Re: RFC: Counter driver API


Tseng, Kuo-Lang <kuo-lang.tseng@...>
 

Since this RFC has been quietly for a while and it seems we have reached
a good amount of feedback so we will implement it and update the current
patch.

-----Original Message-----
From: Tseng, Kuo-Lang [mailto:kuo-lang.tseng(a)intel.com]
Sent: Thursday, March 03, 2016 5:45 PM
To: Guedes, Andre <andre.guedes(a)intel.com>; Sanchez-Palencia, Jesus
<jesus.sanchez-palencia(a)intel.com>; Tomasz Bursztyka
<tomasz.bursztyka(a)linux.intel.com>
Cc: devel(a)lists.zephyrproject.org
Subject: [devel] Re: Re: Re: Re: Re: RFC: Counter driver API

Hi Andre, Tomasz, Jesus,

Thanks for your feedbacks. I updated the API with these feedbacks. Please correct
or if I missed any part that needed to be reflected. The updated API looks like
below:

/**
* Start the counter device. If the device is a 'count up' counter the
* counter initial value is set to zero. If it is a 'countdown' counter
* the initial value is set to the maximum value supported by the device.
*
* @brief Start counter device in free running mode.
* @param dev Pointer to the device structure for the driver instance.
* @retval DEV_OK If successful.
* @retval DEV_* Code otherwise.
*/
int counter_start(struct device *dev);

/**
* @brief Stop counter device. If alarm was set, this function also clears
* the alarm setting.
* @param dev Pointer to the device structure for the driver instance.
*
* @retval DEV_OK If successful.
* @retval DEV_NO_SUPPORT if the device doesn't support stopping the
* counter (e.g. free running counters).
*/
int counter_stop(struct device *dev);

/**
* @brief Read current counter value
* @param dev Pointer to the device structure for the driver instance.
*
* @return 32-bit value
*/
uint32_t counter_read(struct device *dev);

/**
* Set an alarm.
*
* @brief Set an alarm.
* @param dev Pointer to the device structure for the driver instance.
* @param callback Pointer to the callback function. If this is NULL, this function
* unsets the alarm.
* @param count Number of counter ticks.
* @param user_data pointer to user data
*
* @retval DEV_OK If successful.
* @retval DEV_INVALID_OP If the counter was not started yet.
* @retval DEV_NO_SUPPORT if the device doesn't support interrupt (e.g.
* free running counters).
*/
int counter_set_alarm(struct device *dev, counter_callback_t callback, uint32_t
count, void *user_data);

typedef void (*counter_callback_t)(struct device *dev, void *user_data)



-----Original Message-----
From: Andre Guedes [mailto:andre.guedes(a)intel.com]
Sent: Thursday, March 03, 2016 6:22 AM
To: Sanchez-Palencia, Jesus <jesus.sanchez-palencia(a)intel.com>; Tomasz
Bursztyka <tomasz.bursztyka(a)linux.intel.com>
Cc: devel(a)lists.zephyrproject.org
Subject: [devel] Re: Re: Re: Re: RFC: Counter driver API

Hi Jesus,

Quoting Jesus Sanchez-Palencia (2016-03-03 09:52:43)
/**
* Start the counter device. If the device is a 'count up' counter the
* counter initial value is set to zero. It it is a 'countdown' counter
* the initial value is set to the maximum value supported by the device.
*
* @brief Start counter device.
* @param dev Pointer to the device structure for the driver instance.
* @retval DEV_OK If successful.
* @retval DEV_* Code otherwise.
Probably better here to:
@retval DEV_NO_SUPPORT if the device doesn't support starting the
counter (e.g. free running counters).
I don't think DEV_NO_SUPPORT will be ever returned by the
counter_start API since this is a very basic API and all counter must support it.

Anyways, I think we should list in the documentation all the return
codes a given API can return instead of simply saying DEV_*.

Looks like we are moving to Posix error codes, so it would be wise
to do it here as well. (better now than after the API is upstream).
Apply that to all.
It's still not clear if the change will go straight to Posix errors
or if the transition through DEV_* will happen first. We can't mix both.
+1.

/**
* Set an alarm callback. If the counter was not started yet, this
* function starts and set the alarm.
Set an alarm callback. If the counter was not started yet, this
will do it automatically (no need to call counter_start()).

In general having an API that does 2 things is not a good idea.
An API called 'counter_set_alarm' should do only that, IMO. I'd
rather have
2 API calls for that (set and start), but if we really want it to do
both, then maybe better calling it counter_init_alarm(..., int count); ?!
I'm fine with we have 2 API calls (counter_start and counter_set_alarm).

Regards,

Andre

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