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Kernel module for handling Atmel crypto chip (ATSHA204)
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README.md

atsha204-i2c

Coverity Scan Build Status [![Stories in Ready](https://badge.waffle.io/cryptotronix/atsha204-i2c.png?label=ready&title=Ready)](https://waffle.io/cryptotronix/atsha204-i2c)

Kernel module for Atmel's ATSHA204 I2C device.

This software is in ALPHA. It is subject to drastic refactoring at will by the author.

This module provides the following features:

  • An I2C driver [working]
  • Sysfs for serial number [working]
  • Char device for random data [working]

SYSFS

The systfs looks like this:

|-- configlocked
|-- configzone
|-- datalocked
|-- driver -> ../../../../../bus/i2c/drivers/atsha204-i2c
|-- misc
|   `-- atsha0
|       |-- dev
|       |-- device -> ../../../1-0060
|       |-- power
|       |   |-- autosuspend_delay_ms
|       |   |-- control
|       |   |-- runtime_active_time
|       |   |-- runtime_status
|       |   `-- runtime_suspended_time
|       |-- subsystem -> ../../../../../../../class/misc
|       `-- uevent
|-- modalias
|-- name
|-- power
|   |-- autosuspend_delay_ms
|   |-- control
|   |-- runtime_active_time
|   |-- runtime_status
|   `-- runtime_suspended_time
|-- serialnum
|-- subsystem -> ../../../../../bus/i2c
`-- uevent

The unique features are: configlocked, configzone, datalocked, and serialnum.

configlocked & datalocked return a 1 or 0 where 1 indicates that zone is "locked".

serial number returns the chip's unique serial number.

configzone dumps the chip's entire configuration zone.

RANDOM

This driver plugs into /dev/hwrng. See the /dev/hwrng documentation for how to use / switch random number generators.

/dev/atshaX

The driver handles the communication layer. It expects commands in the format:

[Opcode (1)][Param1 (1)][Param2 (2)][[Data (x)]]

The number indicate the number of bytes. Data is optional. The data must be written to the fd in one shot. The driver will pre-pend the length and append the crc.

The driver will perform a write AND a read as there are specific timing constraints when the data must be read. The read data is cached until the user reads the data. The user receives the message ONLY, the single byte size and crc are removed.

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