On Fri, Aug 25, 2017 at 10:50 AM, Stuart Longland <stuartl@xxxxxxxxxxxxxxxxxx> wrote: > [Note: dropping vadimp@xxxxxxxxxxxxx as SMTP server complained about the > DNS server returning NXDOMAIN. Apologies.] > On 25/08/17 18:32, Linus Walleij wrote: >> Gnah! >> Whoever writes a slot-in replacement making the character device >> take precendence wins lots of karma. > > What would such a replacement look like though? Something that looks for /dev/gpiochipN and if it exists open the GPIOs from there and make that take precedence over any /sys/gpio/* poking. > Some sort of system whereby you can read/write single-line commands as > if talking to a GPIO expander over a UART? I don't really understand the question. All GPIO expanders become a gpiochip, and have their own character device in /dev. > Would you access the GPIOs one by one, or would you perhaps map them > into a bitmap (maybe arbitrarily, up to 64-bits wide) and perform masked > operations on the bitmap? The character device supports up to 64bits of simultaneous line switches, but the in-kernel API can only handle 32bits in a single register write. > I'm no fan of the sysfs GPIO interface, but it beats poking around at > registers behind the kernel's back. Have a look at libgpiod and tools/gpio/* in the kernel. Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
