w1: add ability to set (SRAM) and store (EEPROM) configuration for temp sensors like DS18B20
Since many temperature sensors come "preconfigured" with a lower
precision, people are stuck at that precision when running on a kernel
based device (unlike the Dallas 1Wire library for e.g. Arduino, which
supports writing the configuration/scratchpad). This patch adds write
support for the scratchpad/precision registers via w1_slave sysfs.
Signed-off-by: Ben Sen <0.x29a.0@gmail.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index 2f029e8..581a300 100644
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -92,10 +92,13 @@
static ssize_t w1_slave_show(struct device *device,
struct device_attribute *attr, char *buf);
+static ssize_t w1_slave_store(struct device *device,
+ struct device_attribute *attr, const char *buf, size_t size);
+
static ssize_t w1_seq_show(struct device *device,
struct device_attribute *attr, char *buf);
-static DEVICE_ATTR_RO(w1_slave);
+static DEVICE_ATTR_RW(w1_slave);
static DEVICE_ATTR_RO(w1_seq);
static struct attribute *w1_therm_attrs[] = {
@@ -154,8 +157,17 @@
u16 reserved;
struct w1_family *f;
int (*convert)(u8 rom[9]);
+ int (*precision)(struct device *device, int val);
+ int (*eeprom)(struct device *device);
};
+/* write configuration to eeprom */
+static inline int w1_therm_eeprom(struct device *device);
+
+/* Set precision for conversion */
+static inline int w1_DS18B20_precision(struct device *device, int val);
+static inline int w1_DS18S20_precision(struct device *device, int val);
+
/* The return value is millidegrees Centigrade. */
static inline int w1_DS18B20_convert_temp(u8 rom[9]);
static inline int w1_DS18S20_convert_temp(u8 rom[9]);
@@ -163,26 +175,194 @@
static struct w1_therm_family_converter w1_therm_families[] = {
{
.f = &w1_therm_family_DS18S20,
- .convert = w1_DS18S20_convert_temp
+ .convert = w1_DS18S20_convert_temp,
+ .precision = w1_DS18S20_precision,
+ .eeprom = w1_therm_eeprom
},
{
.f = &w1_therm_family_DS1822,
- .convert = w1_DS18B20_convert_temp
+ .convert = w1_DS18B20_convert_temp,
+ .precision = w1_DS18S20_precision,
+ .eeprom = w1_therm_eeprom
},
{
.f = &w1_therm_family_DS18B20,
- .convert = w1_DS18B20_convert_temp
+ .convert = w1_DS18B20_convert_temp,
+ .precision = w1_DS18B20_precision,
+ .eeprom = w1_therm_eeprom
},
{
.f = &w1_therm_family_DS28EA00,
- .convert = w1_DS18B20_convert_temp
+ .convert = w1_DS18B20_convert_temp,
+ .precision = w1_DS18S20_precision,
+ .eeprom = w1_therm_eeprom
},
{
.f = &w1_therm_family_DS1825,
- .convert = w1_DS18B20_convert_temp
+ .convert = w1_DS18B20_convert_temp,
+ .precision = w1_DS18S20_precision,
+ .eeprom = w1_therm_eeprom
}
};
+static inline int w1_therm_eeprom(struct device *device)
+{
+ struct w1_slave *sl = dev_to_w1_slave(device);
+ struct w1_master *dev = sl->master;
+ u8 rom[9], external_power;
+ int ret, max_trying = 10;
+ u8 *family_data = sl->family_data;
+
+ ret = mutex_lock_interruptible(&dev->bus_mutex);
+ if (ret != 0)
+ goto post_unlock;
+
+ if (!sl->family_data) {
+ ret = -ENODEV;
+ goto pre_unlock;
+ }
+
+ /* prevent the slave from going away in sleep */
+ atomic_inc(THERM_REFCNT(family_data));
+ memset(rom, 0, sizeof(rom));
+
+ while (max_trying--) {
+ if (!w1_reset_select_slave(sl)) {
+ unsigned int tm = 10;
+ unsigned long sleep_rem;
+
+ /* check if in parasite mode */
+ w1_write_8(dev, W1_READ_PSUPPLY);
+ external_power = w1_read_8(dev);
+
+ if (w1_reset_select_slave(sl))
+ continue;
+
+ /* 10ms strong pullup/delay after the copy command */
+ if (w1_strong_pullup == 2 ||
+ (!external_power && w1_strong_pullup))
+ w1_next_pullup(dev, tm);
+
+ w1_write_8(dev, W1_COPY_SCRATCHPAD);
+
+ if (external_power) {
+ mutex_unlock(&dev->bus_mutex);
+
+ sleep_rem = msleep_interruptible(tm);
+ if (sleep_rem != 0) {
+ ret = -EINTR;
+ goto post_unlock;
+ }
+
+ ret = mutex_lock_interruptible(&dev->bus_mutex);
+ if (ret != 0)
+ goto post_unlock;
+ } else if (!w1_strong_pullup) {
+ sleep_rem = msleep_interruptible(tm);
+ if (sleep_rem != 0) {
+ ret = -EINTR;
+ goto pre_unlock;
+ }
+ }
+
+ break;
+ }
+ }
+
+pre_unlock:
+ mutex_unlock(&dev->bus_mutex);
+
+post_unlock:
+ atomic_dec(THERM_REFCNT(family_data));
+ return ret;
+}
+
+/* DS18S20 does not feature configuration register */
+static inline int w1_DS18S20_precision(struct device *device, int val)
+{
+ return 0;
+}
+
+static inline int w1_DS18B20_precision(struct device *device, int val)
+{
+ struct w1_slave *sl = dev_to_w1_slave(device);
+ struct w1_master *dev = sl->master;
+ u8 rom[9], crc;
+ int ret, max_trying = 10;
+ u8 *family_data = sl->family_data;
+ uint8_t precision_bits;
+ uint8_t mask = 0x60;
+
+ if(val > 12 || val < 9) {
+ pr_warn("Unsupported precision\n");
+ return -1;
+ }
+
+ ret = mutex_lock_interruptible(&dev->bus_mutex);
+ if (ret != 0)
+ goto post_unlock;
+
+ if (!sl->family_data) {
+ ret = -ENODEV;
+ goto pre_unlock;
+ }
+
+ /* prevent the slave from going away in sleep */
+ atomic_inc(THERM_REFCNT(family_data));
+ memset(rom, 0, sizeof(rom));
+
+ /* translate precision to bitmask (see datasheet page 9) */
+ switch (val) {
+ case 9:
+ precision_bits = 0x00;
+ break;
+ case 10:
+ precision_bits = 0x20;
+ break;
+ case 11:
+ precision_bits = 0x40;
+ break;
+ case 12:
+ default:
+ precision_bits = 0x60;
+ break;
+ }
+
+ while (max_trying--) {
+ crc = 0;
+
+ if (!w1_reset_select_slave(sl)) {
+ int count = 0;
+
+ /* read values to only alter precision bits */
+ w1_write_8(dev, W1_READ_SCRATCHPAD);
+ if ((count = w1_read_block(dev, rom, 9)) != 9)
+ dev_warn(device, "w1_read_block() returned %u instead of 9.\n", count);
+
+ crc = w1_calc_crc8(rom, 8);
+ if (rom[8] == crc) {
+ rom[4] = (rom[4] & ~mask) | (precision_bits & mask);
+
+ if (!w1_reset_select_slave(sl)) {
+ w1_write_8(dev, W1_WRITE_SCRATCHPAD);
+ w1_write_8(dev, rom[2]);
+ w1_write_8(dev, rom[3]);
+ w1_write_8(dev, rom[4]);
+
+ break;
+ }
+ }
+ }
+ }
+
+pre_unlock:
+ mutex_unlock(&dev->bus_mutex);
+
+post_unlock:
+ atomic_dec(THERM_REFCNT(family_data));
+ return ret;
+}
+
static inline int w1_DS18B20_convert_temp(u8 rom[9])
{
s16 t = le16_to_cpup((__le16 *)rom);
@@ -220,6 +400,30 @@
return 0;
}
+static ssize_t w1_slave_store(struct device *device,
+ struct device_attribute *attr, const char *buf,
+ size_t size)
+{
+ int val, ret;
+ struct w1_slave *sl = dev_to_w1_slave(device);
+ int i;
+
+ ret = kstrtoint(buf, 0, &val);
+ if (ret)
+ return ret;
+
+ for (i = 0; i < ARRAY_SIZE(w1_therm_families); ++i) {
+ if (w1_therm_families[i].f->fid == sl->family->fid) {
+ /* zero value indicates to write current configuration to eeprom */
+ if (0 == val)
+ ret = w1_therm_families[i].eeprom(device);
+ else
+ ret = w1_therm_families[i].precision(device, val);
+ break;
+ }
+ }
+ return ret ? : size;
+}
static ssize_t w1_slave_show(struct device *device,
struct device_attribute *attr, char *buf)
@@ -311,7 +515,7 @@
for (i = 0; i < 9; ++i)
c -= snprintf(buf + PAGE_SIZE - c, c, "%02x ", rom[i]);
c -= snprintf(buf + PAGE_SIZE - c, c, ": crc=%02x %s\n",
- crc, (verdict) ? "YES" : "NO");
+ crc, (verdict) ? "YES" : "NO");
if (verdict)
memcpy(family_data, rom, sizeof(rom));
else
diff --git a/drivers/w1/w1.h b/drivers/w1/w1.h
index 56a49ba..129895f 100644
--- a/drivers/w1/w1.h
+++ b/drivers/w1/w1.h
@@ -58,6 +58,8 @@
#define W1_ALARM_SEARCH 0xEC
#define W1_CONVERT_TEMP 0x44
#define W1_SKIP_ROM 0xCC
+#define W1_COPY_SCRATCHPAD 0x48
+#define W1_WRITE_SCRATCHPAD 0x4E
#define W1_READ_SCRATCHPAD 0xBE
#define W1_READ_ROM 0x33
#define W1_READ_PSUPPLY 0xB4