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    Subject[PATCH] w1: Add 1-wire reset and resume API (0xA5)
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    from: Jean-François Dagenais <jeff.dagenais@gmail.com>

    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@gmail.com>
    ---
    :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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