strong_pullup))
                                 w1_next_pullup(dev, tm);
 
                         w1_write_8(dev, W1_CONVERT_TEMP);
@@ -249,7 +245,7 @@ static ssize_t w1_therm_read(struct device *device,
                         }
                 }
 
-                if (!w1_therm_check_rom(rom))
+                if (verdict)
                         break;
         }
 
@@ -260,7 +256,7 @@ 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]);