Thank you very much Jean and Giampolo.
After reading again the kernel GPIO Documentation, I have some doubts
that I would like to resolve and any word about them would be
apreciated. Please excuse me if the following questions seem too obvious
or are wrong formulated. I am very new to I2C and GPIO and can not get
much more information from the results of my searches.
From Jean's words and the following citation in the GPIO Documentation
523 Board Support
524 -------------
525 For external GPIO controllers -- such as I2C or SPI expanders,
ASICs, multi
526 function devices, FPGAs or CPLDs -- most often board-specific
code handles
527 registering controller devices and ensures that their drivers
know what GPIO
528 numbers to use with gpiochip_add(). Their numbers often start
right after
529 platform-specific GPIOs.
530
531 For example, board setup code could create structures
identifying the range
532 of GPIOs that chip will expose, and passes them to each GPIO
expander chip
533 using platform_data. Then the chip driver's probe() routine
could pass that
534 data to gpiochip_add().
This platform-specific code is what Jean refers to, and must be compiled
into the kernel.
If this is right, do we need to recompile the whole kernel with the new
code for your board, or we can compile only the code for a particular
board and load it as a module? And then, how can we access to the GPIO
pins from a userspace program?
In several pages I have read three different modules are mentioned,
namely pca953x, i2c-dev and i2c-gpio. Could anybody clarify what is the
exact function of each of these modules, please?
Does the pca953x just use the previous platform code and the general
GPIO support kernel facilities to expose the GPIO chip in the user space
under /sys/class/gpio ?
Does the i2c-dev module give an alternative way to access to a generic
i2c device via i2cget? If this is true, how can we access the GPIO pins
from a program in that case?
What does the i2c-gpio module do?
Thanks everyone in advance.
--
To unsubscribe from this list: send the line "unsubscribe linux-i2c" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
