+ /*
+ * Hosts that support power saving can use the 'enable' and 'disable'
+ * methods to exit and enter power saving states. 'enable' is called
+ * when the host is claimed and 'disable' is called (or scheduled with
+ * a delay) when the host is released. The 'disable' is scheduled if
+ * the disable delay set by 'mmc_set_disable_delay()' is non-zero,
+ * otherwise 'disable' is called immediately. 'disable' may be
+ * scheduled repeatedly, to permit ever greater power saving at the
+ * expense of ever greater latency to re-enable. Rescheduling is
+ * determined by the return value of the 'disable' method. A positive
+ * value gives the delay in milliseconds.
+ *
+ * In the case where a host function (like set_ios) may be called
+ * with or without the host claimed, enabling and disabling can be
+ * done directly and will nest correctly. Call 'mmc_host_enable()' and
+ * 'mmc_host_lazy_disable()' for this purpose, but note that these
+ * functions must be paired.
+ *
+ * Alternatively, 'mmc_host_enable()' may be paired with
+ * 'mmc_host_disable()' which calls 'disable' immediately. In this
+ * case the 'disable' method will be called with 'lazy' set to 0.
+ * This is mainly useful for error paths.
+ *
+ * Because lazy disable may be called from a work queue, the 'disable'
+ * method must claim the host when 'lazy' != 0, which will work
+ * correctly because recursion is detected and handled.
+ */
+ int (*enable)(struct mmc_host *host);
+ int (*disable)(struct mmc_host *host, int lazy);