[ECOS] Re: Waiting I/O operation

Sergei Gavrikov w3sg@SoftHome.net
Sat Jul 21 15:11:00 GMT 2007


On Sat, Jul 21, 2007 at 03:19:55PM +0200, Uwe Kindler wrote:
> This is what the documentation says about flags and DSRs:
> 
> http://ecos.sourceware.org/docs-latest/ref/kernel-flags.html
> 
> So it seems to be possible to use cyg_flag_setbits() from DSRs.

> Andrew Lunn schrieb:
> >>But, one my today DSR uses the cyg_flag_setbits() notifier and that
> >>works as I could expect. I found that is more simple, because that
> >>doesn't need itself in a mutex. I wonder about the right hacking from
> >>the eCos experts.
> >
> >You are not allowed to block in a DSR. So look through the
> >cyg_flag_setbits() code and see if it calls any functions to block
> >itself. 
> >
> >        Andrew

Hello,

As I could understand Andrew's main concern, that is, We aren't allowed
to block in a DSR (cyg_flag_setbits() do it), and I am agree with him. I
looked at the common hal's drv_api.c against the kernel's flag.cxx.  As
I could see the cyg_drv_cond_*() calls are almost the atomic funcs. I
wouldn't say same thing about the kernel's Cyg_Flag::setbits().

More that, I liked cyg_drv_cond_wait(), because that is just it

while (cond->wait == 1) { call_dsrs (); }

So, my application can be a kernel-less application too. I think the
table from Chapter 13 is a good guide-line: a what allowed us to run
from DSR:

http://ecos.sourceware.org/docs-latest/ref/devapi-synchronization-levels.html

So, I did believe in that two crosses more after Andrew's suggest to
U.T.S.L :-) I did believe in those crosses even more after a comparation

  find $ECOS_REPOSITORY/{io,devs} | xargs grep cyg_drv_cond_

    against

  find $ECOS_REPOSITORY/{io,devs} | xargs grep cyg_flag_

We all did talk about the DSR's possibilities, didn't all? IMHO, that is
in the most an eCos driver related thing.

        Sergei


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