On Tuesday 17 April 2007 12:04 am, Francis Moreau wrote: > BTW, are there any plan to make gpio usable from userspace ? I don't > know if it makes sense but I saw some patches on LKML that did that.
Only the usual plan: someone who wants that feature provides a driver, which can be merged after suitable review. For example, the gpio_keys and leds-gpio drivers already exist to expose some kinds of GPIOs ... though not specifically as GPIOs. And I've seen various drivers that package GPIOs on specific chips, mostly for _exclusive_ use by userspace (no kernel access). In this case I'm not entirely sure how it'd work. I've seen a few drivers which let userspace peek and poke at GPIO signals -- like one for Gumstix boards -- but generalizing the model isn't simple. Sub-problems include: - Configuring the relevant pins. Especially for SOC cases, GPIO roles are multiplexed with several others. So there are two issues: (a) the platform-specific setup of that multiplexing, plus (b) the board-specific knowledge of what pins are truly available for use as GPIOs, and not otherwise in use. - Enumerating those GPIOs to userspace. One SOC might have just a few dozen, another might have a few hundred; and then there are all the board-specific ones, on FPGA or I2C chips etc. - Exposing those pins to userspace. It'd be unsafe to let pins claimed by drivers be managed by userspace; the default should be that only unclaimed GPIOs can be accessed. Those points imply part of a design that includes board-specific hooks of various kinds (maybe delegating a lot to platform code). But nobody's yet provided code that would generalize. - Dave - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
