FE_READ_STATUS blocking time

[ozgur cagdas]

Hi,

I've recently started experimenting with a DVB-T usb stick and the
intent of this post is to understand if what I am seeing is expected
behaviour or not. Therefore, I am not providing any hw, kernel version
etc details at this point but quite happy to do so if required.

Right, I use the FE_SET_PROPERTY ioctl to tune the front end and then
after 200ms. I call the FE_READ_STATUS ioctl to check the lock status.
My original plan was to call this ioclt periodically until lock is
acquired however, even though the device is opened with the O_NONBLOCK
flag, this call blocks for around 500ms and instead of seeing FEC,
viterbi etc blocks locking in incremental steps, it returns when all
the blocks are locked. Once locked, the subsequent FE_READ_STATUS
calls do return within 30ms.

If I unplug the feed before tune, then, each FE_READ_STATUS blocks for
about 500ms.

I also tried using the 'poll' system call on the FE's fd with POLLIN
but when it returns POLLIN in revents, then again FE_READ_STATUS
blocks around 500ms on the first attempt.

So, is there a way to avoid the FE_READ_STATUS block or is it down to
the individual driver implementation?

Also, is there a better way of monitoring the 'lock' status?

Kind regards,

Oz
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Re: [linux-dvb] soft demux device

[ozgur cagdas]

Lovely! It worked straight away, at least happily created the nodes :) I'm 
hoping to give an update after I manage to find sometime to play with it.

On the other hand, as a small note, I've applied your patch ( 
http://permalink.gmane.org/gmane.linux.drivers.video-input-infrastructure/16540 
) on top of the latest hg clone but linux/drivers/media/dvb/Makefile patch 
failed. It's a very simple patch to apply manually though.

Cheers,

Ozgur.



- Original Message 
From: Andy Walls 
To: linux-media@vger.kernel.org
Cc: linux-...@linuxtv.org
Sent: Wed, February 24, 2010 1:22:32 PM
Subject: Re: [linux-dvb] soft demux device

On Wed, 2010-02-24 at 03:57 -0800, ozgur cagdas wrote:
> Hi,
> 
> Thanks very much for the previous information. To give it a go just as
> it is, I've loaded dvb_dummy_fe module manually and many other modules
> including dvb_core as well, but no hope, don't have /dev/dvb folder
> yet. As I've mentioned earlier, I do not have a hardware at the
> moment, so I should trigger loading of proper modules manually. In my
> scenario, which modules should I load? Any simple set of modules
> that'd create necessary /dev/dvb/ and subsequent would do for me. If
> it matters, I am using 2.6.31 kernel and ubuntu 9.10 distribution.

See my dvb_dummy_adapter patch I just posted to the list.

Regards,
Andy

> Cheers,
> 
> Ozgur.
> 
> 
>  
> 
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> linux-...@linuxtv.org
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> 


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