[linux-dvb] PROC_FS patch and other stuff

[Dennis <dennis.noordsij@wiral.com>]

Hi,

I have made a patch to add procfs support to the DVB HEAD drivers, which gives 
you something like:

/proc/dvb/
/proc/dvb/adapter1
/proc/dvb/adapter1/frontend0
/proc/dvb/adapter1/frontend0/inversion
/proc/dvb/adapter1/frontend0/symbol_rate
/proc/dvb/adapter1/frontend0/modulation
/proc/dvb/adapter1/frontend0/pwm
/proc/dvb/adapter1/frontend0/ves1820
/proc/dvb/adapter1/frontend0/ber
/proc/dvb/adapter1/frontend0/uncorrected_blocks
/proc/dvb/adapter1/frontend0/signal_strength
/proc/dvb/adapter1/frontend0/SNR
/proc/dvb/adapter1/frontend0/status
/proc/dvb/adapter1/frontend0/caps
/proc/dvb/adapter1/frontend0/type
/proc/dvb/adapter1/frontend0/identify
/proc/dvb/adapter1/frontend0/frequency
/proc/dvb/adapter1/identify
/proc/dvb/adapter0
/proc/dvb/adapter0/frontend0
/proc/dvb/adapter0/frontend0/inversion
/proc/dvb/adapter0/frontend0/symbol_rate
/proc/dvb/adapter0/frontend0/modulation
/proc/dvb/adapter0/frontend0/pwm
/proc/dvb/adapter0/frontend0/ves1820
/proc/dvb/adapter0/frontend0/ber
/proc/dvb/adapter0/frontend0/uncorrected_blocks
/proc/dvb/adapter0/frontend0/signal_strength
/proc/dvb/adapter0/frontend0/SNR
/proc/dvb/adapter0/frontend0/status
/proc/dvb/adapter0/frontend0/caps
/proc/dvb/adapter0/frontend0/type
/proc/dvb/adapter0/frontend0/identify
/proc/dvb/adapter0/frontend0/frequency
/proc/dvb/adapter0/identify


Most items will look familiar, all of them output the current value, and the 
relevant ones allow you to echo in a new value.

So you can tune a card by:
echo "162000000" > /proc/dvb/adapter0/frontend0/frequency
echo "QAM_64" > /proc/dvb/adapter0/frontend0/modulation
echo "6900000" > /proc/dvb/adapter0/frontend0/symbol_rate

(NOTE: only DVB-C supported right now! But the DVB-C related proc entries are 
only created if you have a DVB-C card, so if you try this with DVB-S or -T 
you'll just get fewer proc entries).

and do:
cat /proc/dvb/adapter0/frontend0/status
FE_HAS_SIGNAL
FE_HAS_CARRIER
FE_HAS_VITERBI
FE_HAS_SYNC
FE_HAS_LOCK

Now, while a lot of fun can be had with this, my initial reason to write this 
was to allow easy changing of the ves1820 register values, and the cards PWM 
value, without recompiling the driver. This in order to find more optimal 
values, and to be able to do it with a bash script :-)

Hence:
vdr driver # cat /proc/dvb/adapter0/frontend0/ves1820
VES1820 Register settings
(QAM type, Register 1, Register 5, Register 8, Register 9)
  QAM_16    140   164   162   145
  QAM_32    140   120   116   150
  QAM_64    106    70    67   106
  QAM_128   106    54    52   126
  QAM_256    92    38    35   107

And you can change these by for example:
echo "QAM_16 111 222 333 444" > ./ves1820

Also the /proc/dvb/adapterX/frontend0/pwm value can be changed like this.

After a lot of playing with the register values, I got slight improvements in 
BER value, but not much, and still a lot of block errors. For QAM_64, BER is 
like 10,000, but for QAM_128, it is usually 600,000.

The PWM value however, I changed from 52 (other card default is 21?), to 40, 
("echo 40 > /proc/dvb/adapter0/frontend0/pwm") and now have a QAM_128 BER of 
10,000, and no block errors! Massive improvement, since before I used to 
always have problems watching QAM_128 channels. The 40 value was a random 
number I pulled out of an unnamed place :)

Anyways, this patch is probably nowhere near clean enough to add to the 
drivers, but I think a lot of good things can be done with proc filesystem 
support, and will happily take pointers from more knowledgable people on this 
list in order to improve and add on this. 
For example to add support of per-card register and PWM values I had to 
shuffle a few things around. Some proc related functions should also be in 
their own file.

So this is basically for the people who are interested in playing with the 
ves1820 register and PWM values to find the optimal values. You can now do so 
without recompiling, and the first one to write a nice Perl script (BASH is 
OK too :-) to scan for the best values gets a free beer!

Cheers,
Dennis

PS - There are a few additional printk's etc I have added over time to play 
with, which are not really part of anything, and which I'll take out for the 
"proper" patch.

PS2 - If you have PROC_FS enabled in your kernel, this patch will build with 
PROC_FS automatically. If you disable this in dvb_procfs.h, you should get 
the normal, clean HEAD driver.



-- This is where I put the patch last night, not as an attachment, but it 
never went through anyway, probably too big? (35kb). Any suggestions where to 
make it available? :-)



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