From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.kapsi.fi ([217.30.184.167]:51343 "EHLO mail.kapsi.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751945AbaCLNHH (ORCPT ); Wed, 12 Mar 2014 09:07:07 -0400 Message-ID: <53205BF6.9040304@iki.fi> Date: Wed, 12 Mar 2014 15:07:02 +0200 From: Antti Palosaari MIME-Version: 1.0 To: Mauro Carvalho Chehab CC: LMML Subject: Re: [REVIEW PATCH 11/13] DocBook: document RF tuner bandwidth controls References: <1393460528-11684-1-git-send-email-crope@iki.fi> <1393460528-11684-12-git-send-email-crope@iki.fi> <20140305154922.508c48d7@samsung.com> <531D8D78.800@iki.fi> <20140312080233.3823dd80@samsung.com> <5320527B.9040707@iki.fi> <20140312094739.089a8ce5@samsung.com> <532059B0.9010201@iki.fi> In-Reply-To: <532059B0.9010201@iki.fi> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 12.03.2014 14:57, Antti Palosaari wrote: > On 12.03.2014 14:47, Mauro Carvalho Chehab wrote: >> Em Wed, 12 Mar 2014 14:26:35 +0200 >> Antti Palosaari escreveu: >> >>> On 12.03.2014 13:02, Mauro Carvalho Chehab wrote: >>>> Em Mon, 10 Mar 2014 12:01:28 +0200 >>>> Antti Palosaari escreveu: >>>> >>>>> On 05.03.2014 20:49, Mauro Carvalho Chehab wrote: >>>>>> Em Thu, 27 Feb 2014 02:22:06 +0200 >>>>>> Antti Palosaari escreveu: >>>>>> >>>>>>> Add documentation for RF tuner bandwidth controls. These controls >>>>>>> are >>>>>>> used to set filters on tuner signal path. >>>>>>> >>>>>>> Cc: Hans Verkuil >>>>>>> Signed-off-by: Antti Palosaari >>>>>>> --- >>>>>>> Documentation/DocBook/media/v4l/controls.xml | 19 >>>>>>> +++++++++++++++++++ >>>>>>> 1 file changed, 19 insertions(+) >>>>>>> >>>>>>> diff --git a/Documentation/DocBook/media/v4l/controls.xml >>>>>>> b/Documentation/DocBook/media/v4l/controls.xml >>>>>>> index 6c9dbf6..5550fea 100644 >>>>>>> --- a/Documentation/DocBook/media/v4l/controls.xml >>>>>>> +++ b/Documentation/DocBook/media/v4l/controls.xml >>>>>>> @@ -5007,6 +5007,25 @@ descriptor. Calling &VIDIOC-QUERYCTRL; for >>>>>>> this control will return a >>>>>>> description of this control class. >>>>>>> >>>>>>> >>>>>>> + >>>>>> spanname="id">V4L2_CID_RF_TUNER_BANDWIDTH_AUTO  >>>>>>> >>>>>>> + boolean >>>>>>> + >>>>>>> + >>>>>>> + Enables/disables tuner >>>>>>> radio channel >>>>>>> +bandwidth configuration. In automatic mode bandwidth >>>>>>> configuration is performed >>>>>>> +by the driver. >>>>>>> + >>>>>>> + >>>>>>> + >>>>>> spanname="id">V4L2_CID_RF_TUNER_BANDWIDTH  >>>>>>> >>>>>>> + integer >>>>>>> + >>>>>>> + >>>>>>> + Filter(s) on tuner signal >>>>>>> path are used to >>>>>>> +filter signal according to receiving party needs. Driver >>>>>>> configures filters to >>>>>>> +fulfill desired bandwidth requirement. Used when >>>>>>> V4L2_CID_RF_TUNER_BANDWIDTH_AUTO is not >>>>>>> +set. The range and step are driver-specific. >>>>>> >>>>>> Huh? If this is enable/disable, why "the range and step are >>>>>> driver-specific"? >>>>> >>>>> Because there is two controls grouped. That is situation of having >>>>> AUTO/MANUAL. >>>>> V4L2_CID_RF_TUNER_BANDWIDTH_AUTO >>>>> V4L2_CID_RF_TUNER_BANDWIDTH >>>>> >>>>> V4L2_CID_RF_TUNER_BANDWIDTH is valid only when >>>>> V4L2_CID_RF_TUNER_BANDWIDTH_AUTO == false. >>>>> >>>> >>>> Sorry, but I'm not understanding what you're arguing. >>>> >>>> Yeah, it is clear at the patch that there are two controls, and that >>>> V4L2_CID_RF_TUNER_BANDWIDTH is valid only when AUTO is disabled, but >>>> this doesn't answer my question: >>>> >>>> Why V4L2_CID_RF_TUNER_BANDWIDTH's range and step are driver-specific? >>>> >>> >>> Hmmm. That control is used to configure RF filters. Filters set >>> bandwidth of radio channel. There is usually quite limited set of >>> available analog filters inside RF tuner. If you look for example >>> FC0012/FC0013 possible filters are 6/7/8 MHz. E4000 has something 4-11 >>> MHz. If you look those very old 1st gen silicon tuners like QT1010 / >>> MT2060, there is no integrated filters at all - but there is external >>> saw filter which is usually 8MHz at 36.125 MHz IF. >>> >>> Did you remember there is same parameter already in DVB API (struct >>> dtv_frontend_properties bandwidth_hz)? That is control is currently used >>> to set r820t, fc0012, fc10013 .bandwidth_hz value, e4000 implements it >>> correctly as own control. >>> >>> I am quite astonished we have that big gap with our views. >> >> Well, on DVB, the bandwidth is specified in Hz, at DVBv5 (or via >> an enum on DVBv3). >> >> Here, there's no description about the unit to be used (Hz? kHz?). >> It just says that this is an integer, with a driver-specific >> range and step. >> >> So, one driver might choose to use Hz, other kHz, and other to >> expose some internal counter. That's bad. >> >> We should either use a V4L2_CTRL_TYPE_MENU type of control, where it >> would be possible to do something similar to DVBv3 way to specify >> the bandwidth filter, or to define that the bandwidth will be >> in Hz, kHz or MHz. > > Yeah, indeed. That was my mistake. The aim was Hz yes. > >> >> Probably, a menu type is better, as it allows userspace to get >> all supported bandwidths. > > I though it too, but there is already a lot choices for some tuners, > E4000 has over 30. What is maximum reasonable filter count for > V4L2_CTRL_TYPE_MENU? One fear there is also what happens when there will be some day new RF tuner having DSP which does digital filtering ~1 Hz step? Mabbe the current control is enough, but probably it is place to add comment unit is Hz (even I think people should expect it is Hz when RF frequencies are spoken). regards Antti -- http://palosaari.fi/