linux-fbdev-devel

[Linux-fbdev-devel] open and close semanthics

[Alessio S. <al...@ma...>]

Hi, can somebody give me an authoritative answer:
what is the semanthics associated to the "open" and "release" (close) calls?

More specifically, "open" and "release" can/must/must not change any 
setting (resolution etc)?

Should those functions keep a "counter" of how many programs opened it?

bye, thank you
Alessio

Re: [Linux-fbdev-devel] open and close semanthics

[Alessio S. <al...@ma...>]

No indications on this request?
thank you
Alessio




Alessio Sangalli wrote:
> Hi, can somebody give me an authoritative answer:
> what is the semanthics associated to the "open" and "release" (close) calls?
> 
> More specifically, "open" and "release" can/must/must not change any 
> setting (resolution etc)?
> 
> Should those functions keep a "counter" of how many programs opened it?

Re: [Linux-fbdev-devel] open and close semanthics

[Florian T. S. <Flo...@gm...>]

Hi,

this is not authoritative but I hope that's better than no answer:

Alessio Sangalli schrieb:
> Hi, can somebody give me an authoritative answer:
> what is the semanthics associated to the "open" and "release" (close) calls?
> 
> More specifically, "open" and "release" can/must/must not change any 
> setting (resolution etc)?
> 
> Should those functions keep a "counter" of how many programs opened it?

I'd say that's not well defined. skeletonfb lists them even as optional. 
I've read that some drivers use it for mode changes, some keep counters 
and others just return 0.
If you are writing a driver: use it as you need it or don't use it at all.
If you write something that needs this behavior: there is none you can 
expect along all drivers, sorry.

For more information:
http://www.linux-fbdev.org/HOWTO/4.html
<linux kernel tree>/drivers/video/skeletonfb.c


Regards,

Florian Tobias Schandinat

Re: [Linux-fbdev-devel] open and close semanthics

[Ondrej Z. <san...@cr...>]

On Tue, Aug 25, 2009 at 03:48:57PM -0700, Alessio Sangalli wrote:
> Hi, can somebody give me an authoritative answer:
> what is the semanthics associated to the "open" and "release" (close) calls?
> 
> More specifically, "open" and "release" can/must/must not change any 
> setting (resolution etc)?

Many drivers for non-embedded (VGA compatible) cards assume that they
should not touch hardware if their device is not open. So they configure
device during the first open and restore original state during the
last close. The framebuffer console counts as one user, and therefore
keeps the device configured.

-- 
Elen sila lumenn' omentielvo

Ondrej 'SanTiago' Zajicek (email: san...@cr...)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."

Re: [Linux-fbdev-devel] open and close semanthics

[Alessio S. <al...@ma...>]

> On Tue, Aug 25, 2009 at 03:48:57PM -0700, Alessio Sangalli wrote:
>> Hi, can somebody give me an authoritative answer:

Thank you for all answers.

bye
as