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Zazzman
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Joined: 09 May 2012
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PostPosted: Fri Nov 10, 2017 9:09 pm    Post subject: missing doc on the Gentoo Wiki: found Reply with quote

https://wiki.gentoo.org/wiki/Hardware_detection

see the ??????? for i2c-tools package? the command we're missing is 'i2cdetect'. within that context, the user would probably only need the
Code:
i2cdetect -l
command. It outputs a neat little list of i2c buses, each with a description that should look deeply related to the kernel drivers necessary.

Correct me if I'm wrong, but card0-DP-1 and so on refers to the first DisplayPort (DP) on the first graphics card. and there's plenty more graphics related bit-bus entries to expect.

Note that other uses of the i2cdetect can destroy your hardware, according to the manpage.

So far, it looks like a nice way to probe for the SMBus/etc driver(s) to compile into your kernel, without having to dive deep into lshw, or pull up a desktop for lshw-gtk.
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josephg
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PostPosted: Tue Jan 09, 2018 7:13 pm    Post subject: Re: missing doc on the Gentoo Wiki: found Reply with quote

Code:
i2cdetect -l

outputs nothing.. 8O what does that mean?
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kite14
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PostPosted: Tue Jan 09, 2018 8:21 pm    Post subject: Reply with quote

josephg wrote:
Code:
i2cdetect -l

outputs nothing.. 8O what does that mean?

I guess the proper kernel driver is not loaded.
According to the README file that comes with the source tarball, these tools need the "i2c-dev" kernel driver
Quote:

https://www.kernel.org/doc/Documentation/i2c/dev-interface

«Usually, i2c devices are controlled by a kernel driver. But it is also
possible to access all devices on an adapter from userspace, through
the /dev interface. You need to load module i2c-dev for this.

Each registered i2c adapter gets a number, counting from 0. You can
examine /sys/class/i2c-dev/ to see what number corresponds to which adapter.
Alternatively, you can run "i2cdetect -l" to obtain a formatted list of all
i2c adapters present on your system at a given time. i2cdetect is part of
the i2c-tools package.»


To build i2c-dev driver, enable CONFIG_I2C_CHARDEV in kernel config (either "Y" or "M")
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kite14
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PostPosted: Tue Jan 09, 2018 8:43 pm    Post subject: Reply with quote

Zazzman,
I edited the wiki page, replacing the "???????" with the appropriate command.
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josephg
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PostPosted: Tue Jan 09, 2018 8:49 pm    Post subject: Reply with quote

kite14 wrote:
I guess the proper kernel driver is not loaded.
According to the README file that comes with the source tarball, these tools need the "i2c-dev" kernel driver

yes thank you. i2c-dev was not loaded. so i modprobe'd it along with all other i2c modules i found. now i have
Code:
$ lsmod | grep i2c
intel_quark_i2c_gpio    12288  0
i2c_slave_eeprom       12288  0
i2c_scmi               12288  0
i2c_ocores             12288  0
i2c_mux_reg            12288  0
i2c_mux_pinctrl        12288  0
i2c_mux_gpio           12288  0
i2c_mux                12288  3 i2c_mux_reg,i2c_mux_pinctrl,i2c_mux_gpio
i2c_ismt               12288  0
i2c_isch               12288  0
i2c_gpio               12288  0
i2c_dev                12288  0
i2c_algo_bit           12288  2 i2c_gpio,i915
i2c_i801               24576  0
i2c_smbus              12288  1 i2c_i801
mfd_core               12288  2 lpc_ich,intel_quark_i2c_gpio


Code:
# i2cdetect -l
i2c-3   i2c             i915 gmbus panel                        I2C adapter
i2c-1   i2c             i915 gmbus ssc                          I2C adapter
i2c-6   i2c             i915 gmbus dpd                          I2C adapter
i2c-4   i2c             i915 gmbus dpc                          I2C adapter
i2c-2   i2c             i915 gmbus vga                          I2C adapter
i2c-0   smbus           SMBus I801 adapter at 5000              SMBus adapter
i2c-7   i2c             DPDDC-D                                 I2C adapter
i2c-5   i2c             i915 gmbus dpb                          I2C adapter


if i sort it, it looks even better
Code:
# i2cdetect -l | sort
i2c-0   smbus           SMBus I801 adapter at 5000              SMBus adapter
i2c-1   i2c             i915 gmbus ssc                          I2C adapter
i2c-2   i2c             i915 gmbus vga                          I2C adapter
i2c-3   i2c             i915 gmbus panel                        I2C adapter
i2c-4   i2c             i915 gmbus dpc                          I2C adapter
i2c-5   i2c             i915 gmbus dpb                          I2C adapter
i2c-6   i2c             i915 gmbus dpd                          I2C adapter
i2c-7   i2c             DPDDC-D                                 I2C adapter


Zazzman wrote:
It outputs a neat little list of i2c buses, each with a description that should look deeply related to the kernel drivers necessary.

how would i relate this to my kernel config? i can only find an i2c_smbus in my kernel config.
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