On Mon, Jan 11, 2021 at 12:03:18PM +0200, Tony Lindgren wrote:

Hi,

* Linus Walleij [off-list ref] [210109 21:14]:

quoted

On Sat, Jan 9, 2021 at 3:55 AM Drew Fustini [off-list ref] wrote:

quoted

I discussed my use case and this patch on #armlinux earlier this week
and Alexandre Belloni suggested looking at the pinmux-pins debugfs file.

This sounds reasonable.

quoted

This made me think that a possible solution could be to define a store
function for pinmux-pins to handle something like "<pin#> <function#>".
I believe the ability to activate a pin function (or pin group) from
userspace would satisfy our beagleboard.org use-case.

Does that seem like a reasonable approach?

This sounds like a good approach.

Makes sense to me too.

We may want to make it into a proper sysfs interface eventually to not
require debugfs be enabled in .config. But that's another set of patches,
certainly makes sense to first enable it for debugfs.

Regards,

Tony

I have added a debugfs file "pinmux-set" to pinmux.c. This allows
"<function-number> <group-number>" to be written into that file. The
function pinmux_set_write() calls ops->set_mux() with fsel and gsel.

I'll post an RFC with the code, but I am wondering if it would better
to take the function as a name and then lookup the function number
(fsel)?

thanks,
drew