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    SubjectRe: [RFC PATCH v4 7/8] pwm: Add dummy pwmchip for orphan pwms
    On Tue, Oct 17, 2017 at 06:16:23PM +0800, Jeffy Chen wrote:
    > When the pwm driver is unbound while the pwm is still requested, the
    > pwm core would not actually remove the pwmchip(return -EBUSY instead).
    >
    > So it would hold some references to the invalid resources(e.g. pwmchip).
    >
    > And the customer who requested the pwm would have those references too,
    > and may crash the kernel when trying to access them later.
    >
    > Add a dummy pwmchip, and assign orphan pwms to it to avoid that.
    >
    > Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
    > ---
    >
    > Changes in v4:
    > Fix compile warning.
    >
    > Changes in v3:
    > Assign orphan pwms to dummy pwmchip instead of adding device link in the
    > customer driver.

    What happened to this? Device links were specifically designed to avoid
    situations like these.

    A dummy PWM chip doesn't seem like the right solution to this.

    Thierry
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