This is the logic that:
  a) Ensures /sys/class/pvrusb2/sn-*/ctl_frequency/{max,min}_val are
     "automagically" reset to sane values on each mode change.

  b) Allows tuning to a radio frequency by something like:
     echo `perl -e "print int(94.9*16000 + 0.5)"` \
       > /sys/class/pvrusb2/sn-*/ctl_input/cur_val


The trick was to take advantage of the already existing .get_{min,max}_value
function pointers in pvr2_ctrl, to "dynamically override" the hardcoded values
for min/max frequency at runtime.

For a moment I thought to dispose of the hardcoded MIN/MAX_FREQ and use the
hirange/lowrange fields of the v4l2_tuner struct instead, but then I see that
tuner-core.c kinda hardcodes these as well, so I decided to not bother.
Signed-off-by: NPantelis Koukousoulas <pakt223@freemail.gr>
Signed-off-by: NMike Isely <isely@pobox.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>

This is the logic that supports switching modes via e.g.,
  echo radio > /sys/class/pvrusb2/sn-*/ctl_input/cur_val.

To do the mode switching we need to:
a) broadcast AUDC_SET_RADIO and
b) issue the CX2341X_ENC_MUTE_VIDEO command to the encoder. 

The first is done by adding a new pvr2_i2c_op and having it trigger on 
input change, the second by adding this command in pvr2_encoder_start() 
and requesting an encoder restart on input change by setting 
stale_subsys_mask appropriately. 

The clues about AUDC_SET_RADIO and CX2341X_ENC_MUTE_VIDEO were kindly 
provided by Hans Verkuil on the pvrusb2 mailing list. The idea to 
implement mode switching this way (on input change) is due to Mike Isely.

Why AUDC_SET_RADIO/VIDIOC_S_STD are used for switching? I can 't be sure, 
but I think this can be traced to a cornell student being the first to 
implement radio support in ivtv "as a different standard". I think the 
rest just evolved from there (it 's in the ivtv ML archives).
Signed-off-by: NPantelis Koukousoulas <pakt223@freemail.gr>
Signed-off-by: NMike Isely <isely@pobox.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/pvrusb2/pvrusb2-i2c-cmd-v4l2.c: In function 'set_standard':
drivers/media/video/pvrusb2/pvrusb2-i2c-cmd-v4l2.c:33: warning: format '%llx' expects type 'long long unsigned int', but argument 2 has type 'v4l2_std_id'
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>

Signed-off-by: NMike Isely <isely@pobox.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>

Implement V4L2 driver for the Hauppauge PVR USB2 TV tuner.

The Hauppauge PVR USB2 is a USB connected TV tuner with an embedded
cx23416 hardware MPEG2 encoder.  There are two major variants of this
device; this driver handles both.  Any V4L2 application which
understands MPEG2 video stream data should be able to work with this
device.
Signed-off-by: NMike Isely <isely@pobox.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>