Date: Fri, 2 Mar 2001 10:02:47 -0800 (PST) From: Richard Hodges <rh@matriplex.com> To: Dmitry Dicky <diwil@eis.ru> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: stupid device driver question Message-ID: <Pine.BSF.4.10.10103020956490.48242-100000@mail.matriplex.com> In-Reply-To: <XFMail.010302180256.diwil@eis.ru>
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On Fri, 2 Mar 2001, Dmitry Dicky wrote:
> Hi fellows,
>
> I'm writing some device driver which should pass some data to the user
> space.
>
> The part of the device read routine looks as follows:
>
> ----------------------------------
> int
> dev_read(dev_t dev, struct uio *uio, int ioflag)
> {
> int err = 0;
> /* ... */
> amnt = MIN(uio->uio_resid, cntw);
> /* Wait here until data available .... how? */
> err = uiomove(buf2, amnt, uio);
> if (err != 0) {
> return(err);
> }
>
> memset(buf2, 0, amnt);
> cntw -= amnt;
> return 0;
> }
> -------------------------------------
> User application hands on read(2).
>
> But buf2 being filled upon some event and 'dev_read' should
> wait until data in buf2 available.
>
> So, the question is:
> How can I hang dev_read, issue some signal and then continue uiomove(9)
> data to the user space?
How about something like:
int timeout;
timeout = hz; /* fail if nothing in one second */
while(timeout && (NOTREADY))
if(tsleep(softc, PRIBIO, "mydev", 1))
timeout--;
if(NOTREADY)
return(EIO); /* or whatever... */
uiomove(...)
Then in your interrupt service routine:
wakeup(softc);
Hope this helps!
-Richard
-------------------------------------------
Richard Hodges | Matriplex, inc.
Product Manager | 769 Basque Way
rh@matriplex.com | Carson City, NV 89706
775-886-6477 | www.matriplex.com
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