[RFC] generic MIPS RTC driver

Maciej W. Rozycki macro at ds2.pg.gda.pl
Tue Nov 13 05:55:37 EST 2001

On Mon, 12 Nov 2001, Jun Sun wrote:

> The /dev/rtc interface is highly influenced by MC146818 chip, which not all
> RTC devices are alike.  The only fundamental thing in the driver is really the
> read and write time.

 You need only to keep the interface, which is:

static struct file_operations rtc_fops = {
	owner:		THIS_MODULE,
	llseek:		no_llseek,
	read:		rtc_read,
	poll:		rtc_poll,
	ioctl:		rtc_ioctl,
	open:		rtc_open,
	release:	rtc_release,
	fasync:		rtc_fasync,

Of these you probably must only implement open() and ioctl() -- you may
provide others as hardware permits -- see how these functions are
implemented in drivers/char/rtc.c.  The interface is pretty generic, IMHO.

> If their abstraction is reasonable, perhaps they can all converge to a better,
> more generic rtc interface.

 Just implement the ioctls given hardware permits and return -EINVAL for
others.  Again, they are pretty generic: get/set the time, alarm, epoch,
disable/enable various interrupts, etc. -- see include/linux/rtc.h.  You
may propose additional ioctls if they would be useful for particular

+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+        e-mail: macro at ds2.pg.gda.pl, PGP key available        +

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