Re: [Qemu-devel] How does QEMU kernel receive any input events from host OS

[Amey Moghe <amey1288@gmail.com>]

Hello,

Thanks for the details.I understood how any input event is processed.
But if I pressed a key in guest OS environment then how does client
i.e. guest OS ( with reference to VNC server )   come to know that it
has to send key_event to VNC server? Does client through qemu,
recognise it either from X server running on host OS (e.g. linux ) or
directly from host OS's kernel ?


Thanks,
Amey.

On 9/3/09, David Turner <digit@google.com> wrote:
> the QEMU frontend (e.g. the VNC server or the SDL window) is in charge of
> translating user events
> into emulated hardware ones. Most generally, this will mean emulating a
> keyboard or mouse IRQ
> and the associated i/o protocol. Exact details depend on which hardware you
> want to emulate.
>
> For example, when emulating a PC with PS/2 keyboard and mouse, the code in
> hw/ps2.c will be used.
>
> Here's a concrete example:
>
>    - The VNC server receives packets from the client (see
>    protocol_client_msg in vnc.c).
>    Some of them correspond to keyboard events (processed in key_event() in
>    the same file),
>    which end up calling kbd_put_keycode() after translating the VNC
>    keycode/state into
>    a different key scancode.
>
>
>    - kbd_put_keycode() is defined in vl.c and calls the hardware-specific
>    keycode translator.
>
>
>    - For PC emulation, this happens to be ps2_put_keycode() defined in
>    hw/ps2.c, and
>    registered at startup by ps2_kbd_init() in the same file. It probably is
>    a different function
>    for different emulated hardware.
>
>
>    - The implementation of ps2_put_keycode() will end up enqueue-ing a
>    keycode into
>    a queue then raising an IRQ.
>
>    - The guest kernel responds to the IRQ by running its keyboard driver
>    code, the latter
>    will try to read data from the PS/2 queue
>
>
> The SDL front-end receives user events differently, but still ends up
> calling kbd_put_keycode().
> Same thing happens for mouse events, and about anything that needs to
> emulate hardware
> (e.g. serial/usb/bluetooth/etc...) but implementations and specifics may
> differ.
>
> Hope this helps
>
> On Wed, Sep 2, 2009 at 5:55 AM, Amey Moghe <amey1288@gmail.com> wrote:
>
>> Hello all,
>>
>> I am new to QEMU.While reading about qemu , I came across one statement:
>> "QEMU does not depend on the presence of graphical output methods on the
>> host system. Instead, it allows one to access the screen of the guest OS
>> via
>> VNC. It can also use an emulated serial line, without any screen, with
>> applicable operating systems." on following link :
>>
>> http://en.wikipedia.org/wiki/QEMU
>>
>> So please can anybodys tell me how does qemu use VNC server for receiving
>> events and if yes then how does it receive events from host OS? Or is
>> there
>> any other way with which QEMU receives input events from host OS?
>