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Message-ID: <20160128153147.199ec4f6@recife.lan>
Date:	Thu, 28 Jan 2016 15:31:47 -0200
From:	Mauro Carvalho Chehab <mchehab@....samsung.com>
To:	Shuah Khan <shuahkh@....samsung.com>
Cc:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>, tiwai@...e.com,
	clemens@...isch.de, hans.verkuil@...co.com,
	laurent.pinchart@...asonboard.com, sakari.ailus@...ux.intel.com,
	javier@....samsung.com, pawel@...iak.com, m.szyprowski@...sung.com,
	kyungmin.park@...sung.com, perex@...ex.cz, arnd@...db.de,
	dan.carpenter@...cle.com, tvboxspy@...il.com, crope@....fi,
	ruchandani.tina@...il.com, corbet@....net, chehabrafael@...il.com,
	k.kozlowski@...sung.com, stefanr@...6.in-berlin.de,
	inki.dae@...sung.com, jh1009.sung@...sung.com,
	elfring@...rs.sourceforge.net, prabhakar.csengg@...il.com,
	sw0312.kim@...sung.com, p.zabel@...gutronix.de,
	ricardo.ribalda@...il.com, labbott@...oraproject.org,
	pierre-louis.bossart@...ux.intel.com, ricard.wanderlof@...s.com,
	julian@...st.de, takamichiho@...il.com, dominic.sacre@....de,
	misterpib@...il.com, daniel@...que.org, gtmkramer@...all.nl,
	normalperson@...t.net, joe@...po.co.uk, linuxbugs@...tgam.net,
	johan@...ud.se, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org, linux-api@...r.kernel.org,
	alsa-devel@...a-project.org
Subject: Re: [PATCH 15/31] media: dvb-frontend invoke enable/disable_source
 handlers

Em Thu, 28 Jan 2016 09:59:38 -0700
Shuah Khan <shuahkh@....samsung.com> escreveu:

> On 01/28/2016 09:07 AM, One Thousand Gnomes wrote:
> > On Thu, 28 Jan 2016 13:53:04 -0200
> > Mauro Carvalho Chehab <mchehab@....samsung.com> wrote:
> >   
> >> Em Wed,  6 Jan 2016 13:27:04 -0700
> >> Shuah Khan <shuahkh@....samsung.com> escreveu:
> >>  
> >>> Checking for tuner availability from frontend thread start
> >>> disrupts video stream. Change to check for tuner and start
> >>> pipeline from frontend open instead and stop pipeline from
> >>> frontend release.    
> >>
> >> That's wrong, as DVB can be opened on read-only mode, where
> >> it won't be changing anything.  
> 
> Correct. Please check the code. Tuner availability check is
> done when the device is opened in Write mode in the following
> conditional.
> 
>        if ((file->f_flags & O_ACCMODE) != O_RDONLY) {

OK.

Thanks!
Mauro
, I don't think POSIX allows to return an error like EBUSY
> >> on open:
> >> 	http://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html  
> > 
> > It doesn't document all the errors you may return. Quite a lot of
> > kernel drivers return EBUSY when they are "single open" things.
> > 
> > POSIX documents certain cases that *must* error and what the error code
> > is. It documents certain possible failures and what their error code is.
> > Beyond that it's up to you.
> >   
> 
> Returning EBUSY clearly indicates the reason why the device
> can't be opened in this case.
> 
> thanks,
> -- Shuah
> 
> 
Thanks!
Mauro

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