add support for 8-bit and I2C variants of the chip:
- MCP23008 / MCP23S08: 8-bit (I2C / SPI)
- MCP23017 / MCP23S17: 16-bit (I2C / SPI)
- MCP23018 / MCP23S18: 16-bit (I2C / SPI), open-drain outputs
The MCP23x17 and MCP23x18 are essentially identical, software-wise; we
merely report different GPIO pin capabilities (no push-pull output for
MCP23x18). Also, remove the tri-state capability that was previously
advertised by the old version of this driver; these chips have no way
to put the pin into a HI-Z mode.
All 3 I2C versions are supported, but the SPI front-end still only
supports the MCP23S17 for now (SPI autoconfiguration needs an overhaul).
mcp23s17gpio(4) remains present as a link to the new mcpgpio(4) man page.
XXX Still to-do: FDT integration, interrupt suppoort.
- Can't run iic_exec in softint because it does cv_wait, at least on
some i2c controllers -- defer to workqueue instead.
- Fix violations of locking rules:
. Do not take a lock at higher IPL than it is defined at!
. Do not sleep under a lock!
. Definitely do not sleep under a spin lock!
In this case, sc_intr_lock was defined at IPL_VM but used at IPL_TTY,
and i2c transactions -- possibly causing sleep for cv_wait -- were
issued under it.
But in this case, the interrupt handler needs only a single bit to
mark whether the work is pending, so just use atomic_swap for that.
- Use an adaptive lock (IPL_NONE) for i2c transactions.
- Detach children, and do so before freeing anything.
Driver module as illustrated here:
https://www.sparkfun.com/products/13911
A SCMD module is a ARM SOC simular to a Arduino in front of a motor
driver chip. The single SCMD module can control two motors and up to
16 additional modules can be chained together using an internal I2C
bus. One can interface with the SCMD using tty uart commands, SPI or
I2C. The driver in this commit adds a kernel driver for the I2C and
SPI interfaces. The command line utility provides a set of
convenience commands that support most of the functions of the SCMD
and is able to use the tty uart mode, SPI user land or the included
kernel driver in a uniform manor.
The use of the SCMD module is mostly for small robots and the like,
but it can control anything that is controllable by voltage.
One must make sure that you release the i2c bus if you acquire.
One must not try to release the i2c bus if you failed to acquire it.
One can't leave too early from the single-shot refresh without
checking the status register as there may have been a reset
and releasing the i2c bus.
heater element. Disable the heater features in the driver when that
condition is detected and let the attachment succeed. Also mention
that the SHT21 is another clone.
sensor such as:
https://www.adafruit.com/product/2857
This is a higher priced sensor with a lot of features, including the
ability to do sub-second periodic updates. The driver supports
everything about the sensor except for the alert pin.
- comma is followed by space
- KNF multi-line comments
- fold long lines
- early returns, fixes a missed iic_release_bus() on error.
- foo == false -> !foo
chip from Adafruit is:
https://www.adafruit.com/product/4829
This is a moderately priced gas sensor that can detect volatile
organic compounds in the air. The driver uses the 3-clause BSD
licensed VOC algorithm provided by Sensirion to turn the raw sensor
metric into a VOC index which can indicate the quality of the air in a
particular indoor environment. All published functions of the chip
are supported and one unpublished feature.
sensor. An example of this chip is:
https://www.adafruit.com/product/4885
This is a lower cost chip that provides higher then usual precision
according to the data sheet. This driver supports all of the published
functions that the chip has.
thorpej