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Date: Tue, 19 Jun 2012 18:47:37 +0200
From: Hans de Goede <hdegoede@redhat.com>
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To: Mauro Carvalho Chehab <mchehab@redhat.com>
CC: Hans Verkuil <hverkuil@xs4all.nl>, linux-media@vger.kernel.org,
	halli manjunatha <hallimanju@gmail.com>,
	Hans Verkuil <hans.verkuil@cisco.com>
Subject: Re: [RFCv2 PATCH 4/6] videodev2.h: add frequency band information.
References: <1338202005-10208-1-git-send-email-hverkuil@xs4all.nl> <005651489cd5c9f832df2d5d90e19e2eee07c9b9.1338201853.git.hans.verkuil@cisco.com> <4FDFCC0F.9000208@redhat.com> <4FE037FE.7030804@redhat.com> <4FE05DF4.7030905@redhat.com> <4FE07255.6050606@redhat.com> <4FE08942.8020603@redhat.com>
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Hi,

<snip long discussion about having a fixed set of bands versus
  a way to enumerate bands, including their rangelow, rangehigh
  and capabilities>

Ok, you've convinced me. I agree that having a way to actually
enumerate ranges, rather then having a fixed set of ranges, is
better.

Which brings us back many weeks to the proposal for making
it possible to enumerate bands on radio devices. Rather
then digging up the old mails lets start anew, I propose
the following API for this:

1. A radio device can have multiple tuners, but only 1 can
be active (streaming audio to the associated audio input)
at the same time.

2. Radio device tuners are enumerated by calling G_TUNER
with an increasing index until EINVAL gets returned

3. G_FREQUENCY will always return the frequency and index
of the currently active tuner

4. When calling S_TUNER on a radio device, the active
tuner will be set to the v4l2_tuner index field

5. When calling S_FREQUENCY on a radio device, the active
tuner will be set to the v4l2_frequency tuner field

6. On a G_TUNER call on a radio device the rxsubchans,
audmode, signal and afc v4l2_tuner fields are only
filled on for the active tuner (as returned by
G_FREQUENCY) for inactive tuners these fields are reported
as 0.


This is pretty close to what the cadet driver currently does,
the differences are point 5 and 6, currently wrt point 5 the
cadet driver just ignores the tuner field, and wrt point 6
it always tries to fill in these fields, reporting ie the
FM signal strength when the FM tuner is active as signal
for the AM tuner too.

Regards,

Hans