On Wed, 29 May 2013, Jean Delvare wrote: > I am worried and confused by some Kconfig dependencies in the HID > subsystem. > > There are 11 HID device drivers which are defined in drivers/hid/Kconfig > with: > > tristate "..." if EXPERT > default !EXPERT > > Unless EXPERT is enabled (and that's not the default), these driver > entries are hidden and automatically selected. If CONFIG_HID=m, they are > selected as modules. If CONFIG_HID=y, they are built into the kernel. So > it is impossible to have CONFIG_HID=y and build these device drivers as > modules - as device drivers typically are. > > I would like to understand the reasoning behind this complexity. What is > so special about these 11 drivers, that we can't just let the (kernel > configuring) user chose if he/she wants them and in what form? That's quite a old story with some history behind. Linus himself originally requested it, then much later asked the same question you did. See some background here: https://lkml.org/lkml/2010/5/20/227 The thing is, that things indeed have changed quite a bit since then. We are no longer in a situation that the generic driver would serve 99.99% of the world and the specific drivers would be just quirks. > Wouldn't "default !EXPERT" and a good old "If unsure, say Y" in the help > text be enough? Normally, yes. This was all introduced back when separating out all the messy quirks from generic hid driver into sub-drivers for maintaing sort-of backwards compatibility and avoid confusion. > Also I find it unpleasant that this construct completely hides the > option from the user, as if it did not exist, except if other options > depend on it. This is inconsistent and makes it difficult for the user > to know whether a specific kernel version includes a given driver or not > (one has to check .config afterward to know the answer.) Yes. Again, purely historical reasons. > Put in short, I don't like the way things are today and would welcome > changes in this area. As things have changed a lot since 2.6.28, we can try to put things more in line now for 3.11 or so. -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
