On Fri, 7 Apr 2017 14:04:40 +1000 Peter Hutterer <[email protected]> wrote:
> For the initial patchset, see > https://lists.freedesktop.org/archives/wayland-devel/2017-March/033626.html > For a high-level description, see > http://who-t.blogspot.com.au/2017/04/inputfd-protocol-for-direct-access-to.html > > This is a relatively unexciting update, the notable bits are: > * instead of having a per-device type get_seat_* request, we now have just a > basic get_seat() request that returns all inputfd-capable devices. This > allows for mice, keyboards, etc as well without having more requests > * the property description has a link to the github repo i started for the > dictionary > * the fd was split into a read/write fd to allow for pipes, the type was > extended for an evdev-protocol-carrying pipe. (I'm not convinced this > is good enough yet, just as a note) Hi, I don't understand the need for two fds. Yes, pipes are one-directional, but one could use a AF_UNIX socket for bidirectional comms (socketpair(2)). Having a second pipe fd for writing does not allow for a synchronous command a la ioctl() anyway. You have read and write fds in the same event. Wayland is incapable of sending an argument of type fd that is not actually a real open file descriptor. This means that if the write fd is not needed, one still needs to create a valid open fd, send it, and close it. Even if you send the same fd in both arguments, the receiver will receive two different valued fds. Determining if they are the same underlying "file" is... I don't actually know how to do that. Something about comparing fstat(2) information. We had the problem with the linux_dmabuf protocol, where one needs to send a variable number of fds. We solved it by sending one event per fd. > > This addresses some of the immediate comments. The big list of TODO is: > * LED control, force feedback, and other write-back channels that don't work > on the fd but go through sysfs > * battery status and other notifications Thanks, pq
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