linux-kernel - Re: [RFC] vtunerc: virtual DVB device - is it ok to NACK driver because of worrying about possible misusage?

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Date:	Mon, 5 Dec 2011 00:54:24 +0100
From:	HoP <jpetrous@...il.com>
To:	Devin Heitmueller <dheitmueller@...nellabs.com>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, VDR User <user.vdr@...il.com>,
	Andreas Oberritter <obi@...uxtv.org>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] vtunerc: virtual DVB device - is it ok to NACK driver
 because of worrying about possible misusage?

Devin,

I perfectly remember your opinion regarding vtuner.

2011/12/3 Devin Heitmueller <dheitmueller@...nellabs.com>:
> On Sat, Dec 3, 2011 at 12:42 PM, Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
>> On Sat, 3 Dec 2011 09:21:23 -0800
>> VDR User <user.vdr@...il.com> wrote:
>>
>>> On Sat, Dec 3, 2011 at 8:13 AM, Andreas Oberritter <obi@...uxtv.org> wrote:
>>> > You could certainly build a library to reach a different goal. The goal
>>> > of vtuner is to access remote tuners with any existing program
>>> > implementing the DVB API.
>>>
>>> So you could finally use VDR as a server/client setup using vtuner,
>>> right? With full OSD, timer, etc? Yes, I'm aware that streamdev
>>> exists. It was horrible when I tried it last (a long time ago) and I
>>> understand it's gotten better. But it's not a suitable replacement for
>>> a real server/client setup. It sounds like using vtuner, this would
>>> finally be possible and since Klaus has no intention of ever
>>> modernizing VDR into server/client (that I'm aware of), it's also the
>>> only suitable option as well.
>>
>> I would expect it to still suck. One of the problems you have with trying
>> to pretend things are not networked is that you fake asynchronous events
>> synchronously, you can't properly cover error cases and as a result you
>> get things like ioctls that hang for two minutes or fail in bogus and
>> bizarre ways. If you loop via userspace you've also got to deal with
>> deadlocks and all sorts of horrible cornercases like the user space
>> daemon dying.
>>
>> There is a reason properly working client/server code looks different -
>> it's not a trivial transformation and faking it kernel side won't be any
>> better than faking it in user space - it may well even be a worse fake.
>>
>> Alan
>
> This whole notion of creating fake kernel devices to represent
> networked tuners feels like a hack.  If applications want to access
> networked tuners, adding support for RTP/RTSP or incorporating
> libhdhomerun (LGPL) is a fairly straightforward exercise.  In fact,
> many applications already have incorporated support for one of these
> two approaches.  The fact that app maintainers have been
> unwilling/uninterested to do such doesn't feel like it should be an
> excuse for hacking this functionality into the kernel.

Still the same nonsense - why I should add 10x or even 100 times more
code to achieve not the same but may be 80-90% same result?

The idea is hell simple = allow to use those remote tuners by
100% of dvb api compliant applications. Not 80%, but 100%.

Honza
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