Hi David, On Sun, 9 Dec 2007 20:39:57 -0800, David Brownell wrote: > From: David Brownell <[EMAIL PROTECTED]> > > Add an empty drivers/gpio directory for gpiolib based GPIO expanders. > We already have three of them (two I2C, one SPI), and there are dozens > of similar chips that only exist for GPIO expansion. > > This won't be the only place to hold such gpio_chip code. Many external > chips add a few GPIOs as secondary functionality, and platform code > frequently needs to closely integrate GPIO and IRQ support. > > This is placed *early* in the build/link sequence since it's common for > other drivers to depend on GPIOs to do their work, so they need to be > initialized early in the device_initcall() sequence.
Note that I foresee potential problems with this. These GPIO drivers need I2C or SPI to be initialized before they can load. However on some systems, I2C or SPI buses are hanging off GPIOs, meaning that these GPIOS need to be initialized before I2C or SPI, respectively. I can imagine weird setups where for example an SPI bus would be driven by an I2C-based GPIO chip, or vice-versa. I sure hope that nobody does this, but you never know... And I'm not sure how we would possibly support this. -- Jean Delvare -- 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/
