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3b56ff4820
The i2cdetect uses the SMBus Quick command by default to scan devices
on the I2C bus. The FT260 implements an I2C bus controller. The SMBus
is derived from I2C, but there are several differences between the
specifications of the two buses in the areas of timing, protocols,
operation modes, and electrical characteristics.
One of the differences is that the I2C devices allow the slave not
to ACK its slave address, but SMBus requires it to always ACK it as
a mechanism to detect a detachable device’s presence on the bus.
Since FT260 is the I2C bus controller, it does not acknowledge the
SMBus Quick write command, which sends a single bit to the device at
the place of the RD/WR bit.
The ft260 driver attempted to mimic the SMBus Quick Write functionality
by writing a single byte as the SMBus Byte Write command does.
Usually, one byte in the SMBus Quick Write will be fine. However, it may
cause problems with devices with a control register at offset 0, like
i2c muxes, for example, when scanned with the i2cdetect utility.
The i2cdetect with the "-r" option uses the SMBus Read Byte command,
which is a reasonable workaround. To prevent the I2C bus from locking
at write-only devices (most notably clock chips at address 0x69), use
the "-r" option in conjunction with scanning range parameters.
This patch removes the SMBus Quick command support.
$ sudo i2cdetect -y 13
Warning: Can't use SMBus Quick Write command, will skip some addresses
0 1 2 3 4 5 6 7 8 9 a b c d e f
00:
10:
20:
30: -- -- -- -- -- -- -- --
40:
50: 50 51 -- -- -- -- -- -- -- -- -- -- -- -- -- --
60:
70:
$ sudo i2cdetect -y -r 13
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: 50 51 -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
Reported-by: Vince Asbridge <VAsbridge@sanblaze.com>
Reported-by: Stephen Shirron <SShirron@sanblaze.com>
Reported-by: Enrik Berkhan <Enrik.Berkhan@inka.de>
Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
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| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.