asynchronous resolution change

asynchronous resolution change

[Jatin Kumar]

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Hi,

I am new to linux fb model and had some queries regarding resolution change
mechanisms.

Consider a situation where the frambuffer kernel module (vfb/xenfb etc)
wants to change the resolution.

1. Is there a mechanism to this, considering the applications/windowing
system/console above the framebuffer hasnt initiated the size change?

2. Is there a way to do an upcall into the application/windowing
system/console modules to inform them about the size change asynchronously?

In this particular case ; the display hardware(instead of the user) has
initiated the resolution change.Is it possible in the current fb framework
to support it?

Excuse me for the lack of knowledge in this area.
Any other suggstions/explanations are welcome.

Thanks
jk

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Re: asynchronous resolution change

[Geert Uytterhoeven]

On Tue, 18 Nov 2008, Jatin Kumar wrote:
> I am new to linux fb model and had some queries regarding resolution change
> mechanisms.
> 
> Consider a situation where the frambuffer kernel module (vfb/xenfb etc)
> wants to change the resolution.
> 
> 1. Is there a mechanism to this, considering the applications/windowing
> system/console above the framebuffer hasnt initiated the size change?
> 
> 2. Is there a way to do an upcall into the application/windowing
> system/console modules to inform them about the size change asynchronously?
> 
> In this particular case ; the display hardware(instead of the user) has
> initiated the resolution change.Is it possible in the current fb framework
> to support it?

Yes there is! If the resolution is changed, and the number of columns and
lines of the console changes, the tty subsystem will send the SIGWINCH signal
to the application, cfr. tty_do_resize() in drivers/char/tty_io.c.

Note that not all applications handle it. E.g. X doesn't, AFAIK.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

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Re: asynchronous resolution change

[Jatin Kumar]

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On Wed, Nov 19, 2008 at 3:35 AM, Geert Uytterhoeven <geert@linux-m68k.org>wrote:

> On Tue, 18 Nov 2008, Jatin Kumar wrote:
> > I am new to linux fb model and had some queries regarding resolution
> change
> > mechanisms.
> >
> > Consider a situation where the frambuffer kernel module (vfb/xenfb etc)
> > wants to change the resolution.
> >
> > 1. Is there a mechanism to this, considering the applications/windowing
> > system/console above the framebuffer hasnt initiated the size change?
> >
> > 2. Is there a way to do an upcall into the application/windowing
> > system/console modules to inform them about the size change
> asynchronously?
> >
> > In this particular case ; the display hardware(instead of the user) has
> > initiated the resolution change.Is it possible in the current fb
> framework
> > to support it?
>
> Yes there is! If the resolution is changed, and the number of columns and
> lines of the console changes, the tty subsystem will send the SIGWINCH
> signal
> to the application, cfr. tty_do_resize() in drivers/char/tty_io.c.
>
> Note that not all applications handle it. E.g. X doesn't, AFAIK.
>
> Gr{oetje,eeting}s,
>
>                                                Geert



Hi Geert,

Thanks much for the info.

Is the tty_io_resize( ) relatively new? .
I am looking at 2.6.18.8 src code (used for xen) and could not find the
function.

Also are there any plans for exposing a similar callback api in the linux fb
model to make the applications stay updated about the underlying
resolution/hardware mode changes?

Thanks so much,
Jatin


>
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 --
> geert@linux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker.
> But
> when I'm talking to journalists I just say "programmer" or something like
> that.
>                                                            -- Linus
> Torvalds
>

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Re: asynchronous resolution change

[Geert Uytterhoeven]

On Mon, 24 Nov 2008, Jatin Kumar wrote:
> On Wed, Nov 19, 2008 at 3:35 AM, Geert Uytterhoeven <geert@linux-m68k.org>wrote:
> > On Tue, 18 Nov 2008, Jatin Kumar wrote:
> > > I am new to linux fb model and had some queries regarding resolution
> > change
> > > mechanisms.
> > >
> > > Consider a situation where the frambuffer kernel module (vfb/xenfb etc)
> > > wants to change the resolution.
> > >
> > > 1. Is there a mechanism to this, considering the applications/windowing
> > > system/console above the framebuffer hasnt initiated the size change?
> > >
> > > 2. Is there a way to do an upcall into the application/windowing
> > > system/console modules to inform them about the size change
> > asynchronously?
> > >
> > > In this particular case ; the display hardware(instead of the user) has
> > > initiated the resolution change.Is it possible in the current fb
> > framework
> > > to support it?
> >
> > Yes there is! If the resolution is changed, and the number of columns and
> > lines of the console changes, the tty subsystem will send the SIGWINCH
> > signal
> > to the application, cfr. tty_do_resize() in drivers/char/tty_io.c.
> >
> > Note that not all applications handle it. E.g. X doesn't, AFAIK.
> 
> Thanks much for the info.
> 
> Is the tty_io_resize( ) relatively new? .

tty_do_resize

> I am looking at 2.6.18.8 src code (used for xen) and could not find the
> function.

No, it's older than the frame buffer device framework. If you can't find it,
search for SIGWINCH.

> Also are there any plans for exposing a similar callback api in the linux fb
> model to make the applications stay updated about the underlying
> resolution/hardware mode changes?

What exactly are you missing that SIGWINCH doesn't provide?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

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