linux-kernel - Re: RTC_DRV_CMOS can break userspace interface

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Message-ID: <20070531043229.GA30888@dose.home.local>
Date:	Thu, 31 May 2007 06:32:29 +0200
From:	Tino Keitel <tino.keitel@....de>
To:	Linux Kernel list <linux-kernel@...r.kernel.org>
Subject: Re: RTC_DRV_CMOS can break userspace interface

On Mon, May 28, 2007 at 14:06:52 -0700, David Brownell wrote:

[...]

> That seems to be true.  And those particular users should learn the
> portable /sys/class/rtc/rtc0/wakealarm syntax ... e.g. using numeric
> seconds-since-epoch ("date '+%s'") instead of strings the kernel needs
> to parse.  That way, they can start converting usage sooner.

Hi,

I use /proc/acpi/alarm a lot and tried to learn how to use
/sys/class/rtc/rtc0/wakealarm. However, I have no /sys/class/rtc/rtc0
until I load the rtc-test driver. I tried all RTC drivers that are
available in 2.6.21, without success:

$ grep RTC /boot/config-2.6.21
CONFIG_RTC=y
# CONFIG_HPET_RTC_IRQ is not set
# CONFIG_SND_RTCTIMER is not set
CONFIG_RTC_LIB=y
CONFIG_RTC_CLASS=y
CONFIG_RTC_HCTOSYS=y
CONFIG_RTC_HCTOSYS_DEVICE="rtc0"
# CONFIG_RTC_DEBUG is not set
# RTC interfaces
CONFIG_RTC_INTF_SYSFS=y
# CONFIG_RTC_INTF_PROC is not set
CONFIG_RTC_INTF_DEV=y
# CONFIG_RTC_INTF_DEV_UIE_EMUL is not set
# RTC drivers
CONFIG_RTC_DRV_CMOS=y
CONFIG_RTC_DRV_DS1553=m
CONFIG_RTC_DRV_DS1742=m
CONFIG_RTC_DRV_M48T86=m
CONFIG_RTC_DRV_TEST=m
CONFIG_RTC_DRV_V3020=m

In dmesg, I see these messages from RTC_DRV_CMOS:

rtc_cmos 00:09: rtc core: registered rtc_cmos as rtc0
rtc_cmos: probe of 00:09 failed with error -16
drivers/rtc/hctosys.c: unable to open rtc device (rtc0)

So all I can do is to continue to use /proc/acpi/alarm.

Regards,
Tino
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