linux-kernel - Re: [PATCH] rtc: class: support hctosys from modular RTC drivers

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Message-ID: <b96f085b-8a0c-7c71-4fde-8af83d49823a@google.com>
Date:   Wed, 6 Nov 2019 15:37:49 -0800
From:   Steve Muckle <smuckle@...gle.com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Alessandro Zummo <a.zummo@...ertech.it>,
        linux-kernel@...r.kernel.org, linux-rtc@...r.kernel.org,
        kernel-team@...roid.com
Subject: Re: [PATCH] rtc: class: support hctosys from modular RTC drivers

On 11/6/19 3:19 PM, Alexandre Belloni wrote:
> On 06/11/2019 11:46:25-0800, Steve Muckle wrote:
>> Due to distribution constraints it may not be possible to statically
>> compile the required RTC driver into the kernel.
>>
>> Expand RTC_HCTOSYS support to cover all RTC devices (statically compiled
>> or not) by checking at the end of RTC device registration whether the
>> time should be synced.
>>
> 
> This does not really help distributions because most of them will still
> have "rtc0" hardcoded and rtc0 is often the rtc that shouldn't be used.

Just for my own edification, why is that? Is rtc0 normally useless on PC 
for some reason?

On the platforms I'm working with I believe it can be assured that rtc0 
will be the correct rtc. That doesn't help typical distributions though.

What about a kernel parameter to optionally override the rtc hctosys 
device at runtime?

> Can't you move away from HCTOSYS and do the correct thing in userspace
> instead of the crap hctosys is doing?

Yes, I just figured it's a small change, and if hctosys can be made to 
work might as well use that.