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    Subject[PATCH 1/3] spi: Revert "spi: Remove unused function spi_busnum_to_master()"
    Date
    From: Lucas Tanure <tanureal@opensource.cirrus.com>

    Revert commit bdc7ca008e1f ("spi: Remove unused function
    spi_busnum_to_master()")
    This function is needed for the spi version of i2c multi
    instantiate driver.

    Signed-off-by: Lucas Tanure <tanureal@opensource.cirrus.com>
    Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
    ---
    Documentation/spi/spi-summary.rst | 8 +++++++
    drivers/spi/spi.c | 35 +++++++++++++++++++++++++++++++
    include/linux/spi/spi.h | 2 ++
    3 files changed, 45 insertions(+)

    diff --git a/Documentation/spi/spi-summary.rst b/Documentation/spi/spi-summary.rst
    index aab5d07cb3d7..d4239025461d 100644
    --- a/Documentation/spi/spi-summary.rst
    +++ b/Documentation/spi/spi-summary.rst
    @@ -336,6 +336,14 @@ certainly includes SPI devices hooked up through the card connectors!
    Non-static Configurations
    ^^^^^^^^^^^^^^^^^^^^^^^^^

    +Developer boards often play by different rules than product boards, and one
    +example is the potential need to hotplug SPI devices and/or controllers.
    +
    +For those cases you might need to use spi_busnum_to_master() to look
    +up the spi bus master, and will likely need spi_new_device() to provide the
    +board info based on the board that was hotplugged. Of course, you'd later
    +call at least spi_unregister_device() when that board is removed.
    +
    When Linux includes support for MMC/SD/SDIO/DataFlash cards through SPI, those
    configurations will also be dynamic. Fortunately, such devices all support
    basic device identification probes, so they should hotplug normally.
    diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
    index 8726309b3eaf..7c81173edb0c 100644
    --- a/drivers/spi/spi.c
    +++ b/drivers/spi/spi.c
    @@ -3145,6 +3145,41 @@ int spi_controller_resume(struct spi_controller *ctlr)
    }
    EXPORT_SYMBOL_GPL(spi_controller_resume);

    +static int __spi_controller_match(struct device *dev, const void *data)
    +{
    + struct spi_controller *ctlr;
    + const u16 *bus_num = data;
    +
    + ctlr = container_of(dev, struct spi_controller, dev);
    + return ctlr->bus_num == *bus_num;
    +}
    +
    +/**
    + * spi_busnum_to_master - look up master associated with bus_num
    + * @bus_num: the master's bus number
    + * Context: can sleep
    + *
    + * This call may be used with devices that are registered after
    + * arch init time. It returns a refcounted pointer to the relevant
    + * spi_controller (which the caller must release), or NULL if there is
    + * no such master registered.
    + *
    + * Return: the SPI master structure on success, else NULL.
    + */
    +struct spi_controller *spi_busnum_to_master(u16 bus_num)
    +{
    + struct device *dev;
    + struct spi_controller *ctlr = NULL;
    +
    + dev = class_find_device(&spi_master_class, NULL, &bus_num,
    + __spi_controller_match);
    + if (dev)
    + ctlr = container_of(dev, struct spi_controller, dev);
    + /* reference got in class_find_device */
    + return ctlr;
    +}
    +EXPORT_SYMBOL_GPL(spi_busnum_to_master);
    +
    /*-------------------------------------------------------------------------*/

    /* Core methods for spi_message alterations */
    diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
    index eb7ac8a1e03c..5f2781cb750f 100644
    --- a/include/linux/spi/spi.h
    +++ b/include/linux/spi/spi.h
    @@ -759,6 +759,8 @@ extern int devm_spi_register_controller(struct device *dev,
    struct spi_controller *ctlr);
    extern void spi_unregister_controller(struct spi_controller *ctlr);

    +extern struct spi_controller *spi_busnum_to_master(u16 busnum);
    +
    /*
    * SPI resource management while processing a SPI message
    */
    --
    2.25.1
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