greybus-dev December 2025

greybus-dev@lists.linaro.org

1 participants
1 discussions

[RFC PATCH v2 00/12] greybus: introduce CPC as transport layer

by Damien Riégel

Hi, This patchset brings support for Silicon Labs' CPC (Co-Processor Communication) protocol as transport layer for Greybus. This is introduced as a module that sits between Greybus and CPC Host Device Driver implementations, like SDIO or SPI, which are not part of this RFC. If there's no push back with this RFC, the final patchset ready for upstream will include the SDIO driver. The goal of this module is to implement some of the features of Unipro that Greybus relies upon, like reliable transmission. CPC takes care of detecting transmission errors and retransmit frames if necessary. That feature is not part of the RFC to keep it concise, but it's planned for a future patchset. There's also a flow-control feature, to prevent from sending messages to cports that don't have anymore room. In order to implement these features, a 4-byte header is prepended to Greybus messages, making the whole header 12 bytes (Greybus header itself being 8 bytes). This RFC starts by implementing a shim layer that sits between physical bus drivers (like SDIO and SPI) and Greybus, and progressively add more elements to it to make it useful in its own right. +----------------------------------------------------+ | Greybus | +----------------------------------------------------+ /|\ | \|/ +----------------------------------------------------+ | CPC | +----------------------------------------------------+ /|\ /|\ /|\ | | | \|/ \|/ \|/ +----------+ +---------+ +-----------+ | SDIO | | SPI | | Others | +----------+ +---------+ +-----------+ Changes in v2: - v1 included a new protocol for Bluetooth HCI, this has been dropped to focus on CPC itself - likewise, there was an SPI driver, it has been dropped of this RFC for the same reason - v1 introduced CPC in a big commit, this time it's been split in smaller commits to make review manageable Damien Riégel (12): greybus: cpc: add minimal CPC Host Device infrastructure greybus: cpc: introduce CPC cport structure greybus: cpc: use socket buffers instead of gb_message in TX path greybus: cpc: pack cport ID in Greybus header greybus: cpc: switch RX path to socket buffers greybus: cpc: introduce CPC header structure greybus: cpc: account for CPC header size in RX and TX path greybus: cpc: add and validate sequence numbers greybus: cpc: acknowledge all incoming messages greybus: cpc: use holding queue instead of sending out immediately greybus: cpc: honour remote's RX window greybus: cpc: let host device drivers dequeue TX frames MAINTAINERS | 6 + drivers/greybus/Kconfig | 2 + drivers/greybus/Makefile | 2 + drivers/greybus/cpc/Kconfig | 10 ++ drivers/greybus/cpc/Makefile | 6 + drivers/greybus/cpc/cpc.h | 76 +++++++++ drivers/greybus/cpc/cport.c | 107 ++++++++++++ drivers/greybus/cpc/header.c | 146 +++++++++++++++++ drivers/greybus/cpc/header.h | 54 +++++++ drivers/greybus/cpc/host.c | 287 +++++++++++++++++++++++++++++++++ drivers/greybus/cpc/host.h | 58 +++++++ drivers/greybus/cpc/protocol.c | 169 +++++++++++++++++++ 12 files changed, 923 insertions(+) create mode 100644 drivers/greybus/cpc/Kconfig create mode 100644 drivers/greybus/cpc/Makefile create mode 100644 drivers/greybus/cpc/cpc.h create mode 100644 drivers/greybus/cpc/cport.c create mode 100644 drivers/greybus/cpc/header.c create mode 100644 drivers/greybus/cpc/header.h create mode 100644 drivers/greybus/cpc/host.c create mode 100644 drivers/greybus/cpc/host.h create mode 100644 drivers/greybus/cpc/protocol.c -- 2.49.0

2 hours, 28 minutes

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

greybus-dev December 2025