From 20738cb9fa7ad74c4f374c5b49c8189277df3a9d Mon Sep 17 00:00:00 2001 From: Wolfram Sang Date: Fri, 21 Jun 2024 09:30:13 +0200 Subject: [PATCH] docs: i2c: summary: be clearer with 'controller/target' and 'adapter/client' pairs This not only includes rewording, but also where to put which emphasis on terms in this document. Signed-off-by: Wolfram Sang Reviewed-by: Easwar Hariharan Signed-off-by: Wolfram Sang --- Documentation/i2c/summary.rst | 41 ++++++++++++++++++++--------------- 1 file changed, 24 insertions(+), 17 deletions(-) diff --git a/Documentation/i2c/summary.rst b/Documentation/i2c/summary.rst index ff8bda32b9c3..579a1c7df200 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 @@ -41,28 +39,37 @@ 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 also 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 -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**. +controller. In the Linux kernel implementation it is also 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 -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, when discussing implementation details, +you should be aware of these terms as well. The official wording is preferred, +though. Outdated terminology --------------------