[PATCH] w1: Add 1-wire reset and resume API (0xA5)

[Jean-François Dagenais]

from: Jean-François Dagenais <jeff.dagenais@xxxxxxxxx>

add generic functionnality to w1_io for Resume Command [A5h]
lots of slaves support. It is useful for multi-commands/reset workflows
with the same slave on a multi-slave bus where reset-skip-ROM is
inappropriate.

Signed-off-by: Jean-François Dagenais <jeff.dagenais@xxxxxxxxx>
---
:100644 100644 d8a9709... f804eba... M	drivers/w1/w1.h
:100644 100644 3ebe972... 8e8b64c... M	drivers/w1/w1_io.c
drivers/w1/w1.h    |    2 ++
drivers/w1/w1_io.c |   26 ++++++++++++++++++++++++++
2 files changed, 28 insertions(+), 0 deletions(-)

diff --git a/drivers/w1/w1.h b/drivers/w1/w1.h
index d8a9709..f804eba 100644
--- a/drivers/w1/w1.h
+++ b/drivers/w1/w1.h
@@ -55,6 +55,7 @@ struct w1_reg_num
#define W1_READ_ROM		0x33
#define W1_READ_PSUPPLY		0xB4
#define W1_MATCH_ROM		0x55
+#define W1_RESUME_CMD		0xA5

#define W1_SLAVE_ACTIVE		0

@@ -213,6 +214,7 @@ void w1_write_block(struct w1_master *, const u8 *, int);
void w1_touch_block(struct w1_master *, u8 *, int);
u8 w1_read_block(struct w1_master *, u8 *, int);
int w1_reset_select_slave(struct w1_slave *sl);
+int w1_reset_resume_command(struct w1_master *);
void w1_next_pullup(struct w1_master *, int);

static inline struct w1_slave* dev_to_w1_slave(struct device *dev)
diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c
index 3ebe972..8e8b64c 100644
--- a/drivers/w1/w1_io.c
+++ b/drivers/w1/w1_io.c
@@ -390,6 +390,32 @@ 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
 * doesn't support strong pullups will sleep for the given time after the
-- 
1.7.4.1

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