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[media] dvb: document dvb_frontend_sleep_until()
This function is used mainly at the DVB core, in order to provide emulation for a legacy ioctl. The only current exception is the stv0299 driver, with takes more than 8ms to switch voltage, breaking the emulation for FE_DISHNETWORK_SEND_LEGACY_CMD. Document that. Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
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@ -891,10 +891,11 @@ static void dvb_frontend_stop(struct dvb_frontend *fe)
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}
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/*
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* Sleep until gettimeofday() > waketime + add_usec
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* This needs to be as precise as possible, but as the delay is
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* usually between 2ms and 32ms, it is done using a scheduled msleep
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* followed by usleep (normally a busy-wait loop) for the remainder
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* Sleep for the amount of time given by add_usec parameter
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*
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* This needs to be as precise as possible, as it affects the detection of
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* the dish tone command at the satellite subsystem. The precision is improved
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* by using a scheduled msleep followed by udelay for the remainder.
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*/
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void dvb_frontend_sleep_until(ktime_t *waketime, u32 add_usec)
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{
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@ -404,6 +404,11 @@ struct dtv_frontend_properties;
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* FE_ENABLE_HIGH_LNB_VOLTAGE ioctl (only Satellite).
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* @dishnetwork_send_legacy_command: callback function to implement the
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* FE_DISHNETWORK_SEND_LEGACY_CMD ioctl (only Satellite).
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* Drivers should not use this, except when the DVB
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* core emulation fails to provide proper support (e.g.
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* if set_voltage() takes more than 8ms to work), and
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* when backward compatibility with this legacy API is
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* required.
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* @i2c_gate_ctrl: controls the I2C gate. Newer drivers should use I2C
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* mux support instead.
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* @ts_bus_ctrl: callback function used to take control of the TS bus.
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@ -693,6 +698,29 @@ extern void dvb_frontend_reinitialise(struct dvb_frontend *fe);
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extern int dvb_frontend_suspend(struct dvb_frontend *fe);
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extern int dvb_frontend_resume(struct dvb_frontend *fe);
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extern void dvb_frontend_sleep_until(ktime_t *waketime, u32 add_usec);
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/**
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* dvb_frontend_sleep_until() - Sleep for the amount of time given by
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* add_usec parameter
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*
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* @waketime: pointer to a struct ktime_t
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* @add_usec: time to sleep, in microseconds
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*
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* This function is used to measure the time required for the
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* %FE_DISHNETWORK_SEND_LEGACY_CMD ioctl to work. It needs to be as precise
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* as possible, as it affects the detection of the dish tone command at the
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* satellite subsystem.
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*
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* Its used internally by the DVB frontend core, in order to emulate
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* %FE_DISHNETWORK_SEND_LEGACY_CMD using the &dvb_frontend_ops.set_voltage()
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* callback.
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*
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* NOTE: it should not be used at the drivers, as the emulation for the
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* legacy callback is provided by the Kernel. The only situation where this
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* should be at the drivers is when there are some bugs at the hardware that
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* would prevent the core emulation to work. On such cases, the driver would
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* be writing a &dvb_frontend_ops.dishnetwork_send_legacy_command() and
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* calling this function directly.
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*/
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void dvb_frontend_sleep_until(ktime_t *waketime, u32 add_usec);
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#endif
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