Real Time Clock

[Joel Sherrill]

Thomas Doerfler wrote:
> Hi,
>
> I think it makes sense to convert the rtc access functions to
> standardized "*_read" and "*_write" functions in the classic API driver
> IF (instead of dedicated functions).
>
>   
That makes sense.  stat( "/dev/rtc" ) to get  the major/minor?
> It may surely make sense to map the POSIX timer functions to that device.
>
>   
yes.  But remember clockid_t is shared by the clock_[sg]ettime
methods and so those would have to be covered.
> Any further comments?
>
>   
What GNU/Linux lets a user do?  How do you write a program
there to access the RTC?  What does the program hwclock
do?

We will need a shell method similar to hwclock and it would
be best to be able to port the BSD equivalent of that to the
RTEMS Shell environment.  Chris has already ported other
BSD methods.  This would require the API to be REALLY standard.  :)

FYI psim on the head supports an RTC device. 

--joel
> wkr,
> Thomas.
>
> Sebastian Huber wrote:
>   
>> Hi,
>>
>> in order to support the POSIX clock_gettime(), clock_settime() and
>> clock_getres() functions we need a RTC driver interface which can at least read
>>  and set the RTC.  An interface proposal follows:
>>
>> /**
>>  * @file
>>  *
>>  * Real-time clock driver interface.
>>  */
>>
>> /*
>>  *  COPYRIGHT (c) 1989-2001.
>>  *  On-Line Applications Research Corporation (OAR).
>>  *
>>  *  The license and distribution terms for this file may be
>>  *  found in the file LICENSE in this distribution or at
>>  *  http://www.rtems.com/license/LICENSE.
>>  *
>>  *  $Id: rtc.h,v 1.4 2005/01/28 08:04:27 ralf Exp $
>>  */
>>
>> #ifndef _RTEMS_RTC_H
>> #define _RTEMS_RTC_H
>>
>> #include <rtems.h>
>>
>> #ifdef __cplusplus
>> extern "C" {
>> #endif
>>
>> /**
>>  * @defgroup rtems_rtc Real-Time Clock Driver Interface
>>  *
>>  * This driver interface provides support to read and set the real-time clock
>>  * and to initialize the time of day for the system.
>>  *
>>  * @{
>>  */
>>
>> /**
>>  * Device file name path.
>>  */
>> #define RTC_DEVICE_NAME "/dev/rtc"
>>
>> /**
>>  * Device driver table entry.
>>  */
>> #define RTC_DRIVER_TABLE_ENTRY \
>>   { rtc_initialize, rtc_open, rtc_close, \
>>     rtc_read, rtc_write, rtc_control }
>>
>> /**
>>  * Initializes the real-time clock device and sets the time of day for the
>>  * system.
>>  *
>>  * If the real-time clock provides an invalid time of day value the system time
>>  * of day must remain untouched.
>>  */
>> rtems_device_driver rtc_initialize(
>>   rtems_device_major_number,
>>   rtems_device_minor_number,
>>   void *
>> );
>>
>> /**
>>  * Opens the real-time clock device.
>>  */
>> rtems_device_driver rtc_open(
>>   rtems_device_major_number,
>>   rtems_device_minor_number,
>>   void *
>> );
>>
>> /**
>>  * Closes the real-time clock device.
>>  */
>> rtems_device_driver rtc_close(
>>   rtems_device_major_number,
>>   rtems_device_minor_number,
>>   void *
>> );
>>
>> /**
>>  * Reads the real-time clock value.
>>  *
>>  * The value will be returned in a @ref rtems_time_of_day structure.
>>  */
>> rtems_device_driver rtc_read(
>>   rtems_device_major_number,
>>   rtems_device_minor_number,
>>   void *
>> );
>>
>> /**
>>  * Sets the real-time clock value.
>>  *
>>  * The value will be set from a @ref rtems_time_of_day structure.
>>  */
>> rtems_device_driver rtc_write(
>>   rtems_device_major_number,
>>   rtems_device_minor_number,
>>   void *
>> );
>>
>> /**
>>  * Controls the real-time clock.
>>  */
>> rtems_device_driver rtc_control(
>>   rtems_device_major_number,
>>   rtems_device_minor_number,
>>   void *
>> );
>>
>> /** @} */
>>
>> #ifdef __cplusplus
>> }
>> #endif
>>
>> #endif
>>
>>     
>
>
>   


-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel.sherrill at OARcorp.com        On-Line Applications Research
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