Re: what is the current/ongoing state of userspace access to GPIO?
Hi, On Wed, May 24, 2017 at 07:58:19AM -0400, Robert P. J. Day wrote: > > ashamed to admit, i haven't been keeping up with this, so AIUI, the > GPIO sysfs interface is deprecated, replaced with character device > files (/dev/gpiochip*) to allow access to GPIO. > > first, i find it curious that this is a move away from sysfs access > to using ioctl(), since i had always thought ioctls were massively > discouraged in new code. is there a document that goes through the > rationale for this change? > > and i notice under Documentation/ABI/ that sysfs-gpio is listed > under "obsolete", while gpio-cdev is listed under "testing". this > seems inconsistent -- how can one be obsolete while the other be > categorized as testing? that just seems strange. > > in any event, is the /dev/gpiochip* interface the recommended > interface now? thanks. Linus Walleij described the rationale in the first commit description. Have a look at 3c702e9987e2. Implementing it with netlink sockets would have made it much more complex, I suppose this is why they chose ioctl? By the way, I can recommend accessing the GPIO chardev with libgpiod: https://github.com/brgl/libgpiod This simplifies using it a lot! The tools are also quite nice. Cheers, Clemens ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: what is the current/ongoing state of userspace access to GPIO?
On Wed, May 24, 2017 at 07:58:19AM -0400, Robert P. J. Day wrote: > in any event, is the /dev/gpiochip* interface the recommended > interface now? Yes. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
what is the current/ongoing state of userspace access to GPIO?
ashamed to admit, i haven't been keeping up with this, so AIUI, the GPIO sysfs interface is deprecated, replaced with character device files (/dev/gpiochip*) to allow access to GPIO. first, i find it curious that this is a move away from sysfs access to using ioctl(), since i had always thought ioctls were massively discouraged in new code. is there a document that goes through the rationale for this change? and i notice under Documentation/ABI/ that sysfs-gpio is listed under "obsolete", while gpio-cdev is listed under "testing". this seems inconsistent -- how can one be obsolete while the other be categorized as testing? that just seems strange. in any event, is the /dev/gpiochip* interface the recommended interface now? thanks. rday -- Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
