From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.kapsi.fi ([217.30.184.167]:44223 "EHLO mail.kapsi.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751332Ab3LQVJM (ORCPT ); Tue, 17 Dec 2013 16:09:12 -0500 Message-ID: <52B0BD72.9000804@iki.fi> Date: Tue, 17 Dec 2013 23:09:06 +0200 From: Antti Palosaari MIME-Version: 1.0 To: Devin Heitmueller , Connor Behan CC: Mauro Carvalho Chehab , Frederik Himpe , Linux Kernel , Linux Media Mailing List Subject: Re: stable regression: tda18271_read_regs: [1-0060|M] ERROR: i2c_transfer returned: -19 References: <1386969579.3914.13.camel@piranha.localdomain> <20131214092443.622b069d@samsung.com> <52ACE809.1000406@gmail.com> <52AFE107.4040705@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: Off-topic, Cc:s dropped, related to DVB / V4L2 tuner communication problems. On 17.12.2013 07:39, Devin Heitmueller wrote: > Hi Connor, > > On Tue, Dec 17, 2013 at 12:28 AM, Connor Behan wrote: >> Thanks for the detailed answer. I have tried your patch and updated the >> wiki page. Would a 950 or 950Q be safer to buy next time? > > The 950 has long since been obsoleted. You cannot buy them anymore. > The 950q though is well supported and doesn't have this issue as it > uses a different chip. > >> On 14/12/13 05:17 PM, Devin Heitmueller wrote: >>> I had a patch kicking around which fixed part of the issue, but it >>> didn't completely work because of the lgdt3305 having AGC enabled at >>> chip powerup (which interferes with analog tuning on the shared >>> tuner), and the internal v4l-dvb APIs don't provide any easy way to >>> reset the AGC from the analog side of the device. >> >> By this do you mean that the functions exist but they aren't part of the >> public API? Maybe this problem can be addressed if there is ever "v4l3" >> or some other reason to break compatibility. > > No, these are internal APIs that dictate how the various driver > components talk to each other. Because the V4L and DVB subsystems > were developed independently of each other, they do a really crappy > job of communicating between them (a problem which manifests itself in > particular when sharing hardware resources such as tuners). > > The problem *can* be fixed, but it would likely require > extensions/changes to the basic frameworks used to communicate between > the different drivers. That shared DVB / V4L2 tuner is one problem that I have also currently (SDR is on V4L2 API and DTV is provided via DVB API). I have decided to try model where I separate RF tuner totally independent used DVB / V4L2 APIs, just to plain I2C driver model. Idea is here to provide needed set of general callbacks and communication and device binding is done via I2C driver model. I am not sure though if there is any big caveats I haven't realized yet... regards Antti -- http://palosaari.fi/