The main motivation for this series is patch 4: switching to
"controller/master" when defining the I2C terminology. This sets the
base for further improvements to inclusive language within the Linux
Kernel. The other patches are improvements found on the way.
Changes since v2:
* improve patch 6 to be more clear wrt to the synonyms 'adapter/client'
* fix the faulty 'drivers/media/gpio' path
* slight rewording in patches 4 and 5
Wolfram Sang (6):
docs: i2c: summary: start sentences consistently.
docs: i2c: summary: update I2C specification link
docs: i2c: summary: update speed mode description
docs: i2c: summary: document use of inclusive language
docs: i2c: summary: document 'local' and 'remote' targets
docs: i2c: summary: be clearer with 'controller/target' and
'adapter/client' pairs
Documentation/i2c/i2c_bus.svg | 15 +++----
Documentation/i2c/summary.rst | 79 ++++++++++++++++++++++-------------
2 files changed, 58 insertions(+), 36 deletions(-)
--
2.43.0
Change the first paragraphs to contain only one space after the end of
the previous sentence like in the rest of the document.
Signed-off-by: Wolfram Sang <[email protected]>
Reviewed-by: Easwar Hariharan <[email protected]>
---
Documentation/i2c/summary.rst | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/Documentation/i2c/summary.rst b/Documentation/i2c/summary.rst
index 786c618ba3be..28ff80a2302b 100644
--- a/Documentation/i2c/summary.rst
+++ b/Documentation/i2c/summary.rst
@@ -4,10 +4,10 @@ Introduction to I2C and SMBus
I²C (pronounce: I squared C and written I2C in the kernel documentation) is
a protocol developed by Philips. It is a slow two-wire protocol (variable
-speed, up to 400 kHz), with a high speed extension (3.4 MHz). It provides
+speed, up to 400 kHz), with a high speed extension (3.4 MHz). It provides
an inexpensive bus for connecting many types of devices with infrequent or
-low bandwidth communications needs. I2C is widely used with embedded
-systems. Some systems use variants that don't meet branding requirements,
+low bandwidth communications needs. I2C is widely used with embedded
+systems. Some systems use variants that don't meet branding requirements,
and so are not advertised as being I2C but come under different names,
e.g. TWI (Two Wire Interface), IIC.
@@ -18,14 +18,14 @@ access the PDF. An older version of the specification (revision 6) is archived
`here <https://web.archive.org/web/20210813122132/https://www.nxp.com/docs/en/user-guide/UM10204.pdf>`_.
SMBus (System Management Bus) is based on the I2C protocol, and is mostly
-a subset of I2C protocols and signaling. Many I2C devices will work on an
+a subset of I2C protocols and signaling. Many I2C devices will work on an
SMBus, but some SMBus protocols add semantics beyond what is required to
-achieve I2C branding. Modern PC mainboards rely on SMBus. The most common
+achieve I2C branding. Modern PC mainboards rely on SMBus. The most common
devices connected through SMBus are RAM modules configured using I2C EEPROMs,
and hardware monitoring chips.
Because the SMBus is mostly a subset of the generalized I2C bus, we can
-use its protocols on many I2C systems. However, there are systems that don't
+use its protocols on many I2C systems. However, there are systems that don't
meet both SMBus and I2C electrical constraints; and others which can't
implement all the common SMBus protocol semantics or messages.
--
2.43.0
We now have the updated I2C specs and our own Code of Conduct, so we
have all we need to switch over to the inclusive terminology. Define
them here.
Signed-off-by: Wolfram Sang <[email protected]>
---
Documentation/i2c/i2c_bus.svg | 15 ++++++++-------
Documentation/i2c/summary.rst | 23 +++++++++++++++++------
2 files changed, 25 insertions(+), 13 deletions(-)
diff --git a/Documentation/i2c/i2c_bus.svg b/Documentation/i2c/i2c_bus.svg
index 3170de976373..45801de4af7d 100644
--- a/Documentation/i2c/i2c_bus.svg
+++ b/Documentation/i2c/i2c_bus.svg
@@ -1,5 +1,6 @@
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!-- Created with Inkscape (http://www.inkscape.org/) -->
+<!-- Updated to inclusive terminology by Wolfram Sang -->
<svg
xmlns:dc="http://purl.org/dc/elements/1.1/"
@@ -1120,7 +1121,7 @@
<rect
style="opacity:1;fill:#ffb9b9;fill-opacity:1;stroke:#f00000;stroke-width:2.8125;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1"
id="rect4424-3-2-9-7"
- width="112.5"
+ width="134.5"
height="113.75008"
x="112.5"
y="471.11221"
@@ -1133,15 +1134,15 @@
y="521.46259"
id="text4349"><tspan
sodipodi:role="line"
- x="167.5354"
+ x="178.5354"
y="521.46259"
style="font-size:25px;line-height:1.25;font-family:sans-serif;text-align:center;text-anchor:middle"
id="tspan1273">I2C</tspan><tspan
sodipodi:role="line"
- x="167.5354"
+ x="178.5354"
y="552.71259"
style="font-size:25px;line-height:1.25;font-family:sans-serif;text-align:center;text-anchor:middle"
- id="tspan1285">Master</tspan></text>
+ id="tspan1285">Controller</tspan></text>
<rect
style="color:#000000;clip-rule:nonzero;display:inline;overflow:visible;visibility:visible;opacity:1;isolation:auto;mix-blend-mode:normal;color-interpolation:sRGB;color-interpolation-filters:linearRGB;solid-color:#000000;solid-opacity:1;fill:#b9ffb9;fill-opacity:1;fill-rule:nonzero;stroke:#006400;stroke-width:2.8125;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;color-rendering:auto;image-rendering:auto;shape-rendering:auto;text-rendering:auto;enable-background:accumulate"
id="rect4424-3-2-9-7-3-3-5-3"
@@ -1171,7 +1172,7 @@
x="318.59131"
y="552.08752"
style="font-size:25.00000191px;line-height:1.25;font-family:sans-serif;text-align:center;text-anchor:middle;stroke-width:1px"
- id="tspan1287">Slave</tspan></text>
+ id="tspan1287">Target</tspan></text>
<path
style="fill:none;fill-rule:evenodd;stroke:#000000;stroke-width:1.99968767;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1"
d="m 112.49995,677.36223 c 712.50005,0 712.50005,0 712.50005,0"
@@ -1233,7 +1234,7 @@
x="468.59131"
y="552.08746"
style="font-size:25.00000191px;line-height:1.25;font-family:sans-serif;text-align:center;text-anchor:middle;stroke-width:1px"
- id="tspan1287-6">Slave</tspan></text>
+ id="tspan1287-6">Target</tspan></text>
<rect
style="color:#000000;clip-rule:nonzero;display:inline;overflow:visible;visibility:visible;opacity:1;isolation:auto;mix-blend-mode:normal;color-interpolation:sRGB;color-interpolation-filters:linearRGB;solid-color:#000000;solid-opacity:1;vector-effect:none;fill:#b9ffb9;fill-opacity:1;fill-rule:nonzero;stroke:#006400;stroke-width:2.8125;stroke-linecap:round;stroke-linejoin:round;stroke-miterlimit:4;stroke-dasharray:none;stroke-dashoffset:0;stroke-opacity:1;color-rendering:auto;image-rendering:auto;shape-rendering:auto;text-rendering:auto;enable-background:accumulate"
id="rect4424-3-2-9-7-3-3-5-3-1"
@@ -1258,7 +1259,7 @@
x="618.59131"
y="552.08746"
style="font-size:25.00000191px;line-height:1.25;font-family:sans-serif;text-align:center;text-anchor:middle;stroke-width:1px"
- id="tspan1287-9">Slave</tspan></text>
+ id="tspan1287-9">Target</tspan></text>
<path
style="fill:none;fill-rule:evenodd;stroke:#000000;stroke-width:1.99968743;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1;marker-end:url(#DotM)"
d="m 150,583.61221 v 93.75"
diff --git a/Documentation/i2c/summary.rst b/Documentation/i2c/summary.rst
index a1e5c0715f8b..a6da1032fa06 100644
--- a/Documentation/i2c/summary.rst
+++ b/Documentation/i2c/summary.rst
@@ -31,15 +31,16 @@ implement all the common SMBus protocol semantics or messages.
Terminology
===========
-Using the terminology from the official documentation, the I2C bus connects
-one or more *master* chips and one or more *slave* chips.
+The I2C bus connects one or more *controller* chips and one or more *target*
+chips.
+
.. kernel-figure:: i2c_bus.svg
- :alt: Simple I2C bus with one master and 3 slaves
+ :alt: Simple I2C bus with one controller and 3 targets
Simple I2C bus
-A **master** chip is a node that starts communications with slaves. In the
+A **controller** chip is a node that starts communications with targets. In the
Linux kernel implementation it is called an **adapter** or bus. Adapter
drivers are in the ``drivers/i2c/busses/`` subdirectory.
@@ -48,8 +49,8 @@ whole class of I2C adapters. Each specific adapter driver either depends on
an algorithm driver in the ``drivers/i2c/algos/`` subdirectory, or includes
its own implementation.
-A **slave** chip is a node that responds to communications when addressed
-by the master. In Linux it is called a **client**. Client drivers are kept
+A **target** chip is a node that responds to communications when addressed
+by the controller. In Linux it is called a **client**. Client drivers are kept
in a directory specific to the feature they provide, for example
``drivers/media/gpio/`` for GPIO expanders and ``drivers/media/i2c/`` for
video-related chips.
@@ -57,3 +58,13 @@ video-related chips.
For the example configuration in figure, you will need a driver for your
I2C adapter, and drivers for your I2C devices (usually one driver for each
device).
+
+Outdated terminology
+--------------------
+
+In earlier I2C specifications, controller was named "master" and target was
+named "slave". These terms have been obsoleted with v7 of the specification and
+their use is also discouraged by the Linux Kernel Code of Conduct. You may
+still find them in references to documentation which has not been updated. The
+general attitude, however, is to use the inclusive terms: controller and
+target. Work to replace the old terminology in the Linux Kernel is on-going.
--
2.43.0
Because Linux can be a target as well, add terminology to differentiate
between Linux being the target and Linux accessing targets.
Signed-off-by: Wolfram Sang <[email protected]>
---
Documentation/i2c/summary.rst | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/Documentation/i2c/summary.rst b/Documentation/i2c/summary.rst
index a6da1032fa06..ff8bda32b9c3 100644
--- a/Documentation/i2c/summary.rst
+++ b/Documentation/i2c/summary.rst
@@ -49,10 +49,15 @@ whole class of I2C adapters. Each specific adapter driver either depends on
an algorithm driver in the ``drivers/i2c/algos/`` subdirectory, or includes
its own implementation.
-A **target** chip is a node that responds to communications when addressed
-by the controller. In Linux it is called a **client**. Client drivers are kept
-in a directory specific to the feature they provide, for example
-``drivers/media/gpio/`` for GPIO expanders and ``drivers/media/i2c/`` for
+A **target** chip is a node that responds to communications when addressed by a
+controller. In the Linux kernel implementation it is called a **client**. While
+targets are usually separate external chips, Linux can also act as a target
+(needs hardware support) and respond to another controller on the bus. This is
+then called a **local target**. In contrast, an external chip is called a
+**remote target**.
+
+Target drivers are kept in a directory specific to the feature they provide,
+for example ``drivers/gpio/`` for GPIO expanders and ``drivers/media/i2c/`` for
video-related chips.
For the example configuration in figure, you will need a driver for your
--
2.43.0
This not only includes rewording, but also where to put which emphasis
on terms in this document.
Signed-off-by: Wolfram Sang <[email protected]>
---
Documentation/i2c/summary.rst | 33 ++++++++++++++++++++-------------
1 file changed, 20 insertions(+), 13 deletions(-)
diff --git a/Documentation/i2c/summary.rst b/Documentation/i2c/summary.rst
index ff8bda32b9c3..90f46f1504fe 100644
--- a/Documentation/i2c/summary.rst
+++ b/Documentation/i2c/summary.rst
@@ -31,9 +31,7 @@ implement all the common SMBus protocol semantics or messages.
Terminology
===========
-The I2C bus connects one or more *controller* chips and one or more *target*
-chips.
-
+The I2C bus connects one or more controller chips and one or more target chips.
.. kernel-figure:: i2c_bus.svg
:alt: Simple I2C bus with one controller and 3 targets
@@ -41,16 +39,16 @@ chips.
Simple I2C bus
A **controller** chip is a node that starts communications with targets. In the
-Linux kernel implementation it is called an **adapter** or bus. Adapter
-drivers are in the ``drivers/i2c/busses/`` subdirectory.
+Linux kernel implementation it is called an "adapter" or "bus". Controller
+drivers are usually in the ``drivers/i2c/busses/`` subdirectory.
-An **algorithm** contains general code that can be used to implement a
-whole class of I2C adapters. Each specific adapter driver either depends on
-an algorithm driver in the ``drivers/i2c/algos/`` subdirectory, or includes
-its own implementation.
+An **algorithm** contains general code that can be used to implement a whole
+class of I2C controllers. Each specific controller driver either depends on an
+algorithm driver in the ``drivers/i2c/algos/`` subdirectory, or includes its
+own implementation.
A **target** chip is a node that responds to communications when addressed by a
-controller. In the Linux kernel implementation it is called a **client**. While
+controller. In the Linux kernel implementation it is called a "client". While
targets are usually separate external chips, Linux can also act as a target
(needs hardware support) and respond to another controller on the bus. This is
then called a **local target**. In contrast, an external chip is called a
@@ -60,9 +58,18 @@ Target drivers are kept in a directory specific to the feature they provide,
for example ``drivers/gpio/`` for GPIO expanders and ``drivers/media/i2c/`` for
video-related chips.
-For the example configuration in figure, you will need a driver for your
-I2C adapter, and drivers for your I2C devices (usually one driver for each
-device).
+For the example configuration in the figure above, you will need one driver for
+the I2C controller, and drivers for your I2C targets. Usually one driver for
+each target.
+
+Synonyms
+--------
+
+As mentioned above, the Linux I2C implementation historically uses the terms
+"adapter" for controller and "client" for target. A number of data structures
+have these synonyms in their name. So, to discuss implementation details, it
+might be easier to use these terms. If speaking about I2C in general, the
+official terminology is preferred.
Outdated terminology
--------------------
--
2.43.0
Fastest I2C mode is 5 MHz. Update the docs and reword the paragraph
slightly.
Signed-off-by: Wolfram Sang <[email protected]>
Reviewed-by: Easwar Hariharan <[email protected]>
---
Documentation/i2c/summary.rst | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/Documentation/i2c/summary.rst b/Documentation/i2c/summary.rst
index e3ab1d414014..a1e5c0715f8b 100644
--- a/Documentation/i2c/summary.rst
+++ b/Documentation/i2c/summary.rst
@@ -3,8 +3,8 @@ Introduction to I2C and SMBus
=============================
I²C (pronounce: I squared C and written I2C in the kernel documentation) is
-a protocol developed by Philips. It is a slow two-wire protocol (variable
-speed, up to 400 kHz), with a high speed extension (3.4 MHz). It provides
+a protocol developed by Philips. It is a two-wire protocol with variable
+speed (typically up to 400 kHz, high speed modes up to 5 MHz). It provides
an inexpensive bus for connecting many types of devices with infrequent or
low bandwidth communications needs. I2C is widely used with embedded
systems. Some systems use variants that don't meet branding requirements,
--
2.43.0
Luckily, the specs are directly downloadable again, so update the link.
Also update its title to the original name "I²C".
Signed-off-by: Wolfram Sang <[email protected]>
Reviewed-by: Easwar Hariharan <[email protected]>
---
Documentation/i2c/summary.rst | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/Documentation/i2c/summary.rst b/Documentation/i2c/summary.rst
index 28ff80a2302b..e3ab1d414014 100644
--- a/Documentation/i2c/summary.rst
+++ b/Documentation/i2c/summary.rst
@@ -11,11 +11,9 @@ systems. Some systems use variants that don't meet branding requirements,
and so are not advertised as being I2C but come under different names,
e.g. TWI (Two Wire Interface), IIC.
-The latest official I2C specification is the `"I2C-bus specification and user
-manual" (UM10204) <https://www.nxp.com/webapp/Download?colCode=UM10204>`_
-published by NXP Semiconductors. However, you need to log-in to the site to
-access the PDF. An older version of the specification (revision 6) is archived
-`here <https://web.archive.org/web/20210813122132/https://www.nxp.com/docs/en/user-guide/UM10204.pdf>`_.
+The latest official I2C specification is the `"I²C-bus specification and user
+manual" (UM10204) <https://www.nxp.com/docs/en/user-guide/UM10204.pdf>`_
+published by NXP Semiconductors, version 7 as of this writing.
SMBus (System Management Bus) is based on the I2C protocol, and is mostly
a subset of I2C protocols and signaling. Many I2C devices will work on an
--
2.43.0
Hi Wolfram,
On Fri, Jun 14, 2024 at 10:12:39AM GMT, Wolfram Sang wrote:
> Change the first paragraphs to contain only one space after the end of
> the previous sentence like in the rest of the document.
>
> Signed-off-by: Wolfram Sang <[email protected]>
> Reviewed-by: Easwar Hariharan <[email protected]>
Reviewed-by: Andi Shyti <[email protected]>
Thanks,
Andi
Hi Wolfram,
On Fri, Jun 14, 2024 at 10:12:40AM GMT, Wolfram Sang wrote:
> Luckily, the specs are directly downloadable again, so update the link.
> Also update its title to the original name "I?C".
>
> Signed-off-by: Wolfram Sang <[email protected]>
> Reviewed-by: Easwar Hariharan <[email protected]>
Reviewed-by: Andi Shyti <[email protected]>
Thanks,
Andi
Hi Wolfram,
On Fri, Jun 14, 2024 at 10:12:41AM GMT, Wolfram Sang wrote:
> Fastest I2C mode is 5 MHz. Update the docs and reword the paragraph
> slightly.
> Signed-off-by: Wolfram Sang <[email protected]>
> Reviewed-by: Easwar Hariharan <[email protected]>
> ---
> Documentation/i2c/summary.rst | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/i2c/summary.rst b/Documentation/i2c/summary.rst
> index e3ab1d414014..a1e5c0715f8b 100644
> --- a/Documentation/i2c/summary.rst
> +++ b/Documentation/i2c/summary.rst
> @@ -3,8 +3,8 @@ Introduction to I2C and SMBus
> =============================
>
> I?C (pronounce: I squared C and written I2C in the kernel documentation) is
> -a protocol developed by Philips. It is a slow two-wire protocol (variable
> -speed, up to 400 kHz), with a high speed extension (3.4 MHz). It provides
> +a protocol developed by Philips. It is a two-wire protocol with variable
> +speed (typically up to 400 kHz, high speed modes up to 5 MHz). It provides
In a single sentence explanation this is correct :-)
Reviewed-by: Andi Shyti <[email protected]>
Thanks,
Andi
> an inexpensive bus for connecting many types of devices with infrequent or
> low bandwidth communications needs. I2C is widely used with embedded
> systems. Some systems use variants that don't meet branding requirements,
> --
> 2.43.0
>
Hi Wolfram,
On Fri, Jun 14, 2024 at 10:12:42AM GMT, Wolfram Sang wrote:
> We now have the updated I2C specs and our own Code of Conduct, so we
> have all we need to switch over to the inclusive terminology. Define
> them here.
>
> Signed-off-by: Wolfram Sang <[email protected]>
Reviewed-by: Andi Shyti <[email protected]>
Thanks,
Andi
Hi Wolfram,
...
> -A **target** chip is a node that responds to communications when addressed
> -by the controller. In Linux it is called a **client**. Client drivers are kept
> -in a directory specific to the feature they provide, for example
> -``drivers/media/gpio/`` for GPIO expanders and ``drivers/media/i2c/`` for
> +A **target** chip is a node that responds to communications when addressed by a
> +controller. In the Linux kernel implementation it is called a **client**. While
I am not a big fan of the use of the word client. It's not used
anywhere in the documentation and it's too generic as a name for
giving it a specific meaning.
I've seen already some confusion amongst reviewers and
maintainers when Easwar sent the patch in drm.
If it depends on me, I would stick to the only controller/target
and render obsolet the use of the word "client" in the i2c
context.
Andi
> +targets are usually separate external chips, Linux can also act as a target
> +(needs hardware support) and respond to another controller on the bus. This is
> +then called a **local target**. In contrast, an external chip is called a
> +**remote target**.
> +
> +Target drivers are kept in a directory specific to the feature they provide,
> +for example ``drivers/gpio/`` for GPIO expanders and ``drivers/media/i2c/`` for
> video-related chips.
>
> For the example configuration in figure, you will need a driver for your
> --
> 2.43.0
>