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Based on kernel version 3.13. Page generated on 2014-01-20 22:05 EST.

1	
2				 SN9C1xx PC Camera Controllers
3					Driver for Linux
4				 =============================
5	
6				       - Documentation -
7	
8	
9	Index
10	=====
11	1.  Copyright
12	2.  Disclaimer
13	3.  License
14	4.  Overview and features
15	5.  Module dependencies
16	6.  Module loading
17	7.  Module parameters
18	8.  Optional device control through "sysfs"
19	9.  Supported devices
20	10. Notes for V4L2 application developers
21	11. Video frame formats
22	12. Contact information
23	13. Credits
24	
25	
26	1. Copyright
27	============
28	Copyright (C) 2004-2007 by Luca Risolia <luca.risolia@studio.unibo.it>
29	
30	
31	2. Disclaimer
32	=============
33	SONiX is a trademark of SONiX Technology Company Limited, inc.
34	This software is not sponsored or developed by SONiX.
35	
36	
37	3. License
38	==========
39	This program is free software; you can redistribute it and/or modify
40	it under the terms of the GNU General Public License as published by
41	the Free Software Foundation; either version 2 of the License, or
42	(at your option) any later version.
43	
44	This program is distributed in the hope that it will be useful,
45	but WITHOUT ANY WARRANTY; without even the implied warranty of
46	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
47	GNU General Public License for more details.
48	
49	You should have received a copy of the GNU General Public License
50	along with this program; if not, write to the Free Software
51	Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
52	
53	
54	4. Overview and features
55	========================
56	This driver attempts to support the video interface of the devices assembling
57	the SONiX SN9C101, SN9C102, SN9C103, SN9C105 and SN9C120 PC Camera Controllers
58	("SN9C1xx" from now on).
59	
60	The driver relies on the Video4Linux2 and USB core modules. It has been
61	designed to run properly on SMP systems as well.
62	
63	The latest version of the SN9C1xx driver can be found at the following URL:
64	http://www.linux-projects.org/
65	
66	Some of the features of the driver are:
67	
68	- full compliance with the Video4Linux2 API (see also "Notes for V4L2
69	  application developers" paragraph);
70	- available mmap or read/poll methods for video streaming through isochronous
71	  data transfers;
72	- automatic detection of image sensor;
73	- support for built-in microphone interface;
74	- support for any window resolutions and optional panning within the maximum
75	  pixel area of image sensor;
76	- image downscaling with arbitrary scaling factors from 1, 2 and 4 in both
77	  directions (see "Notes for V4L2 application developers" paragraph);
78	- two different video formats for uncompressed or compressed data in low or
79	  high compression quality (see also "Notes for V4L2 application developers"
80	  and "Video frame formats" paragraphs);
81	- full support for the capabilities of many of the possible image sensors that
82	  can be connected to the SN9C1xx bridges, including, for instance, red, green,
83	  blue and global gain adjustments and exposure (see "Supported devices"
84	  paragraph for details);
85	- use of default color settings for sunlight conditions;
86	- dynamic I/O interface for both SN9C1xx and image sensor control and
87	  monitoring (see "Optional device control through 'sysfs'" paragraph);
88	- dynamic driver control thanks to various module parameters (see "Module
89	  parameters" paragraph);
90	- up to 64 cameras can be handled at the same time; they can be connected and
91	  disconnected from the host many times without turning off the computer, if
92	  the system supports hotplugging;
93	- no known bugs.
94	
95	
96	5. Module dependencies
97	======================
98	For it to work properly, the driver needs kernel support for Video4Linux and
99	USB.
100	
101	The following options of the kernel configuration file must be enabled and
102	corresponding modules must be compiled:
103	
104		# Multimedia devices
105		#
106		CONFIG_VIDEO_DEV=m
107	
108	To enable advanced debugging functionality on the device through /sysfs:
109	
110		# Multimedia devices
111		#
112		CONFIG_VIDEO_ADV_DEBUG=y
113	
114		# USB support
115		#
116		CONFIG_USB=m
117	
118	In addition, depending on the hardware being used, the modules below are
119	necessary:
120	
121		# USB Host Controller Drivers
122		#
123		CONFIG_USB_EHCI_HCD=m
124		CONFIG_USB_UHCI_HCD=m
125		CONFIG_USB_OHCI_HCD=m
126	
127	The SN9C103, SN9c105 and SN9C120 controllers also provide a built-in microphone
128	interface. It is supported by the USB Audio driver thanks to the ALSA API:
129	
130		# Sound
131		#
132		CONFIG_SOUND=y
133	
134		# Advanced Linux Sound Architecture
135		#
136		CONFIG_SND=m
137	
138		# USB devices
139		#
140		CONFIG_SND_USB_AUDIO=m
141	
142	And finally:
143	
144		# USB Multimedia devices
145		#
146		CONFIG_USB_SN9C102=m
147	
148	
149	6. Module loading
150	=================
151	To use the driver, it is necessary to load the "sn9c102" module into memory
152	after every other module required: "videodev", "v4l2_common", "compat_ioctl32",
153	"usbcore" and, depending on the USB host controller you have, "ehci-hcd",
154	"uhci-hcd" or "ohci-hcd".
155	
156	Loading can be done as shown below:
157	
158		[root@localhost home]# modprobe sn9c102
159	
160	Note that the module is called "sn9c102" for historic reasons, although it
161	does not just support the SN9C102.
162	
163	At this point all the devices supported by the driver and connected to the USB
164	ports should be recognized. You can invoke "dmesg" to analyze kernel messages
165	and verify that the loading process has gone well:
166	
167		[user@localhost home]$ dmesg
168	
169	or, to isolate all the kernel messages generated by the driver:
170	
171		[user@localhost home]$ dmesg | grep sn9c102
172	
173	
174	7. Module parameters
175	====================
176	Module parameters are listed below:
177	-------------------------------------------------------------------------------
178	Name:           video_nr
179	Type:           short array (min = 0, max = 64)
180	Syntax:         <-1|n[,...]>
181	Description:    Specify V4L2 minor mode number:
182			-1 = use next available
183			 n = use minor number n
184			You can specify up to 64 cameras this way.
185			For example:
186			video_nr=-1,2,-1 would assign minor number 2 to the second
187			recognized camera and use auto for the first one and for every
188			other camera.
189	Default:        -1
190	-------------------------------------------------------------------------------
191	Name:           force_munmap
192	Type:           bool array (min = 0, max = 64)
193	Syntax:         <0|1[,...]>
194	Description:    Force the application to unmap previously mapped buffer memory
195			before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not
196			all the applications support this feature. This parameter is
197			specific for each detected camera.
198			0 = do not force memory unmapping
199			1 = force memory unmapping (save memory)
200	Default:        0
201	-------------------------------------------------------------------------------
202	Name:           frame_timeout
203	Type:           uint array (min = 0, max = 64)
204	Syntax:         <0|n[,...]>
205	Description:    Timeout for a video frame in seconds before returning an I/O
206			error; 0 for infinity. This parameter is specific for each
207			detected camera and can be changed at runtime thanks to the
208			/sys filesystem interface.
209	Default:        2
210	-------------------------------------------------------------------------------
211	Name:           debug
212	Type:           ushort
213	Syntax:         <n>
214	Description:    Debugging information level, from 0 to 3:
215			0 = none (use carefully)
216			1 = critical errors
217			2 = significant information
218			3 = more verbose messages
219			Level 3 is useful for testing only. It also shows some more
220			information about the hardware being detected.
221			This parameter can be changed at runtime thanks to the /sys
222			filesystem interface.
223	Default:        2
224	-------------------------------------------------------------------------------
225	
226	
227	8. Optional device control through "sysfs" [1]
228	==========================================
229	If the kernel has been compiled with the CONFIG_VIDEO_ADV_DEBUG option enabled,
230	it is possible to read and write both the SN9C1xx and the image sensor
231	registers by using the "sysfs" filesystem interface.
232	
233	Every time a supported device is recognized, a write-only file named "green" is
234	created in the /sys/class/video4linux/videoX directory. You can set the green
235	channel's gain by writing the desired value to it. The value may range from 0
236	to 15 for the SN9C101 or SN9C102 bridges, from 0 to 127 for the SN9C103,
237	SN9C105 and SN9C120 bridges.
238	Similarly, only for the SN9C103, SN9C105 and SN9C120 controllers, blue and red
239	gain control files are available in the same directory, for which accepted
240	values may range from 0 to 127.
241	
242	There are other four entries in the directory above for each registered camera:
243	"reg", "val", "i2c_reg" and "i2c_val". The first two files control the
244	SN9C1xx bridge, while the other two control the sensor chip. "reg" and
245	"i2c_reg" hold the values of the current register index where the following
246	reading/writing operations are addressed at through "val" and "i2c_val". Their
247	use is not intended for end-users. Note that "i2c_reg" and "i2c_val" will not
248	be created if the sensor does not actually support the standard I2C protocol or
249	its registers are not 8-bit long. Also, remember that you must be logged in as
250	root before writing to them.
251	
252	As an example, suppose we were to want to read the value contained in the
253	register number 1 of the sensor register table - which is usually the product
254	identifier - of the camera registered as "/dev/video0":
255	
256		[root@localhost #] cd /sys/class/video4linux/video0
257		[root@localhost #] echo 1 > i2c_reg
258		[root@localhost #] cat i2c_val
259	
260	Note that "cat" will fail if sensor registers cannot be read.
261	
262	Now let's set the green gain's register of the SN9C101 or SN9C102 chips to 2:
263	
264		[root@localhost #] echo 0x11 > reg
265		[root@localhost #] echo 2 > val
266	
267	Note that the SN9C1xx always returns 0 when some of its registers are read.
268	To avoid race conditions, all the I/O accesses to the above files are
269	serialized.
270	The sysfs interface also provides the "frame_header" entry, which exports the
271	frame header of the most recent requested and captured video frame. The header
272	is always 18-bytes long and is appended to every video frame by the SN9C1xx
273	controllers. As an example, this additional information can be used by the user
274	application for implementing auto-exposure features via software.
275	
276	The following table describes the frame header exported by the SN9C101 and
277	SN9C102:
278	
279	Byte #  Value or bits Description
280	------  ------------- -----------
281	0x00    0xFF          Frame synchronisation pattern
282	0x01    0xFF          Frame synchronisation pattern
283	0x02    0x00          Frame synchronisation pattern
284	0x03    0xC4          Frame synchronisation pattern
285	0x04    0xC4          Frame synchronisation pattern
286	0x05    0x96          Frame synchronisation pattern
287	0x06    [3:0]         Read channel gain control = (1+R_GAIN/8)
288		[7:4]         Blue channel gain control = (1+B_GAIN/8)
289	0x07    [ 0 ]         Compression mode. 0=No compression, 1=Compression enabled
290		[2:1]         Maximum scale factor for compression
291		[ 3 ]         1 = USB fifo(2K bytes) is full
292		[ 4 ]         1 = Digital gain is finish
293		[ 5 ]         1 = Exposure is finish
294		[7:6]         Frame index
295	0x08    [7:0]         Y sum inside Auto-Exposure area (low-byte)
296	0x09    [7:0]         Y sum inside Auto-Exposure area (high-byte)
297			      where Y sum = (R/4 + 5G/16 + B/8) / 32
298	0x0A    [7:0]         Y sum outside Auto-Exposure area (low-byte)
299	0x0B    [7:0]         Y sum outside Auto-Exposure area (high-byte)
300			      where Y sum = (R/4 + 5G/16 + B/8) / 128
301	0x0C    0xXX          Not used
302	0x0D    0xXX          Not used
303	0x0E    0xXX          Not used
304	0x0F    0xXX          Not used
305	0x10    0xXX          Not used
306	0x11    0xXX          Not used
307	
308	The following table describes the frame header exported by the SN9C103:
309	
310	Byte #  Value or bits Description
311	------  ------------- -----------
312	0x00    0xFF          Frame synchronisation pattern
313	0x01    0xFF          Frame synchronisation pattern
314	0x02    0x00          Frame synchronisation pattern
315	0x03    0xC4          Frame synchronisation pattern
316	0x04    0xC4          Frame synchronisation pattern
317	0x05    0x96          Frame synchronisation pattern
318	0x06    [6:0]         Read channel gain control = (1/2+R_GAIN/64)
319	0x07    [6:0]         Blue channel gain control = (1/2+B_GAIN/64)
320		[7:4]
321	0x08    [ 0 ]         Compression mode. 0=No compression, 1=Compression enabled
322		[2:1]         Maximum scale factor for compression
323		[ 3 ]         1 = USB fifo(2K bytes) is full
324		[ 4 ]         1 = Digital gain is finish
325		[ 5 ]         1 = Exposure is finish
326		[7:6]         Frame index
327	0x09    [7:0]         Y sum inside Auto-Exposure area (low-byte)
328	0x0A    [7:0]         Y sum inside Auto-Exposure area (high-byte)
329			      where Y sum = (R/4 + 5G/16 + B/8) / 32
330	0x0B    [7:0]         Y sum outside Auto-Exposure area (low-byte)
331	0x0C    [7:0]         Y sum outside Auto-Exposure area (high-byte)
332			      where Y sum = (R/4 + 5G/16 + B/8) / 128
333	0x0D    [1:0]         Audio frame number
334		[ 2 ]         1 = Audio is recording
335	0x0E    [7:0]         Audio summation (low-byte)
336	0x0F    [7:0]         Audio summation (high-byte)
337	0x10    [7:0]         Audio sample count
338	0x11    [7:0]         Audio peak data in audio frame
339	
340	The AE area (sx, sy, ex, ey) in the active window can be set by programming the
341	registers 0x1c, 0x1d, 0x1e and 0x1f of the SN9C1xx controllers, where one unit
342	corresponds to 32 pixels.
343	
344	[1] The frame headers exported by the SN9C105 and SN9C120 are not described.
345	
346	
347	9. Supported devices
348	====================
349	None of the names of the companies as well as their products will be mentioned
350	here. They have never collaborated with the author, so no advertising.
351	
352	From the point of view of a driver, what unambiguously identify a device are
353	its vendor and product USB identifiers. Below is a list of known identifiers of
354	devices assembling the SN9C1xx PC camera controllers:
355	
356	Vendor ID  Product ID
357	---------  ----------
358	0x0458     0x7025
359	0x045e     0x00f5
360	0x045e     0x00f7
361	0x0471     0x0327
362	0x0471     0x0328
363	0x0c45     0x6001
364	0x0c45     0x6005
365	0x0c45     0x6007
366	0x0c45     0x6009
367	0x0c45     0x600d
368	0x0c45     0x6011
369	0x0c45     0x6019
370	0x0c45     0x6024
371	0x0c45     0x6025
372	0x0c45     0x6028
373	0x0c45     0x6029
374	0x0c45     0x602a
375	0x0c45     0x602b
376	0x0c45     0x602c
377	0x0c45     0x602d
378	0x0c45     0x602e
379	0x0c45     0x6030
380	0x0c45     0x603f
381	0x0c45     0x6080
382	0x0c45     0x6082
383	0x0c45     0x6083
384	0x0c45     0x6088
385	0x0c45     0x608a
386	0x0c45     0x608b
387	0x0c45     0x608c
388	0x0c45     0x608e
389	0x0c45     0x608f
390	0x0c45     0x60a0
391	0x0c45     0x60a2
392	0x0c45     0x60a3
393	0x0c45     0x60a8
394	0x0c45     0x60aa
395	0x0c45     0x60ab
396	0x0c45     0x60ac
397	0x0c45     0x60ae
398	0x0c45     0x60af
399	0x0c45     0x60b0
400	0x0c45     0x60b2
401	0x0c45     0x60b3
402	0x0c45     0x60b8
403	0x0c45     0x60ba
404	0x0c45     0x60bb
405	0x0c45     0x60bc
406	0x0c45     0x60be
407	0x0c45     0x60c0
408	0x0c45     0x60c2
409	0x0c45     0x60c8
410	0x0c45     0x60cc
411	0x0c45     0x60ea
412	0x0c45     0x60ec
413	0x0c45     0x60ef
414	0x0c45     0x60fa
415	0x0c45     0x60fb
416	0x0c45     0x60fc
417	0x0c45     0x60fe
418	0x0c45     0x6102
419	0x0c45     0x6108
420	0x0c45     0x610f
421	0x0c45     0x6130
422	0x0c45     0x6138
423	0x0c45     0x613a
424	0x0c45     0x613b
425	0x0c45     0x613c
426	0x0c45     0x613e
427	
428	The list above does not imply that all those devices work with this driver: up
429	until now only the ones that assemble the following pairs of SN9C1xx bridges
430	and image sensors are supported; kernel messages will always tell you whether
431	this is the case (see "Module loading" paragraph):
432	
433	Image sensor / SN9C1xx bridge      | SN9C10[12]  SN9C103  SN9C105  SN9C120
434	-------------------------------------------------------------------------------
435	HV7131D    Hynix Semiconductor     | Yes         No       No       No
436	HV7131R    Hynix Semiconductor     | No          Yes      Yes      Yes
437	MI-0343    Micron Technology       | Yes         No       No       No
438	MI-0360    Micron Technology       | No          Yes      Yes      Yes
439	OV7630     OmniVision Technologies | Yes         Yes      Yes      Yes
440	OV7660     OmniVision Technologies | No          No       Yes      Yes
441	PAS106B    PixArt Imaging          | Yes         No       No       No
442	PAS202B    PixArt Imaging          | Yes         Yes      No       No
443	TAS5110C1B Taiwan Advanced Sensor  | Yes         No       No       No
444	TAS5110D   Taiwan Advanced Sensor  | Yes         No       No       No
445	TAS5130D1B Taiwan Advanced Sensor  | Yes         No       No       No
446	
447	"Yes" means that the pair is supported by the driver, while "No" means that the
448	pair does not exist or is not supported by the driver.
449	
450	Only some of the available control settings of each image sensor are supported
451	through the V4L2 interface.
452	
453	Donations of new models for further testing and support would be much
454	appreciated. Non-available hardware will not be supported by the author of this
455	driver.
456	
457	
458	10. Notes for V4L2 application developers
459	=========================================
460	This driver follows the V4L2 API specifications. In particular, it enforces two
461	rules:
462	
463	- exactly one I/O method, either "mmap" or "read", is associated with each
464	file descriptor. Once it is selected, the application must close and reopen the
465	device to switch to the other I/O method;
466	
467	- although it is not mandatory, previously mapped buffer memory should always
468	be unmapped before calling any "VIDIOC_S_CROP" or "VIDIOC_S_FMT" ioctl's.
469	The same number of buffers as before will be allocated again to match the size
470	of the new video frames, so you have to map the buffers again before any I/O
471	attempts on them.
472	
473	Consistently with the hardware limits, this driver also supports image
474	downscaling with arbitrary scaling factors from 1, 2 and 4 in both directions.
475	However, the V4L2 API specifications don't correctly define how the scaling
476	factor can be chosen arbitrarily by the "negotiation" of the "source" and
477	"target" rectangles. To work around this flaw, we have added the convention
478	that, during the negotiation, whenever the "VIDIOC_S_CROP" ioctl is issued, the
479	scaling factor is restored to 1.
480	
481	This driver supports two different video formats: the first one is the "8-bit
482	Sequential Bayer" format and can be used to obtain uncompressed video data
483	from the device through the current I/O method, while the second one provides
484	either "raw" compressed video data (without frame headers not related to the
485	compressed data) or standard JPEG (with frame headers). The compression quality
486	may vary from 0 to 1 and can be selected or queried thanks to the
487	VIDIOC_S_JPEGCOMP and VIDIOC_G_JPEGCOMP V4L2 ioctl's. For maximum flexibility,
488	both the default active video format and the default compression quality
489	depend on how the image sensor being used is initialized.
490	
491	
492	11. Video frame formats [1]
493	=======================
494	The SN9C1xx PC Camera Controllers can send images in two possible video
495	formats over the USB: either native "Sequential RGB Bayer" or compressed.
496	The compression is used to achieve high frame rates. With regard to the
497	SN9C101, SN9C102 and SN9C103, the compression is based on the Huffman encoding
498	algorithm described below, while with regard to the SN9C105 and SN9C120 the
499	compression is based on the JPEG standard.
500	The current video format may be selected or queried from the user application
501	by calling the VIDIOC_S_FMT or VIDIOC_G_FMT ioctl's, as described in the V4L2
502	API specifications.
503	
504	The name "Sequential Bayer" indicates the organization of the red, green and
505	blue pixels in one video frame. Each pixel is associated with a 8-bit long
506	value and is disposed in memory according to the pattern shown below:
507	
508	B[0]   G[1]    B[2]    G[3]    ...   B[m-2]         G[m-1]
509	G[m]   R[m+1]  G[m+2]  R[m+2]  ...   G[2m-2]        R[2m-1]
510	...
511	...                                  B[(n-1)(m-2)]  G[(n-1)(m-1)]
512	...                                  G[n(m-2)]      R[n(m-1)]
513	
514	The above matrix also represents the sequential or progressive read-out mode of
515	the (n, m) Bayer color filter array used in many CCD or CMOS image sensors.
516	
517	The Huffman compressed video frame consists of a bitstream that encodes for
518	every R, G, or B pixel the difference between the value of the pixel itself and
519	some reference pixel value. Pixels are organised in the Bayer pattern and the
520	Bayer sub-pixels are tracked individually and alternatingly. For example, in
521	the first line values for the B and G1 pixels are alternatingly encoded, while
522	in the second line values for the G2 and R pixels are alternatingly encoded.
523	
524	The pixel reference value is calculated as follows:
525	- the 4 top left pixels are encoded in raw uncompressed 8-bit format;
526	- the value in the top two rows is the value of the pixel left of the current
527	  pixel;
528	- the value in the left column is the value of the pixel above the current
529	  pixel;
530	- for all other pixels, the reference value is the average of the value of the
531	  pixel on the left and the value of the pixel above the current pixel;
532	- there is one code in the bitstream that specifies the value of a pixel
533	  directly (in 4-bit resolution);
534	- pixel values need to be clamped inside the range [0..255] for proper
535	  decoding.
536	
537	The algorithm purely describes the conversion from compressed Bayer code used
538	in the SN9C101, SN9C102 and SN9C103 chips to uncompressed Bayer. Additional
539	steps are required to convert this to a color image (i.e. a color interpolation
540	algorithm).
541	
542	The following Huffman codes have been found:
543	0: +0 (relative to reference pixel value)
544	100: +4
545	101: -4?
546	1110xxxx: set absolute value to xxxx.0000
547	1101: +11
548	1111: -11
549	11001: +20
550	110000: -20
551	110001: ??? - these codes are apparently not used
552	
553	[1] The Huffman compression algorithm has been reverse-engineered and
554	    documented by Bertrik Sikken.
555	
556	
557	12. Contact information
558	=======================
559	The author may be contacted by e-mail at <luca.risolia@studio.unibo.it>.
560	
561	GPG/PGP encrypted e-mail's are accepted. The GPG key ID of the author is
562	'FCE635A4'; the public 1024-bit key should be available at any keyserver;
563	the fingerprint is: '88E8 F32F 7244 68BA 3958  5D40 99DA 5D2A FCE6 35A4'.
564	
565	
566	13. Credits
567	===========
568	Many thanks to following persons for their contribute (listed in alphabetical
569	order):
570	
571	- David Anderson for the donation of a webcam;
572	- Luca Capello for the donation of a webcam;
573	- Philippe Coval for having helped testing the PAS202BCA image sensor;
574	- Joao Rodrigo Fuzaro, Joao Limirio, Claudio Filho and Caio Begotti for the
575	  donation of a webcam;
576	- Dennis Heitmann for the donation of a webcam;
577	- Jon Hollstrom for the donation of a webcam;
578	- Nick McGill for the donation of a webcam;
579	- Carlos Eduardo Medaglia Dyonisio, who added the support for the PAS202BCB
580	  image sensor;
581	- Stefano Mozzi, who donated 45 EU;
582	- Andrew Pearce for the donation of a webcam;
583	- John Pullan for the donation of a webcam;
584	- Bertrik Sikken, who reverse-engineered and documented the Huffman compression
585	  algorithm used in the SN9C101, SN9C102 and SN9C103 controllers and
586	  implemented the first decoder;
587	- Ronny Standke for the donation of a webcam;
588	- Mizuno Takafumi for the donation of a webcam;
589	- an "anonymous" donator (who didn't want his name to be revealed) for the
590	  donation of a webcam.
591	- an anonymous donator for the donation of four webcams and two boards with ten
592	  image sensors.
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