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Tue, 6 Oct 2026 08:34:06 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: ApDcdGHCsDIN Date: Tue, 06 Oct 2026 14:33:36 +0200 From: "Arnd Bergmann" To: "Alexandre Belloni" Cc: "Karl Mehltretter" , linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org Message-Id: In-Reply-To: <202610051349454ed35b56@mail.local> References: <20260914212537.1452-1-kmehltretter@gmail.com> <7c020979-cf03-4ece-a7d4-b1475d1400c3@app.fastmail.com> <59ba6707-c5d5-4fd8-9200-f910e61d9232@app.fastmail.com> <5515c266-f9cd-405f-b7a8-1ec45d9d902a@app.fastmail.com> <202609222137059e745547@mail.local> <202610051349454ed35b56@mail.local> Subject: Re: [PATCH] rtc: class: Make the time32 hctosys limit configurable Content-Type: text/plain Content-Transfer-Encoding: 7bit On Mon, Oct 5, 2026, at 15:49, Alexandre Belloni wrote: > On 24/09/2026 17:07:30+0200, Arnd Bergmann wrote: >> On Tue, Sep 22, 2026, at 23:37, Alexandre Belloni wrote: >> >> Not sure what exactly you are suggesting here. Do you mean we should >> try again to address this in systemd in order to no longer need >> the RTC_HCTOSYS hack? >> > > Well I guess we'll get the same answer that this is too late in the boot > process. Right > My proposed solution is to have a way to tell the kernel what size of > time_t userspace actually supports as there is no way to automatically > detect it. That's why I was thinking a kernel cmdline parameter would > fit. This would allow us to be 100% correct. > > Else, I'm fine with your last proposal. Ok, thanks! A command line argument would work for me as well, if we can make it have a working default for the COMPAT_32BIT_TIME=n case. We could of course combine a compile-time and boot-time flag, but there should not be any need for that. > I guess this would leave us with > two unhandled cases: > - 64bit systems with 32 bit userspace that you said we don't want to > support Right, as far as I'm concerned this has always done what I want, so no need to change it. > - 32bit systems with 64bit time_t userspace that would not work > properly with the default configuration. At this point it's just part of the platform defconfig, and users can pick the setting. Arnd