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.. SPDX-License-Identifier: GPL-2.0
====================================
Linux kernel JTAG support
====================================
Introduction to JTAG
====================
JTAG is an industry standard for verifying hardware. JTAG provides access to
many logic signals of a complex integrated circuit, including the device pins.
A JTAG interface is a special interface added to a chip.
Depending on the version of JTAG, two, four, or five pins are added.
The connector pins are:
* TDI (Test Data In)
* TDO (Test Data Out)
* TCK (Test Clock)
* TMS (Test Mode Select)
* TRST (Test Reset) optional
JTAG interface is designed to have two parts - basic core driver and
hardware specific driver. The basic driver introduces a general interface
which is not dependent of specific hardware. It provides communication
between user space and hardware specific driver.
Each JTAG device is represented as a char device from (jtag0, jtag1, ...).
Access to a JTAG device is performed through IOCTL calls.
Call flow example:
::
User: open -> /dev/jatgX -> JTAG core driver -> JTAG hardware specific driver
User: ioctl -> /dev/jtagX -> JTAG core driver -> JTAG hardware specific driver
User: close -> /dev/jatgX -> JTAG core driver -> JTAG hardware specific driver
THANKS TO
---------
Contributors to Linux-JTAG discussions include (in alphabetical order,
by last name):
- Ernesto Corona
- Steven Filary
- Vadim Pasternak
- Jiri Pirko
- Oleksandr Shamray
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