On Tue, 21 Apr 2009 12:00:02 -0400, Jon Smirl wrote: > On Tue, Apr 21, 2009 at 10:11 AM, Michael Lawnick <ml.lawnick@xxxxxx> wrote: > > Jean Delvare said the following: > >> You apparently still have a hard time differentiating between devices > >> and drivers. Loading modules at runtime != instantiating devices at > >> runtime. > >> > > Well, till now I assumed that you can't instantiate a device who's > > driver isn't loaded. But I am eager to learn. > > > >> (And both can be done, but if you can't define your needs, we won't go > >> very far.) > > > > I thought I had explained very often. I'll do it once again: > > We load drivers at runtime directly after boot which does automatic > > instantiation. There will occur further devices on bus after some time > > (hotplug) and therefore we need later on instantiation without reloading > > drivers. We cannot define which devices will exactly be plugged in, it > > might even be possible that on same bus address there occur different > > devices (as an possible option and not at same time of course). So > > device detection is highly appreciated. > > Do you need more info? > > Jean, haven't you told me multiple times that hotplug doesn't work for > i2c? How can you tell when a new device has been added to an i2c bus? I did say so, and I maintain this assertion. Warm-plug, on the other hand, could be supported (but isn't yet.) By warm-plug, I mean: switch off one "channel" of a multiplexer, add one chip to that segment, and enable the channel again. Once we have multiplexing support, this should be doable, if we implement the proper interface. But this really is per-segment, not per-device. Of course this can never be hot-plug like e.g. USB has it: you're not going to get a signal when a new I2C device is connected. This has to be a partly manual process, where you tell the system that a new I2C segment is available, and that the usual rules (per-board instantiation or device detection) have to be applied. > There is already code in the kernel that will dynamically load the > correct i2c device drivers based on the device tree. The i2c drivers > don't need to be build into the kernel. Just put drivers for all of > your devices onto the initrd. -- 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
