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From: halli manjunatha <hallimanju@gmail.com>
Date: Wed, 11 Jul 2012 13:37:27 -0500
Message-ID: <CAMT6Pycuhe7OnP7D_FJy1yp2oFH780diTiHxEyTiPpyaaVX9Ug@mail.gmail.com>
Subject: Re: [PATCH 1/5] v4l2: Add rangelow and rangehigh fields to the
 v4l2_hw_freq_seek struct
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Hans de Goede <hdegoede@redhat.com>,
	Linux Media Mailing List <linux-media@vger.kernel.org>
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On Wed, Jul 11, 2012 at 1:01 PM, Hans Verkuil <hverkuil@xs4all.nl> wrote:
> Hi Hans,
>
> Thanks for the patch.
>
> I've CC-ed Halli as well.
>
> On Wed July 11 2012 17:47:34 Hans de Goede wrote:
>> To allow apps to limit a hw-freq-seek to a specific band, for further
>> info see the documentation this patch adds for these new fields.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>  .../DocBook/media/v4l/vidioc-s-hw-freq-seek.xml    |   44 ++++++++++++++++----
>>  include/linux/videodev2.h                          |    5 ++-
>>  2 files changed, 40 insertions(+), 9 deletions(-)
>>
>> diff --git a/Documentation/DocBook/media/v4l/vidioc-s-hw-freq-seek.xml b/Documentation/DocBook/media/v4l/vidioc-s-hw-freq-seek.xml
>> index f4db44d..50dc9f8 100644
>> --- a/Documentation/DocBook/media/v4l/vidioc-s-hw-freq-seek.xml
>> +++ b/Documentation/DocBook/media/v4l/vidioc-s-hw-freq-seek.xml
>> @@ -52,11 +52,21 @@
>>      <para>Start a hardware frequency seek from the current frequency.
>>  To do this applications initialize the <structfield>tuner</structfield>,
>>  <structfield>type</structfield>, <structfield>seek_upward</structfield>,
>> -<structfield>spacing</structfield> and
>> -<structfield>wrap_around</structfield> fields, and zero out the
>> -<structfield>reserved</structfield> array of a &v4l2-hw-freq-seek; and
>> -call the <constant>VIDIOC_S_HW_FREQ_SEEK</constant> ioctl with a pointer
>> -to this structure.</para>
>> +<structfield>wrap_around</structfield>, <structfield>spacing</structfield>,
>> +<structfield>rangelow</structfield> and <structfield>rangehigh</structfield>
>> +fields, and zero out the <structfield>reserved</structfield> array of a
>> +&v4l2-hw-freq-seek; and call the <constant>VIDIOC_S_HW_FREQ_SEEK</constant>
>> +ioctl with a pointer to this structure.</para>
>> +
>> +    <para>The <structfield>rangelow</structfield> and
>> +<structfield>rangehigh</structfield> fields can be set to a non-zero value to
>> +tell the driver to search a specific band. If the &v4l2-tuner;
>> +<structfield>capability</structfield> field has the
>> +<constant>V4L2_TUNER_CAP_HWSEEK_PROG_LIM</constant> flag set, these values
>> +must fall within one of the bands returned by &VIDIOC-ENUM-FREQ-BANDS;. If
>> +the <constant>V4L2_TUNER_CAP_HWSEEK_PROG_LIM</constant> flag is not set,
>> +then these values must exactly match those of one of the bands returned by
>> +&VIDIOC-ENUM-FREQ-BANDS;.</para>
>
> OK, I have some questions here:
>
> 1) If you have a multiband tuner, what should happen if both low and high are
> zero? Currently it is undefined, other than that the seek should start from
> the current frequency until it reaches some limit.
>
> Halli, what does your hardware do? In particular, is the hwseek limited by the
> US/Europe or Japan band range or can it do the full range? If I'm not mistaken
> it is the former, right?

You are right... my hardware seek is limited by the japan/US band range....

> If it is the former, then you need to explicitly set low + high to ensure that
> the hwseek uses the correct range because the driver can't guess which of the
> overlapping bands to use.

Yes in my driver I will take care of this :)....
>
> 2) What happens if the current frequency is outside the low/high range? The
> hwseek spec says that the seek starts from the current frequency, so that might
> mean that hwseek returns -ERANGE in this case.
>
> Regards,
>
>         Hans



-- 
Regards
Halli