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This README escorted the skystar2-driver rewriting procedure. It describes the
state of the new flexcop-driver set and some internals are written down here
too.

This document hopefully describes things about the flexcop and its
device-offsprings. Goal was to write an easy-to-write and easy-to-read set of
drivers based on the skystar2.c and other information.

Remark: flexcop-pci.c was a copy of skystar2.c, but every line has been
touched and rewritten.

History & News
==============
  2005-04-01 - correct USB ISOC transfers (thanks to Vadim Catana)




General coding processing
=========================

We should proceed as follows (as long as no one complains):

0) Think before start writing code!

1) rewriting the skystar2.c with the help of the flexcop register descriptions
and splitting up the files to a pci-bus-part and a flexcop-part.
The new driver will be called b2c2-flexcop-pci.ko/b2c2-flexcop-usb.ko for the
device-specific part and b2c2-flexcop.ko for the common flexcop-functions.

2) Search for errors in the leftover of flexcop-pci.c (compare with pluto2.c
and other pci drivers)

3) make some beautification (see 'Improvements when rewriting (refactoring) is
done')

4) Testing the new driver and maybe substitute the skystar2.c with it, to reach
a wider tester audience.

5) creating an usb-bus-part using the already written flexcop code for the pci
card.

Idea: create a kernel-object for the flexcop and export all important
functions. This option saves kernel-memory, but maybe a lot of functions have
to be exported to kernel namespace.


Current situation
=================

0) Done :)
1) Done (some minor issues left)
2) Done
3) Not ready yet, more information is necessary
4) next to be done (see the table below)
5) USB driver is working (yes, there are some minor issues)

What seems to be ready?
-----------------------

1) Rewriting
1a) i2c is cut off from the flexcop-pci.c and seems to work
1b) moved tuner and demod stuff from flexcop-pci.c to flexcop-tuner-fe.c
1c) moved lnb and diseqc stuff from flexcop-pci.c to flexcop-tuner-fe.c
1e) eeprom (reading MAC address)
1d) sram (no dynamic sll size detection (commented out) (using default as JJ told me))
1f) misc. register accesses for reading parameters (e.g. resetting, revision)
1g) pid/mac filter (flexcop-hw-filter.c)
1i) dvb-stuff initialization in flexcop.c (done)
1h) dma stuff (now just using the size-irq, instead of all-together, to be done)
1j) remove flexcop initialization from flexcop-pci.c completely (done)
1l) use a well working dma IRQ method (done, see 'Known bugs and problems and TODO')
1k) cleanup flexcop-files (remove unused EXPORT_SYMBOLs, make static from
non-static where possible, moved code to proper places)

2) Search for errors in the leftover of flexcop-pci.c (partially done)
5a) add MAC address reading
5c) feeding of ISOC data to the software demux (format of the isochronous data
and speed optimization, no real error) (thanks to Vadim Catana)

What to do in the near future?
--------------------------------------
(no special order here)

5) USB driver
5b) optimize isoc-transfer (submitting/killing isoc URBs when transfer is starting)

Testing changes
---------------

O             = item is working
P             = item is partially working
X             = item is not working
N             = item does not apply here
<empty field> = item need to be examined

       | PCI                               | USB
item   | mt352 | nxt2002 | stv0299 | mt312 | mt352 | nxt2002 | stv0299 | mt312
-------+-------+---------+---------+-------+-------+---------+---------+-------
1a)    | O     |         |         |       | N     | N       | N       | N
1b)    | O     |         |         |       |       |         | O       |
1c)    | N     | N       |         |       | N     | N       | O       |
1d)    |                 O                 |                 O
1e)    |                 O                 |                 O
1f)    |                                   P
1g)    |                                   O
1h)    |                 P                 |
1i)    |                 O                 |                 N
1j)    |                 O                 |                 N
1l)    |                 O                 |                 N
2)     |                 O                 |                 N
5a)    |                 N                 |                 O
5b)*   |                 N                 |
5c)    |                 N                 |                 O

* - not done yet

Known bugs and problems and TODO
--------------------------------

1g/h/l) when pid filtering is enabled on the pci card

DMA usage currently:
  The DMA is splitted in 2 equal-sized subbuffers. The Flexcop writes to first
  address and triggers an IRQ when it's full and starts writing to the second
  address. When the second address is full, the IRQ is triggered again, and
  the flexcop writes to first address again, and so on.
  The buffersize of each address is currently 640*188 bytes.

  Problem is, when using hw-pid-filtering and doing some low-bandwidth
  operation (like scanning) the buffers won't be filled enough to trigger
  the IRQ. That's why:

  When PID filtering is activated, the timer IRQ is used. Every 1.97 ms the IRQ
  is triggered.  Is the current write address of DMA1 different to the one
  during the last IRQ, then the data is passed to the demuxer.

  There is an additional DMA-IRQ-method: packet count IRQ. This isn't
  implemented correctly yet.

  The solution is to disable HW PID filtering, but I don't know how the DVB
  API software demux behaves on slow systems with 45MBit/s TS.

Solved bugs :)
--------------
1g) pid-filtering (somehow pid index 4 and 5 (EMM_PID and ECM_PID) aren't
working)
SOLUTION: also index 0 was affected, because net_translation is done for
these indexes by default

5b) isochronous transfer does only work in the first attempt (for the Sky2PC
USB, Air2PC is working) SOLUTION: the flexcop was going asleep and never really
woke up again (don't know if this need fixes, see
flexcop-fe-tuner.c:flexcop_sleep)

NEWS: when the driver is loaded and unloaded and loaded again (w/o doing
anything in the while the driver is loaded the first time), no transfers take
place anymore.

Improvements when rewriting (refactoring) is done
=================================================

- split sleeping of the flexcop (misc_204.ACPI3_sig = 1;) from lnb_control
  (enable sleeping for other demods than dvb-s)
- add support for CableStar (stv0297 Microtune 203x/ALPS) (almost done, incompatibilities with the Nexus-CA)

Debugging
---------
- add verbose debugging to skystar2.c (dump the reg_dw_data) and compare it
  with this flexcop, this is important, because i2c is now using the
  flexcop_ibi_value union from flexcop-reg.h (do you have a better idea for
  that, please tell us so).

Everything which is identical in the following table, can be put into a common
flexcop-module.

                  PCI                  USB
-------------------------------------------------------------------------------
Different:
Register access:  accessing IO memory  USB control message
I2C bus:          I2C bus of the FC    USB control message
Data transfer:    DMA                  isochronous transfer
EEPROM transfer:  through i2c bus      not clear yet

Identical:
Streaming:                 accessing registers
PID Filtering:             accessing registers
Sram destinations:         accessing registers
Tuner/Demod:                     I2C bus
DVB-stuff:            can be written for common use

Acknowledgements (just for the rewriting part)
================

Bjarne Steinsbo thought a lot in the first place of the pci part for this code
sharing idea.

Andreas Oberritter for providing a recent PCI initialization template
(pluto2.c).

Boleslaw Ciesielski for pointing out a problem with firmware loader.

Vadim Catana for correcting the USB transfer.

comments, critics and ideas to linux-dvb@linuxtv.org.