1The cx88 driver
2===============
3
4Author:  Gerd Hoffmann
5
6This is a v4l2 device driver for the cx2388x chip.
7
8
9Current status
10--------------
11
12video
13	- Works.
14	- Overlay isn't supported.
15
16audio
17	- Works. The TV standard detection is made by the driver, as the
18	  hardware has bugs to auto-detect.
19	- audio data dma (i.e. recording without loopback cable to the
20	  sound card) is supported via cx88-alsa.
21
22vbi
23	- Works.
24
25
26How to add support for new cards
27--------------------------------
28
29The driver needs some config info for the TV cards.  This stuff is in
30cx88-cards.c.  If the driver doesn't work well you likely need a new
31entry for your card in that file.  Check the kernel log (using dmesg)
32to see whenever the driver knows your card or not.  There is a line
33like this one:
34
35.. code-block:: none
36
37	cx8800[0]: subsystem: 0070:3400, board: Hauppauge WinTV \
38		34xxx models [card=1,autodetected]
39
40If your card is listed as "board: UNKNOWN/GENERIC" it is unknown to
41the driver.  What to do then?
42
431) Try upgrading to the latest snapshot, maybe it has been added
44   meanwhile.
452) You can try to create a new entry yourself, have a look at
46   cx88-cards.c.  If that worked, mail me your changes as unified
47   diff ("diff -u").
483) Or you can mail me the config information.  We need at least the
49   following information to add the card:
50
51     - the PCI Subsystem ID ("0070:3400" from the line above,
52       "lspci -v" output is fine too).
53     - the tuner type used by the card.  You can try to find one by
54       trial-and-error using the tuner=<n> insmod option.  If you
55       know which one the card has you can also have a look at the
56       list in CARDLIST.tuner
57
58Documentation missing at the cx88 datasheet
59-------------------------------------------
60
61MO_OUTPUT_FORMAT (0x310164)
62
63.. code-block:: none
64
65  Previous default from DScaler: 0x1c1f0008
66  Digit 8: 31-28
67  28: PREVREMOD = 1
68
69  Digit 7: 27-24 (0xc = 12 = b1100 )
70  27: COMBALT = 1
71  26: PAL_INV_PHASE
72    (DScaler apparently set this to 1, resulted in sucky picture)
73
74  Digits 6,5: 23-16
75  25-16: COMB_RANGE = 0x1f [default] (9 bits -> max 512)
76
77  Digit 4: 15-12
78  15: DISIFX = 0
79  14: INVCBF = 0
80  13: DISADAPT = 0
81  12: NARROWADAPT = 0
82
83  Digit 3: 11-8
84  11: FORCE2H
85  10: FORCEREMD
86  9: NCHROMAEN
87  8: NREMODEN
88
89  Digit 2: 7-4
90  7-6: YCORE
91  5-4: CCORE
92
93  Digit 1: 3-0
94  3: RANGE = 1
95  2: HACTEXT
96  1: HSFMT
97
980x47 is the sync byte for MPEG-2 transport stream packets.
99Datasheet incorrectly states to use 47 decimal. 188 is the length.
100All DVB compliant frontends output packets with this start code.
101
102Hauppauge WinTV cx88 IR information
103-----------------------------------
104
105The controls for the mux are GPIO [0,1] for source, and GPIO 2 for muting.
106
107====== ======== =================================================
108GPIO0  GPIO1
109====== ======== =================================================
110  0        0    TV Audio
111  1        0    FM radio
112  0        1    Line-In
113  1        1    Mono tuner bypass or CD passthru (tuner specific)
114====== ======== =================================================
115
116GPIO 16(I believe) is tied to the IR port (if present).
117
118
119From the data sheet:
120
121- Register 24'h20004  PCI Interrupt Status
122
123 - bit [18]  IR_SMP_INT Set when 32 input samples have been collected over
124 - gpio[16] pin into GP_SAMPLE register.
125
126What's missing from the data sheet:
127
128- Setup 4KHz sampling rate (roughly 2x oversampled; good enough for our RC5
129  compat remote)
130- set register 0x35C050 to  0xa80a80
131- enable sampling
132- set register 0x35C054 to 0x5
133- enable the IRQ bit 18 in the interrupt mask register (and
134  provide for a handler)
135
136GP_SAMPLE register is at 0x35C058
137
138Bits are then right shifted into the GP_SAMPLE register at the specified
139rate; you get an interrupt when a full DWORD is received.
140You need to recover the actual RC5 bits out of the (oversampled) IR sensor
141bits. (Hint: look for the 0/1and 1/0 crossings of the RC5 bi-phase data)  An
142actual raw RC5 code will span 2-3 DWORDS, depending on the actual alignment.
143
144I'm pretty sure when no IR signal is present the receiver is always in a
145marking state(1); but stray light, etc can cause intermittent noise values
146as well.  Remember, this is a free running sample of the IR receiver state
147over time, so don't assume any sample starts at any particular place.
148
149Additional info
150~~~~~~~~~~~~~~~
151
152This data sheet (google search) seems to have a lovely description of the
153RC5 basics:
154http://www.atmel.com/dyn/resources/prod_documents/doc2817.pdf
155
156This document has more data:
157http://www.nenya.be/beor/electronics/rc5.htm
158
159This document has a  how to decode a bi-phase data stream:
160http://www.ee.washington.edu/circuit_archive/text/ir_decode.txt
161
162This document has still more info:
163http://www.xs4all.nl/~sbp/knowledge/ir/rc5.htm
164