50 lines
1.7 KiB
Plaintext
50 lines
1.7 KiB
Plaintext
MODULE: i2c-stub
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DESCRIPTION:
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This module is a very simple fake I2C/SMBus driver. It implements four
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types of SMBus commands: write quick, (r/w) byte, (r/w) byte data, and
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(r/w) word data.
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You need to provide a chip address as a module parameter when loading
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this driver, which will then only react to SMBus commands to this address.
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No hardware is needed nor associated with this module. It will accept write
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quick commands to one address; it will respond to the other commands (also
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to one address) by reading from or writing to an array in memory. It will
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also spam the kernel logs for every command it handles.
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A pointer register with auto-increment is implemented for all byte
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operations. This allows for continuous byte reads like those supported by
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EEPROMs, among others.
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The typical use-case is like this:
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1. load this module
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2. use i2cset (from lm_sensors project) to pre-load some data
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3. load the target sensors chip driver module
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4. observe its behavior in the kernel log
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PARAMETERS:
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int chip_addr:
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The SMBus address to emulate a chip at.
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CAVEATS:
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There are independent arrays for byte/data and word/data commands. Depending
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on if/how a target driver mixes them, you'll need to be careful.
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If your target driver polls some byte or word waiting for it to change, the
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stub could lock it up. Use i2cset to unlock it.
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If the hardware for your driver has banked registers (e.g. Winbond sensors
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chips) this module will not work well - although it could be extended to
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support that pretty easily.
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Only one chip address is supported - although this module could be
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extended to support more.
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If you spam it hard enough, printk can be lossy. This module really wants
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something like relayfs.
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