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authorDavid Fries <david@fries.net>2008-10-15 22:04:42 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-16 11:21:49 -0700
commit6a158c0de791a81eb761ccf26ead1bd0834abac2 (patch)
treec4a35705bbeb2f90b81a5e5d44e9a7b45c2f666a /drivers/w1/w1.h
parent3c52e4e627896b42152cc6ff98216c302932227e (diff)
W1: feature, enable hardware strong pullup
Add a strong pullup option to the w1 system. This supplies extra power for parasite powered devices. There is a w1_master_pullup sysfs entry and enable_pullup module parameter to enable or disable the strong pullup. The one wire bus requires at a minimum one wire and ground. The common wire is used for sending and receiving data as well as supplying power to devices that are parasite powered of which temperature sensors can be one example. The bus must be idle and left high while a temperature conversion is in progress, in addition the normal pullup resister on larger networks or even higher temperatures might not supply enough power. The pullup resister can't provide too much pullup current, because devices need to pull the bus down to write a value. This enables the strong pullup for supported hardware, which can supply more current when requested. Unsupported hardware will just delay with the bus high. The hardware USB 2490 one wire bus master has a bit on some commands which will enable the strong pullup as soon as the command finishes executing. To use strong pullup, call the new w1_next_pullup function to register the duration. The next write command will call set_pullup before sending the data, and reset the duration to zero once it returns. Switched from simple_strtol to strict_strtol. Signed-off-by: David Fries <david@fries.net> Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/w1/w1.h')
-rw-r--r--drivers/w1/w1.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/w1/w1.h b/drivers/w1/w1.h
index 34ee01e008a..00b84ab2280 100644
--- a/drivers/w1/w1.h
+++ b/drivers/w1/w1.h
@@ -142,6 +142,12 @@ struct w1_bus_master
*/
u8 (*reset_bus)(void *);
+ /**
+ * Put out a strong pull-up pulse of the specified duration.
+ * @return -1=Error, 0=completed
+ */
+ u8 (*set_pullup)(void *, int);
+
/** Really nice hardware can handles the different types of ROM search
* w1_master* is passed to the slave found callback.
*/
@@ -167,6 +173,11 @@ struct w1_master
void *priv;
int priv_size;
+ /** 5V strong pullup enabled flag, 1 enabled, zero disabled. */
+ int enable_pullup;
+ /** 5V strong pullup duration in milliseconds, zero disabled. */
+ int pullup_duration;
+
struct task_struct *thread;
struct mutex mutex;
@@ -201,6 +212,7 @@ u8 w1_calc_crc8(u8 *, int);
void w1_write_block(struct w1_master *, const u8 *, int);
u8 w1_read_block(struct w1_master *, u8 *, int);
int w1_reset_select_slave(struct w1_slave *sl);
+void w1_next_pullup(struct w1_master *, int);
static inline struct w1_slave* dev_to_w1_slave(struct device *dev)
{