Re: [Question: Drivers/input/evdev.c] What is the use of write function in evdev_fops?

On Fri, Aug 15, 2014 at 02:01:48AM +0530, Aniroop Mathur wrote:
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2 separate file descriptors like below ?
int fd1 = open("/dev/uinput", O_RDWR);
int fd2 = open("/dev/uinput", O_RDWR);

But my reading data will still come in struct input_event as mentioned
above.
It has only time, type, code and value.
So, how we can use bitmask here ?

struct input_event {
struct timeval time;
__u16 type;
__u16 code;
__s32 value;
};

By opening 2 fds you'll end up creating 2 separate input devices with separate evdev nodes, etc, so you will not mix up input events.

I think at this time you should just try actually using uinput and that should clear things for you.

Can you please explain what do you mean by separate evdev nodes ?
Do you mean two separate evdev nodes for uinput ?
But as we discussed before, there is only one node in case of uinput
i.e. /dev/uinput.

Uinput allows to creating input devices driven from userspace. You can
create as many separate input devices as you want by opening
/dev/uinput several times since it creates a device per file descriptor.
Each of these input devices will get evdev attached to it and will get
it's own /dev/input/eventX node created.

Really, please try using uinput, it will clear a lot if things for you.
For example, see what http://www.freedesktop.org/wiki/Evemu/ does.

Thank you Mr. Torokhov for the discussion and answering my queries. :)
I will try to explore more.

I recommend you look at libevdev if you're planning to use uinput. evemu
uses that now too and it makes a whole bunch of stuff easier and less likely
to go wrong.
http://freedesktop.org/wiki/Software/libevdev/

specifically:
http://www.freedesktop.org/software/libevdev/doc/1.2/group__uinput.html

Cheers,
   Peter