Hi Lars, On Fri, 6 May 2011 04:30:33 -0700 (PDT), Lars Michael wrote: > On our custom board we have an I2C GPIO port expander. This is used for different things like power supply control and button control. Hence I wrote two modules; pscontrol and button. > > In the modules I use i2c_new_device to create the device and to get the i2c_client struct that I later use in the smbus calls. This works fine, one module at the time. Together the last insmod fails, because the device at that address is already created. > > But how do I access the same I2C device from several modules? Ideally I want to specify the adapter and slave address. If a client is found, I get the i2c_client otherwise I have to create it by i2c_new_device (or probe it). Is it possible? > > Since I know the I2C bus and slave addresses in advance, would it be better to predeclare them by i2c_register_board_info? And in that case, how do I get the i2c_client struct in the module? In general I would have pointed you to drivers/mfd and told you to write a mfd core driver for your chip. However in your case I don't think you have a multifunction device. You have a single function device (GPIO) with multiple users. So I suggest that you simply write a proper gpio driver for your chip, and get the device registered as an I2C GPIO device. Then, in your function drivers (power supply control and button control) get a reference to the gpio device in question, and use it. FWIW, we already have support for many I2C-based GPIO chip families. Take a look in drivers/gpio, files adp5588-gpio.c, max7300.c, max732x.c, pca953x.c, pcf857x.c and sx150x.c. With some luck, your chip is already supported, so all you have to do is instantiate it in your platform code. -- Jean Delvare -- 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
