Documentation/hwmon/pmbus-core.rst

8 [from pmbus.org] The Power Management Bus (PMBus) is an open standard
9 power-management protocol with a fully defined command language that facilitates
11 protocol is implemented over the industry-standard SMBus serial interface and
12 enables programming, control, and real-time monitoring of compliant power
13 conversion products. This flexible and highly versatile standard allows for
17 semiconductor companies, this open power system standard is maintained and
18 promoted by the PMBus Implementers Forum (PMBus-IF), comprising 30+ adopters
22 commands, and manufacturers can add as many non-standard commands as they like.
23 Also, different PMBUs devices act differently if non-supported commands are
43 PMBus device capabilities auto-detection
46 For generic PMBus devices, code in pmbus.c attempts to auto-detect all supported
47 PMBus commands. Auto-detection is somewhat limited, since there are simply too
50 pages (see the PMBus specification for details on multi-page PMBus devices).
53 all commands can be auto-detected. The data structures in this driver can be
57 Some commands are always auto-detected. This applies to all limit commands
59 Limits and alarm attributes are auto-detected because there are simply too many
67 standard PMBus commands and virtual PMBus commands.
69 Standard PMBus commands
70 -----------------------
72 Standard PMBus commands (commands values 0x00 to 0xff) are defined in the PMBUs
76 ----------------------
78 Virtual PMBus commands are provided to enable support for non-standard
83 distinguished from standard PMBus commands (which can not have values larger
92 - READ commands are read-only; writes are either ignored or return an error.
93 - RESET commands are read/write. Reading reset registers returns zero
98 code returns non-negative values if a virtual command is supported, or a
99 negative error code if not. The chip driver may return -ENODATA or any other
100 Linux error code in this case, though an error code other than -ENODATA is
107 ------------------------
113 - For devices supporting its data in Direct Data Format, it provides coefficients
116 - Supported chip functionality can be provided to the core driver. This may be
117   necessary for chips which react badly if non-supported commands are executed,
119 - Several function entry points are provided to support overriding and/or
121   non-standard PMBus commands to standard commands, or to augment standard
137 ---------------------------------
140 successful. A return value of -ENODATA indicates that there is no manufacturer
141 specific command, but that a standard PMBus command may exist. Any other
143 chip, and that no attempt should be made to read or write the standard
154 		if (status != -ENODATA)
158 		return -EINVAL;
169 <page> may be -1, which means "current page".
193 <page> may be -1, which means "current page".
201 pre-determined. It is currently only used by the generic pmbus driver
205 ---------------------------------
245 selects page first. <page> may be -1, which means "current page".
252 selects page first. <page> may be -1, which means "current page".
284 Execute probe function. Similar to standard probe function for other drivers,
321 -----
335 Some i2c controllers do not support single-byte commands (write commands with
342 by the standard WRITE_PROTECT command.