w1: ds2408: make value read-back check a Kconfig option
De-activating this reading back will effectively half the time required
for a write to the output register.
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Jean-Francois Dagenais <jeff.dagenais@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/w1/slaves/Kconfig b/drivers/w1/slaves/Kconfig
index 762561f..5e6a3c9 100644
--- a/drivers/w1/slaves/Kconfig
+++ b/drivers/w1/slaves/Kconfig
@@ -22,6 +22,16 @@
Say Y here if you want to use a 1-wire
DS2408 8-Channel Addressable Switch device support
+config W1_SLAVE_DS2408_READBACK
+ bool "Read-back values written to DS2408's output register"
+ depends on W1_SLAVE_DS2408
+ default y
+ help
+ Enabling this will cause the driver to read back the values written
+ to the chip's output register in order to detect errors.
+
+ This is slower but useful when debugging chips and/or busses.
+
config W1_SLAVE_DS2413
tristate "Dual Channel Addressable Switch 0x3a family support (DS2413)"
help
diff --git a/drivers/w1/slaves/w1_ds2408.c b/drivers/w1/slaves/w1_ds2408.c
index 441ad3a..25a5168 100644
--- a/drivers/w1/slaves/w1_ds2408.c
+++ b/drivers/w1/slaves/w1_ds2408.c
@@ -178,6 +178,15 @@
w1_write_block(sl->master, w1_buf, 3);
readBack = w1_read_8(sl->master);
+
+ if (readBack != W1_F29_SUCCESS_CONFIRM_BYTE) {
+ if (w1_reset_resume_command(sl->master))
+ goto error;
+ /* try again, the slave is ready for a command */
+ continue;
+ }
+
+#ifdef CONFIG_W1_SLAVE_DS2408_READBACK
/* here the master could read another byte which
would be the PIO reg (the actual pin logic state)
since in this driver we don't know which pins are
@@ -186,11 +195,6 @@
if (w1_reset_resume_command(sl->master))
goto error;
- if (readBack != 0xAA) {
- /* try again, the slave is ready for a command */
- continue;
- }
-
/* go read back the output latches */
/* (the direct effect of the write above) */
w1_buf[0] = W1_F29_FUNC_READ_PIO_REGS;
@@ -198,7 +202,9 @@
w1_buf[2] = 0;
w1_write_block(sl->master, w1_buf, 3);
/* read the result of the READ_PIO_REGS command */
- if (w1_read_8(sl->master) == *buf) {
+ if (w1_read_8(sl->master) == *buf)
+#endif
+ {
/* success! */
mutex_unlock(&sl->master->bus_mutex);
dev_dbg(&sl->dev,