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i2c_shell: restore documentation on scan technique

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When this code was moved from a standalone sample to an optional shell
feature the documentation on how this works and caveats was lost.  Put
it back so it can be referenced in issue explanations.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
This commit is contained in:
Peter Bigot 2020-09-02 08:09:23 -05:00 committed by Anas Nashif
parent e997c46e6d
commit d3e8d6c3f3
1 changed files with 13 additions and 0 deletions
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13
drivers/i2c/i2c_shell.c
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@ -19,6 +19,19 @@ LOG_MODULE_REGISTER(i2c_shell, CONFIG_LOG_DEFAULT_LEVEL);
/* Maximum bytes we can write or read at once */
#define MAX_I2C_BYTES 16
/*
* This sends I2C messages without any data (i.e. stop condition after
* sending just the address). If there is an ACK for the address, it
* is assumed there is a device present.
*
* WARNING: As there is no standard I2C detection command, this code
* uses arbitrary SMBus commands (namely SMBus quick write and SMBus
* receive byte) to probe for devices. This operation can confuse
* your I2C bus, cause data loss, and is known to corrupt the Atmel
* AT24RF08 EEPROM found on many IBM Thinkpad laptops.
*
* https://manpages.debian.org/buster/i2c-tools/i2cdetect.8.en.html
*/
static int cmd_i2c_scan(const struct shell *shell,
size_t argc, char **argv)
{