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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Fri, 10 Jan 2020 22:19:01 +0100
Message-ID: <CAK8P3a2VONV2Z6rs=xpntJyzfX4W7YijqCFr-f-PNMm3g4zRyA@mail.gmail.com>
Subject: Re: [PATCH] hcidump: add support for time64 based libc
To:     Rich Felker <dalias@libc.org>
Cc:     Bluez mailing list <linux-bluetooth@vger.kernel.org>,
        y2038 Mailman List <y2038@lists.linaro.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Deepa Dinamani <deepa.kernel@gmail.com>,
        Guy Harris <guy@alum.mit.edu>
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On Fri, Jan 10, 2020 at 10:05 PM Rich Felker <dalias@libc.org> wrote:
>
> On Fri, Jan 10, 2020 at 09:49:03PM +0100, Arnd Bergmann wrote:
> > musl is moving to a default of 64-bit time_t on all architectures,
> > glibc will follow later. This breaks reading timestamps through cmsg
> > data with the HCI_TIME_STAMP socket option.
> >
> > Change both copies of hcidump to work on all architectures.  This also
> > fixes x32, which has never worked, and carefully avoids breaking sparc64,
> > which is another special case.
>
> Won't it be broken on rv32 though? Based on my (albeit perhaps
> incomplete) reading of the thread, I think use of HCI_TIME_STAMP
> should just be dropped entirely in favor of using SO_TIMESTAMPNS -- my
> understanding was that it works with bluetooth sockets too.

All 32-bit architectures use old_timeval32 timestamps in the kernel
here, even rv32 and x32. As a rule, we keep the types bug-for-bug
compatible between architectures and fix them all at the same time.

Changing hcidump to SO_TIMESTAMPNS would work as well, but
that is a much bigger change and I don't know how to test that.

     Arnd