Hi Lars, On Fri, 13 May 2011 00:47:37 -0700 (PDT), Lars Michael wrote: > --- On Sat, 7/5/11, Jean Delvare <khali@xxxxxxxxxxxx> wrote: > > On Fri, 6 May 2011 04:30:33 -0700 (PDT), Lars Michael > > wrote: > > > 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? > > > > > > > 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. > > Thanks for the advice. I wrote a simple driver for my chip and > instantiated it in the platform code. In order to access the Please submit your driver for integration in the upstream kernel. Others are certainly using the same device! > device from the function modules, I exported an i2c_client get > function, in order to get a reference to the client: > > struct i2c_client *pca950x_get_i2c_client(void) > ..... > EXPORT_SYMBOL(pca950x_get_i2c_client); > > Not sure this is the perfect way to do it, but it works. No, this doesn't seem right. A given system may have more than one PCA950x chip. And symbol dependencies are a hell to handle as soon as things get more complex. Such an export will never be accepted upstream. I can think of 2 ways to handle your problem. 1* Use gpiochip_find(). It is currently only available to drivers if gpiolib is built into the kernel, but I consider this a bug, patch submitted [1] but no reply so far. 2a* Install a bus notifier on i2c bus type, and catch event BUS_NOTIFY_BIND_DRIVER. This only works if you can install the notifier before the pca950x driver binds to the GPIO chip. 2b* Use i2c_for_each_dev() to get a handle to your i2c client. This only works if you are certain that the GPIO chip driver is loaded before the drivers which need it. Option 1* seems much cleaner to me, as it abstracts the bus type completely. After all, sub-drivers should only care about the GPIO functionality and not the technical implementation details. If neither works for you for whatever reason, maybe we can add a helper function to i2c-core to retrieve an i2c_client by bus number and address. Maybe others would find it useful as well. [1] http://marc.info/?l=linux-kernel&m=130293906304999&w=2 -- 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
