On Fri, Mar 23, 2018 at 5:34 PM, Stephen Boyd [off-list ref] wrote:

This patchset proposes a solution to describing the valid
pins for a pin controller in a generic way so that qcom
platforms can expose the pins that are really available.

Typically, this has been done by having drivers and firmware
descriptions only use pins they know they have access to, and that
still works now because we no longer read the pin direction at
boot. But there are still some userspace drivers and debugfs facilities
that don't know what pins are available and attempt to read everything
they can. On qcom platforms, this may lead to a system hang, which isn't
very nice behavior, even if root is the only user that can trigger it.

The proposal is to describe the valid pins and then not allow things to
cause problems by using the invalid pins. Obviously, the firmware may
mess this up, so this is mostly a nice to have feature or a safety net
so that things don't blow up easily.

Changes from v3:
 * Split out allocation of mask into subroutine
 * Moved that allocation to kmalloc_array()
 * Updated qcom driver to simplifiy ACPI logic and fix mem leak

As both Timur and Andy are happy with this I applied these five
patches for v4.17 and pushed to the test farm. Let's see what
happens!

Yours,
Linus Walleij