include/hw/ptimer.h: Add documentation comments (a7a305ae) · Commits · SUMMER2020 / students / proj-2021291

include/hw/ptimer.h

+120 −0

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		@@ -12,6 +12,20 @@
		#include "qemu/timer.h"
		#include "migration/vmstate.h"

		/* The ptimer API implements a simple periodic countdown timer.
		* The countdown timer has a value (which can be read and written via
		* ptimer_get_count() and ptimer_set_count()). When it is enabled
		* using ptimer_run(), the value will count downwards at the frequency
		* which has been configured using ptimer_set_period() or ptimer_set_freq().
		* When it reaches zero it will trigger a QEMU bottom half handler, and
		* can be set to either reload itself from a specified limit value
		* and keep counting down, or to stop (as a one-shot timer).
		*
		* Forgetting to set the period/frequency (or setting it to zero) is a
		* bug in the QEMU device and will cause warning messages to be printed
		* to stderr when the guest attempts to enable the timer.
		*/

		/* The default ptimer policy retains backward compatibility with the legacy
		* timers. Custom policies are adjusting the default one. Consider providing
		* a correct policy for your timer.
		@@ -59,15 +73,121 @@
		typedef struct ptimer_state ptimer_state;
		typedef void (ptimer_cb)(void opaque);

		/**
		* ptimer_init - Allocate and return a new ptimer
		* @bh: QEMU bottom half which is run on timer expiry
		* @policy: PTIMER_POLICY_* bits specifying behaviour
		*
		* The ptimer returned must be freed using ptimer_free().
		* The ptimer takes ownership of @bh and will delete it
		* when the ptimer is eventually freed.
		*/
		ptimer_state ptimer_init(QEMUBH bh, uint8_t policy_mask);

		/**
		* ptimer_free - Free a ptimer
		* @s: timer to free
		*
		* Free a ptimer created using ptimer_init() (including
		* deleting the bottom half which it is using).
		*/
		void ptimer_free(ptimer_state *s);

		/**
		* ptimer_set_period - Set counter increment interval in nanoseconds
		* @s: ptimer to configure
		* @period: period of the counter in nanoseconds
		*
		* Note that if your counter behaviour is specified as having a
		* particular frequency rather than a period then ptimer_set_freq()
		* may be more appropriate.
		*/
		void ptimer_set_period(ptimer_state *s, int64_t period);

		/**
		* ptimer_set_freq - Set counter frequency in Hz
		* @s: ptimer to configure
		* @freq: counter frequency in Hz
		*
		* This does the same thing as ptimer_set_period(), so you only
		* need to call one of them. If the counter behaviour is specified
		* as setting the frequency then this function is more appropriate,
		* because it allows specifying an effective period which is
		* precise to fractions of a nanosecond, avoiding rounding errors.
		*/
		void ptimer_set_freq(ptimer_state *s, uint32_t freq);

		/**
		* ptimer_get_limit - Get the configured limit of the ptimer
		* @s: ptimer to query
		*
		* This function returns the current limit (reload) value
		* of the down-counter; that is, the value which it will be
		* reset to when it hits zero.
		*
		* Generally timer devices using ptimers should be able to keep
		* their reload register state inside the ptimer using the get
		* and set limit functions rather than needing to also track it
		* in their own state structure.
		*/
		uint64_t ptimer_get_limit(ptimer_state *s);

		/**
		* ptimer_set_limit - Set the limit of the ptimer
		* @s: ptimer
		* @limit: initial countdown value
		* @reload: if nonzero, then reset the counter to the new limit
		*
		* Set the limit value of the down-counter. The @reload flag can
		* be used to emulate the behaviour of timers which immediately
		* reload the counter when their reload register is written to.
		*/
		void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload);

		/**
		* ptimer_get_count - Get the current value of the ptimer
		* @s: ptimer
		*
		* Return the current value of the down-counter. This will
		* return the correct value whether the counter is enabled or
		* disabled.
		*/
		uint64_t ptimer_get_count(ptimer_state *s);

		/**
		* ptimer_set_count - Set the current value of the ptimer
		* @s: ptimer
		* @count: count value to set
		*
		* Set the value of the down-counter. If the counter is currently
		* enabled this will arrange for a timer callback at the appropriate
		* point in the future.
		*/
		void ptimer_set_count(ptimer_state *s, uint64_t count);

		/**
		* ptimer_run - Start a ptimer counting
		* @s: ptimer
		* @oneshot: non-zero if this timer should only count down once
		*
		* Start a ptimer counting down; when it reaches zero the bottom half
		* passed to ptimer_init() will be invoked. If the @oneshot argument is zero,
		* the counter value will then be reloaded from the limit and it will
		* start counting down again. If @oneshot is non-zero, then the counter
		* will disable itself when it reaches zero.
		*/
		void ptimer_run(ptimer_state *s, int oneshot);

		/**
		* ptimer_stop - Stop a ptimer counting
		* @s: ptimer
		*
		* Pause a timer (the count stays at its current value until ptimer_run()
		* is called to start it counting again).
		*
		* Note that this can cause it to "lose" time, even if it is immediately
		* restarted.
		*/
		void ptimer_stop(ptimer_state *s);

		extern const VMStateDescription vmstate_ptimer;