Hi Hans,
On 07/11/2012 08:01 PM, Hans Verkuil 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 <hdego...@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.
That would be driver specific, we could add the same "If rangelow/high is zero
a reasonable default value is used." language as used for the spacing. For
example for the si470x if both are zero I simply switch to the "Japan wide"
band which covers all frequencies handled by the other bands, but if there
is no such covers all ranges band, then the logical thing todo would just keep
the band as is (so as determined by the last s_freq).
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?
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.
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.
What the si470x code currently does is just clamp the frequency to the new
range before seeking, but -ERANGE works for me too.
Regards,
Hans
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