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    Subject[PATCH] pinctrl: implement pinctrl deferred probing
    Date
    From: Linus Walleij <linus.walleij@linaro.org>

    If drivers try to obtain pinctrl handles for a pin controller that
    has not yet registered to the subsystem, we need to be able to
    back out and retry with deferred probing. So let's return
    -EPROBE_DEFER whenever this location fails.

    Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
    Cc: Arnd Bergmann <arnd@arndb.de>
    Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
    ---
    Documentation/pinctrl.txt | 5 +++++
    drivers/pinctrl/core.c | 7 +++++--
    drivers/pinctrl/devicetree.c | 4 ++--
    3 files changed, 12 insertions(+), 4 deletions(-)

    diff --git a/Documentation/pinctrl.txt b/Documentation/pinctrl.txt
    index eb46b1c..4431c3e7 100644
    --- a/Documentation/pinctrl.txt
    +++ b/Documentation/pinctrl.txt
    @@ -1043,6 +1043,11 @@ quickly poking some registers.
    The pins are allocated for your device when you issue the pinctrl_get() call,
    after this you should be able to see this in the debugfs listing of all pins.

    +NOTE: the pinctrl system will return -EPROBE_DEFER if it cannot find the
    +requested pinctrl handles, for example if the pinctrl driver has not yet
    +registered. Thus make sure that the error path in your driver gracefully
    +cleans up and is ready to retry the probing later in the startup process.
    +

    System pin control hogging
    ==========================
    diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
    index 7ff8690..3ae00ab 100644
    --- a/drivers/pinctrl/core.c
    +++ b/drivers/pinctrl/core.c
    @@ -521,8 +521,11 @@ static int add_setting(struct pinctrl *p, struct pinctrl_map const *map)
    dev_err(p->dev, "unknown pinctrl device %s in map entry",
    map->ctrl_dev_name);
    kfree(setting);
    - /* Eventually, this should trigger deferred probe */
    - return -ENODEV;
    + /*
    + * OK let us guess that the driver is not there yet, and
    + * let's defer obtaining this pinctrl handle to later...
    + */
    + return -EPROBE_DEFER;
    }

    switch (map->type) {
    diff --git a/drivers/pinctrl/devicetree.c b/drivers/pinctrl/devicetree.c
    index 5ef2feb..8833538 100644
    --- a/drivers/pinctrl/devicetree.c
    +++ b/drivers/pinctrl/devicetree.c
    @@ -124,8 +124,8 @@ static int dt_to_map_one_config(struct pinctrl *p, const char *statename,
    dev_err(p->dev, "could not find pctldev for node %s\n",
    np_config->full_name);
    of_node_put(np_pctldev);
    - /* FIXME: This should trigger deferrered probe */
    - return -ENODEV;
    + /* OK let's just assume this will appear later then */
    + return -EPROBE_DEFER;
    }
    pctldev = find_pinctrl_by_of_node(np_pctldev);
    if (pctldev)
    --
    1.7.9.2


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