linux-kernel - Re: [PATCH 15/31] media: dvb-frontend invoke enable/disable

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <56AA48FA.7070203@osg.samsung.com>
Date:	Thu, 28 Jan 2016 09:59:38 -0700
From:	Shuah Khan <shuahkh@....samsung.com>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>
Cc:	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, Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [PATCH 15/31] media: dvb-frontend invoke enable/disable_source
 handlers

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) {

>>
>> Also, 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


-- 
Shuah Khan
Sr. Linux Kernel Developer
Open Source Innovation Group
Samsung Research America (Silicon Valley)
shuahkh@....samsung.com | (970) 217-8978