Hello, > I'm facing a small architecture problem on an embedded (MPC8248) design. The > processor has a hardware I2C bus for which a driver exists in the Denx > linuxppc kernel tree at rsync://www.denx.de/git/linux-2.6-denx (the driver is > called i2c-mpc8260, does anyone know if there are plans to integrate it in > mainline kernels ?). No we dont know. > Our hardware platform has a DSL daughterboard on which a PCA9557 GPIO I2C chip > is used to control several DSL functions (resetting chipsets, connecting to > the line, ...). The DSL and PCA9557 chipsets are thus both part of a single > "device", but are not connected to the same bus (the DSL chipset is a > platform device, while the PCA9557 is connected on the I2C bus). Good. > I'm developping the DSL chipset driver, and the needed arises to control the > GPIO lines from inside the driver. I've had a look at some PCI drivers which > need to control I2C devices, and all of them have the I2C chips connected to > an I2C bus controlled by the PCI device. Getting a reference to those chips > is thus quite easy. I'm a bit puzzled regarding how to do the same for my > design. Could anyone advice me on how to get a reference to the PCA9557 from > the DSL platform driver in a clean way ? Well this is a bit problem. There are three ways: 1) create EXPORT_SYMBOL(my_api) with defined API and call it from your PCI device to the PCA driver some RTC drivers did this 2) there is, now obsoleted, method with the i2c command callback. This may be removed in the future. 3) create a class interface for this stuff and register the device in the class I'm taking this aproach to create an watchdog class even for i2c devices... And because perhaps you will not want to have your driver integrated into kernel, and because it is a very special think you may use the #1 method without problems. Please note that if the PCA driver needs to be called from interrupts then you will need some workqueues. See some other RTC drivers for inspiration. (pre 2.6.17 because I think 2.6.17 has already a RTC class) Regards Rudolf
