Re: device model documentation 2/3

Pavel Machek
2002-06-05T20:17:21Z

Hi!

> int (*remove) (struct device * dev);
>
> remove is called to dissociate a driver with a device. This may be
> called if a device is physically removed from the system, if the
> driver module is being unloaded, or during a reboot sequence.
>
> It is up to the driver to determine if the device is present or
> not. It should free any resources allocated specifically for the
> device; i.e. anything in the device's driver_data field.
>
> If the device is still present, it should quiesce the device and place
> it into a supported low-power state.

"returns 0 == success or error code, and may block."

> int (*suspend) (struct device * dev, u32 state, u32 level);
>
> suspend is called to put the device in a low power state. There are
> several stages to sucessfully suspending a device, which is denoted in
> the @level parameter. Breaking the suspend transition into several
> stages affords the platform flexibility in performing device power
> management based on the requirements of the system and the
> user-defined policy.

"returns 0 == success or error code"

> SUSPEND_NOTIFY notifies the device that a suspend transition is about
> to happen. This happens on system power state transition to verify
> that all devices can sucessfully suspend.
>
> A driver may choose to fail on this call, which should cause the
> entire suspend transition to fail. A driver should fail only if it
> knows that the device will not be able to be resumed properly when the
> system wakes up again. It could also fail if it somehow determines it
> is in the middle of an operation too important to stop.

??? If it is in the middle of important operation, it should just yield()
waiting for operation to finish.

> SUSPEND_DISABLE tells the device to stop I/O transactions. When it
> stops transactions, or what it should do with unfinished transactions
> is a policy of the driver. After this call, the driver should not
> accept any other I/O requests.

I believe higher levels should make it so that no new requests are submitted.
We do not want each and every driver to implement its own (buggy!) method for
this.

Pavel
--
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