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Re: [PATCH 3/6] y2038: Introduce struct __timeval64 - new internal glibc type
- From: Arnd Bergmann <arnd at arndb dot de>
- To: Alistair Francis <alistair23 at gmail dot com>
- Cc: Lukasz Majewski <lukma at denx dot de>, Joseph Myers <joseph at codesourcery dot com>, Paul Eggert <eggert at cs dot ucla dot edu>, Adhemerval Zanella <adhemerval dot zanella at linaro dot org>, Samuel Thibault <samuel dot thibault at ens-lyon dot org>, Alistair Francis <alistair dot francis at wdc dot com>, GNU C Library <libc-alpha at sourceware dot org>, Siddhesh Poyarekar <siddhesh at gotplt dot org>, Florian Weimer <fweimer at redhat dot com>, Florian Weimer <fw at deneb dot enyo dot de>, Zack Weinberg <zackw at panix dot com>, "Carlos O'Donell" <carlos at redhat dot com>, Andreas Schwab <schwab at suse dot de>
- Date: Sun, 19 Jan 2020 12:36:36 +0100
- Subject: Re: [PATCH 3/6] y2038: Introduce struct __timeval64 - new internal glibc type
- References: <20200118072047.23071-1-lukma@denx.de> <20200118072047.23071-4-lukma@denx.de> <CAKmqyKPD=_3LZ+YBEn53ZuoPo0hq_vdAFTMHdmPwo5Q795Wekw@mail.gmail.com>
On Sat, Jan 18, 2020 at 11:48 PM Alistair Francis <alistair23@gmail.com> wrote:
>
> On Sat, Jan 18, 2020 at 5:21 PM Lukasz Majewski <lukma@denx.de> wrote:
> >
> > This type is a glibc's "internal" type similar to struct timeval but
> > whose tv_sec field is a __time64_t rather than a time_t, which makes it
> > Y2038-proof. This struct is NOT supposed to be passed to the kernel -
> > instead it shall be converted to struct __timespec64 and clock_[sg]ettime
> > syscalls shall be used (which are now Y2038 safe).
> >
> > Build tests:
> > ./src/scripts/build-many-glibcs.py glibcs
>
> Looks good, I have the same thing in my tree :)
I think it's slightly different: __suseconds_t on rv32 is 64 bit wide, while
on all existing 32-bit architectures as well as sparc64 it is 32-bit wide.
While almost all kernel interfaces based on timeval have been replaced
by those based on timespec, there are a small number that need this
to be compatible with the kernel's layout, or to have an explicit conversion:
- Socket timestamps with SO_TIMESTAMP
- Socket timeouts with SO_RCVTIMEO/SO_SNDTIMEO
- pc-style parallel ports with the PPGETTIME/PPSETTIME ioctls
- video4linux with the VIDIOC_QUERYBUF/VIDIOC_QBUF/VIDIOC_DQBUF
VIDIOC_PREPARE_BUF and VIDIOC_OMAP3ISP_STAT_REQ ioctls
Arnd