Block Driver Power Cycle

Article
06/30/2006

The power management protocol supports power cycles that are transparent to applications. Therefore, it is important that block device drivers handle the POWER_DOWN and POWER_UP system messages efficiently.

Like all device drivers, block device drivers must limit themselves to minimal, very fast processing of the POWER_DOWN message. To accomplish this, they should save any volatile state information in RAM, set a flag to indicate that power is about to turn off, and then exit.

POWER_ON processing is exactly like the processing for a regular card removal that follows an insertion. When power resumes, the PC Card Socket driver issues a card-removal notification for all sockets with inserted cards. For more information about PC Card Socket drivers, see PC Card Drivers. Next, it checks the socket status and issues card-insertion notices for each socket with a card. Then, the Device Manager launches its detection sequence and loads the appropriate driver for each card. For more information about the Device Manager, see Device Manager.

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Block Driver Power Cycle

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