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Based on kernel version 3.9. Page generated on 2013-05-02 23:07 EST.

1	Kernel driver lm90
2	==================
3	
4	Supported chips:
5	  * National Semiconductor LM90
6	    Prefix: 'lm90'
7	    Addresses scanned: I2C 0x4c
8	    Datasheet: Publicly available at the National Semiconductor website
9	               http://www.national.com/pf/LM/LM90.html
10	  * National Semiconductor LM89
11	    Prefix: 'lm89' (no auto-detection)
12	    Addresses scanned: I2C 0x4c and 0x4d
13	    Datasheet: Publicly available at the National Semiconductor website
14	               http://www.national.com/mpf/LM/LM89.html
15	  * National Semiconductor LM99
16	    Prefix: 'lm99'
17	    Addresses scanned: I2C 0x4c and 0x4d
18	    Datasheet: Publicly available at the National Semiconductor website
19	               http://www.national.com/pf/LM/LM99.html
20	  * National Semiconductor LM86
21	    Prefix: 'lm86'
22	    Addresses scanned: I2C 0x4c
23	    Datasheet: Publicly available at the National Semiconductor website
24	               http://www.national.com/mpf/LM/LM86.html
25	  * Analog Devices ADM1032
26	    Prefix: 'adm1032'
27	    Addresses scanned: I2C 0x4c and 0x4d
28	    Datasheet: Publicly available at the ON Semiconductor website
29	               http://www.onsemi.com/PowerSolutions/product.do?id=ADM1032
30	  * Analog Devices ADT7461
31	    Prefix: 'adt7461'
32	    Addresses scanned: I2C 0x4c and 0x4d
33	    Datasheet: Publicly available at the ON Semiconductor website
34	               http://www.onsemi.com/PowerSolutions/product.do?id=ADT7461
35	  * Analog Devices ADT7461A
36	    Prefix: 'adt7461a'
37	    Addresses scanned: I2C 0x4c and 0x4d
38	    Datasheet: Publicly available at the ON Semiconductor website
39	               http://www.onsemi.com/PowerSolutions/product.do?id=ADT7461A
40	  * ON Semiconductor NCT1008
41	    Prefix: 'nct1008'
42	    Addresses scanned: I2C 0x4c and 0x4d
43	    Datasheet: Publicly available at the ON Semiconductor website
44	               http://www.onsemi.com/PowerSolutions/product.do?id=NCT1008
45	  * Maxim MAX6646
46	    Prefix: 'max6646'
47	    Addresses scanned: I2C 0x4d
48	    Datasheet: Publicly available at the Maxim website
49	               http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
50	  * Maxim MAX6647
51	    Prefix: 'max6646'
52	    Addresses scanned: I2C 0x4e
53	    Datasheet: Publicly available at the Maxim website
54	               http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
55	  * Maxim MAX6648
56	    Prefix: 'max6646'
57	    Addresses scanned: I2C 0x4c
58	    Datasheet: Publicly available at the Maxim website
59	               http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
60	  * Maxim MAX6649
61	    Prefix: 'max6646'
62	    Addresses scanned: I2C 0x4c
63	    Datasheet: Publicly available at the Maxim website
64	               http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
65	  * Maxim MAX6657
66	    Prefix: 'max6657'
67	    Addresses scanned: I2C 0x4c
68	    Datasheet: Publicly available at the Maxim website
69	               http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
70	  * Maxim MAX6658
71	    Prefix: 'max6657'
72	    Addresses scanned: I2C 0x4c
73	    Datasheet: Publicly available at the Maxim website
74	               http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
75	  * Maxim MAX6659
76	    Prefix: 'max6659'
77	    Addresses scanned: I2C 0x4c, 0x4d, 0x4e
78	    Datasheet: Publicly available at the Maxim website
79	               http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
80	  * Maxim MAX6680
81	    Prefix: 'max6680'
82	    Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
83	                           0x4c, 0x4d and 0x4e
84	    Datasheet: Publicly available at the Maxim website
85	               http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370
86	  * Maxim MAX6681
87	    Prefix: 'max6680'
88	    Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
89	                           0x4c, 0x4d and 0x4e
90	    Datasheet: Publicly available at the Maxim website
91	               http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370
92	  * Maxim MAX6692
93	    Prefix: 'max6646'
94	    Addresses scanned: I2C 0x4c
95	    Datasheet: Publicly available at the Maxim website
96	               http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
97	  * Maxim MAX6695
98	    Prefix: 'max6695'
99	    Addresses scanned: I2C 0x18
100	    Datasheet: Publicly available at the Maxim website
101	               http://www.maxim-ic.com/datasheet/index.mvp/id/4199
102	  * Maxim MAX6696
103	    Prefix: 'max6695'
104	    Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
105	                           0x4c, 0x4d and 0x4e
106	    Datasheet: Publicly available at the Maxim website
107	               http://www.maxim-ic.com/datasheet/index.mvp/id/4199
108	  * Winbond/Nuvoton W83L771W/G
109	    Prefix: 'w83l771'
110	    Addresses scanned: I2C 0x4c
111	    Datasheet: No longer available
112	  * Winbond/Nuvoton W83L771AWG/ASG
113	    Prefix: 'w83l771'
114	    Addresses scanned: I2C 0x4c
115	    Datasheet: Not publicly available, can be requested from Nuvoton
116	  * Philips/NXP SA56004X
117	    Prefix: 'sa56004'
118	    Addresses scanned: I2C 0x48 through 0x4F
119	    Datasheet: Publicly available at NXP website
120	               http://ics.nxp.com/products/interface/datasheet/sa56004x.pdf
121	  * GMT G781
122	    Prefix: 'g781'
123	    Addresses scanned: I2C 0x4c, 0x4d
124	    Datasheet: Not publicly available from GMT
125	
126	Author: Jean Delvare <khali@linux-fr.org>
127	
128	
129	Description
130	-----------
131	
132	The LM90 is a digital temperature sensor. It senses its own temperature as
133	well as the temperature of up to one external diode. It is compatible
134	with many other devices, many of which are supported by this driver.
135	
136	Note that there is no easy way to differentiate between the MAX6657,
137	MAX6658 and MAX6659 variants. The extra features of the MAX6659 are only
138	supported by this driver if the chip is located at address 0x4d or 0x4e,
139	or if the chip type is explicitly selected as max6659.
140	The MAX6680 and MAX6681 only differ in their pinout, therefore they obviously
141	can't (and don't need to) be distinguished.
142	
143	The specificity of this family of chipsets over the ADM1021/LM84
144	family is that it features critical limits with hysteresis, and an
145	increased resolution of the remote temperature measurement.
146	
147	The different chipsets of the family are not strictly identical, although
148	very similar. For reference, here comes a non-exhaustive list of specific
149	features:
150	
151	LM90:
152	  * Filter and alert configuration register at 0xBF.
153	  * ALERT is triggered by temperatures over critical limits.
154	
155	LM86 and LM89:
156	  * Same as LM90
157	  * Better external channel accuracy
158	
159	LM99:
160	  * Same as LM89
161	  * External temperature shifted by 16 degrees down
162	
163	ADM1032:
164	  * Consecutive alert register at 0x22.
165	  * Conversion averaging.
166	  * Up to 64 conversions/s.
167	  * ALERT is triggered by open remote sensor.
168	  * SMBus PEC support for Write Byte and Receive Byte transactions.
169	
170	ADT7461, ADT7461A, NCT1008:
171	  * Extended temperature range (breaks compatibility)
172	  * Lower resolution for remote temperature
173	
174	MAX6657 and MAX6658:
175	  * Better local resolution
176	  * Remote sensor type selection
177	
178	MAX6659:
179	  * Better local resolution
180	  * Selectable address
181	  * Second critical temperature limit
182	  * Remote sensor type selection
183	
184	MAX6680 and MAX6681:
185	  * Selectable address
186	  * Remote sensor type selection
187	
188	MAX6695 and MAX6696:
189	  * Better local resolution
190	  * Selectable address (max6696)
191	  * Second critical temperature limit
192	  * Two remote sensors
193	
194	W83L771W/G
195	  * The G variant is lead-free, otherwise similar to the W.
196	  * Filter and alert configuration register at 0xBF
197	  * Moving average (depending on conversion rate)
198	
199	W83L771AWG/ASG
200	  * Successor of the W83L771W/G, same features.
201	  * The AWG and ASG variants only differ in package format.
202	  * Diode ideality factor configuration (remote sensor) at 0xE3
203	
204	SA56004X:
205	  * Better local resolution
206	
207	All temperature values are given in degrees Celsius. Resolution
208	is 1.0 degree for the local temperature, 0.125 degree for the remote
209	temperature, except for the MAX6657, MAX6658 and MAX6659 which have a
210	resolution of 0.125 degree for both temperatures.
211	
212	Each sensor has its own high and low limits, plus a critical limit.
213	Additionally, there is a relative hysteresis value common to both critical
214	values. To make life easier to user-space applications, two absolute values
215	are exported, one for each channel, but these values are of course linked.
216	Only the local hysteresis can be set from user-space, and the same delta
217	applies to the remote hysteresis.
218	
219	The lm90 driver will not update its values more frequently than configured with
220	the update_interval attribute; reading them more often will do no harm, but will
221	return 'old' values.
222	
223	SMBus Alert Support
224	-------------------
225	
226	This driver has basic support for SMBus alert. When an alert is received,
227	the status register is read and the faulty temperature channel is logged.
228	
229	The Analog Devices chips (ADM1032, ADT7461 and ADT7461A) and ON
230	Semiconductor chips (NCT1008) do not implement the SMBus alert protocol
231	properly so additional care is needed: the ALERT output is disabled when
232	an alert is received, and is re-enabled only when the alarm is gone.
233	Otherwise the chip would block alerts from other chips in the bus as long
234	as the alarm is active.
235	
236	PEC Support
237	-----------
238	
239	The ADM1032 is the only chip of the family which supports PEC. It does
240	not support PEC on all transactions though, so some care must be taken.
241	
242	When reading a register value, the PEC byte is computed and sent by the
243	ADM1032 chip. However, in the case of a combined transaction (SMBus Read
244	Byte), the ADM1032 computes the CRC value over only the second half of
245	the message rather than its entirety, because it thinks the first half
246	of the message belongs to a different transaction. As a result, the CRC
247	value differs from what the SMBus master expects, and all reads fail.
248	
249	For this reason, the lm90 driver will enable PEC for the ADM1032 only if
250	the bus supports the SMBus Send Byte and Receive Byte transaction types.
251	These transactions will be used to read register values, instead of
252	SMBus Read Byte, and PEC will work properly.
253	
254	Additionally, the ADM1032 doesn't support SMBus Send Byte with PEC.
255	Instead, it will try to write the PEC value to the register (because the
256	SMBus Send Byte transaction with PEC is similar to a Write Byte transaction
257	without PEC), which is not what we want. Thus, PEC is explicitly disabled
258	on SMBus Send Byte transactions in the lm90 driver.
259	
260	PEC on byte data transactions represents a significant increase in bandwidth
261	usage (+33% for writes, +25% for reads) in normal conditions. With the need
262	to use two SMBus transaction for reads, this overhead jumps to +50%. Worse,
263	two transactions will typically mean twice as much delay waiting for
264	transaction completion, effectively doubling the register cache refresh time.
265	I guess reliability comes at a price, but it's quite expensive this time.
266	
267	So, as not everyone might enjoy the slowdown, PEC can be disabled through
268	sysfs. Just write 0 to the "pec" file and PEC will be disabled. Write 1
269	to that file to enable PEC again.
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