Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid

[cascardo/linux.git] / drivers / w1 / w1_io.c

diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c
index 3ebe972..8e8b64c 100644 (file)
--- a/drivers/w1/w1_io.c
+++ b/drivers/w1/w1_io.c
@@ -389,6 +389,32 @@ int w1_reset_select_slave(struct w1_slave *sl)
 }
 EXPORT_SYMBOL_GPL(w1_reset_select_slave);
 
+/**
+ * When the workflow with a slave amongst many requires several
+ * successive commands a reset between each, this function is similar
+ * to doing a reset then a match ROM for the last matched ROM. The
+ * advantage being that the matched ROM step is skipped in favor of the
+ * resume command. The slave must support the command of course.
+ *
+ * If the bus has only one slave, traditionnaly the match ROM is skipped
+ * and a "SKIP ROM" is done for efficiency. On multi-slave busses, this
+ * doesn't work of course, but the resume command is the next best thing.
+ *
+ * The w1 master lock must be held.
+ *
+ * @param dev     the master device
+ */
+int w1_reset_resume_command(struct w1_master *dev)
+{
+       if (w1_reset_bus(dev))
+               return -1;
+
+       /* This will make only the last matched slave perform a skip ROM. */
+       w1_write_8(dev, W1_RESUME_CMD);
+       return 0;
+}
+EXPORT_SYMBOL_GPL(w1_reset_resume_command);
+
 /**
  * Put out a strong pull-up of the specified duration after the next write
  * operation.  Not all hardware supports strong pullups.  Hardware that