On Thu, Oct 27, 2016 at 03:24:55PM -0700, Deepa Dinamani wrote: > On Wed, Oct 26, 2016 at 7:56 PM, Peter Hutterer > <peter.hutterer@xxxxxxxxx> wrote: > > On Mon, Oct 17, 2016 at 08:27:32PM -0700, Deepa Dinamani wrote: > >> struct timeval is not y2038 safe. > >> All usage of timeval in the kernel will be replaced by > >> y2038 safe structures. > >> > >> struct input_event maintains time for each input event. > >> Real time timestamps are not ideal for input as this > >> time can go backwards as noted in the patch a80b83b7b8 > >> by John Stultz. Hence, having the input_event.time fields > >> only big enough for monotonic and boot times are > >> sufficient. > >> > >> Leave the original input_event as is. This is to maintain > >> backward compatibility with existing userspace interfaces > >> that use input_event. > >> Introduce a new replacement struct raw_input_event. > > > > general comment here - please don't name it "raw_input_event". > > First, when you grep for input_event you want the new ones to show up too, > > so a struct input_event_raw would be better here. That also has better > > namespacing in general. Second though: the event isn't any more "raw" than > > the previous we had. > > > > I can't think of anything better than struct input_event_v2 though. > > The general idea was to leave the original struct input_event as a > common interface for userspace (as it cannot be deleted). > So reading raw data unformatted by the userspace will have the new > struct raw_input_event format. > This was the reason for the "raw" in the name. > > struct input_event_v2 is fine too, if this is more preferred. > > >> This replaces timeval with struct input_timeval. This structure > >> maintains time in __kernel_ulong_t or compat_ulong_t to allow > >> for architectures to override types as in the case of x32. > >> > >> The change requires any userspace utilities reading or writing > >> from event nodes to update their reading format to match > >> raw_input_event. The changes to the popular libraries will be > >> posted along with the kernel changes. > >> The driver version is also updated to reflect the change in > >> event format. > > > > Doesn't this break *all* of userspace then? I don't see anything to > > negotiate the type of input event the kernel gives me. And nothing right now > > checks for EVDEV_VERSION, so they all just assume it's a struct > > input_event. Best case, if the available events aren't a multiple of > > sizeof(struct input_event) userspace will bomb out, but unless that happens, > > everyone will just happily read old-style events. > > > > So we need some negotiation what is acceptable. Which also needs to address > > the race conditions we're going to get when events start coming in before > > the client has announced that it supports the new-style events. > > No, this does not break any userspace right now. > Both struct input_event and struct raw_input_event are exactly the same today. oh, right, the ABI is the same. I see that now, thanks. > This will be the case until a 2038-safe glibc is used with a 64 bit time_t flag. > > So these are the scenarios: > 1. old kernel driver + new userspace > -- should still be ok until 2038. Version checks could help discover these > 2. new kernel driver + old userspace (without recompiled with new 2038 gblic) > -- works because the format is really the same. > > The patch I posted to libevdev checks this driver version. btw, where did you post the libevdev patch? I haven't seen it anywhere I'm subscribed to. > And, hence any library that results in a call to libevdev_set_fd() > will fail if it is not this updated driver. without having seen the libevdev patch - that sounds like a bad idea . there are plenty of usecases where libevdev_set_fd() is called but timestamps in events just don't matter. So we may need need some more negotiation between the library user, libevdev and the kernel. Cheers, Peter > We could just do a similar check in every library also. > I think the latter would be better. > > So, the kernel patches can go in as a no-op right now and then I can > add version checks to respective user space libraries. -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
