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    Subject[PATCH 4.4 006/117] base/platform: Fix platform drivers with no probe callback
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Martin Wilck <Martin.Wilck@ts.fujitsu.com>

    commit 25cad69f21f5532d99e2ee73c8ab6512bcab614c upstream.

    Since b8b2c7d845d5, platform_drv_probe() is called for all platform
    devices. If drv->probe is NULL, and dev_pm_domain_attach() fails,
    platform_drv_probe() will return the error code from dev_pm_domain_attach().

    This causes real_probe() to enter the "probe_failed" path and set
    dev->driver to NULL. Before b8b2c7d845d5, real_probe() would assume
    success if both dev->bus->probe and drv->probe were missing. As a result,
    a device and driver could be "bound" together just by matching their names;
    this doesn't work any more after b8b2c7d845d5.

    This may cause problems later for certain usage of platform_driver_register()
    and platform_device_register_simple(). I observed a panic while loading
    the tpm_tis driver with parameter "force=1" (i.e. registering tpm_tis as
    a platform driver), because tpm_tis_init's assumption that the device
    returned by platform_device_register_simple() was bound didn't hold any more
    (tpmm_chip_alloc() dereferences chip->pdev->driver, causing panic).

    This patch restores the previous (4.3.0 and earlier) behavior of
    platform_drv_probe() in the case when the associated platform driver has
    no "probe" function.

    Fixes: b8b2c7d845d5 ("base/platform: assert that dev_pm_domain callbacks are called unconditionally")
    Signed-off-by: Martin Wilck <Martin.Wilck@ts.fujitsu.com>
    Cc: Martin Fuzzey <mfuzzey@parkeon.com>
    Acked-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/base/platform.c | 13 +++++++++----
    1 file changed, 9 insertions(+), 4 deletions(-)

    --- a/drivers/base/platform.c
    +++ b/drivers/base/platform.c
    @@ -513,10 +513,15 @@ static int platform_drv_probe(struct dev
    return ret;

    ret = dev_pm_domain_attach(_dev, true);
    - if (ret != -EPROBE_DEFER && drv->probe) {
    - ret = drv->probe(dev);
    - if (ret)
    - dev_pm_domain_detach(_dev, true);
    + if (ret != -EPROBE_DEFER) {
    + if (drv->probe) {
    + ret = drv->probe(dev);
    + if (ret)
    + dev_pm_domain_detach(_dev, true);
    + } else {
    + /* don't fail if just dev_pm_domain_attach failed */
    + ret = 0;
    + }
    }

    if (drv->prevent_deferred_probe && ret == -EPROBE_DEFER) {

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