Hi Rudolf, > > 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 That's not very clean, but would work. > 2) there is, now obsoleted, method with the i2c command callback. This may > be removed in the future. I'd rather not use obsoleted methods. > 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... I'll try that, as it seems to be the cleaner approach. I suppose I'm not the only one who is interested in a GPIO class. > 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. I'll go for #1 first as our deadlines are quite tight, and will try to implement #3 a bit later. Regarding integrating the driver into the mainline kernel, I unfortunately can't do that as the specs are covered by an NDA :-( > 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) Thanks. Laurent Pinchart
