On Tue, Oct 16, 2012 at 8:51 AM, Lars Poeschel <poesc...@lemonage.de> wrote: > On Monday 15 October 2012 at 15:00:12, Linus Walleij wrote: >> > + /* if io is set to output, just return the saved value */ >> > + if (gpio->gpioa_out & (1 << offset)) >> > + return gpio->gpioa_val & (1 << offset); >> >> That's not going to work if the hardware changes state >> behind the back of the driver right? Oh well, maybe >> it doesn't matter. > > I thought about that and then did this "cache" only in case the gpio is a > output to save to usb ping-pong that is needed otherwise. I thought that > nothing can change to state of the output but the driver itself.
On a second note there is already a standard mechanism for caching registers in the kernel, and that is regmap. Sadly it's a bit undocumented but there are several examples and the code lives in drivers/base/regmap and include/linux/regmap.h Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
