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 (file)
--- a/drivers/w1/slaves/Kconfig
+++ b/drivers/w1/slaves/Kconfig
@@ -22,6 +22,16 @@ config W1_SLAVE_DS2408
          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 (file)
--- a/drivers/w1/slaves/w1_ds2408.c
+++ b/drivers/w1/slaves/w1_ds2408.c
@@ -178,6 +178,15 @@ static ssize_t w1_f29_write_output(
                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 @@ static ssize_t w1_f29_write_output(
                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 @@ static ssize_t w1_f29_write_output(
                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,