[PATCH V4 03/12] drivers: Add boot constraints core

Greg Kroah-Hartman
2017-12-13T09:42:27Z

On Sun, Oct 29, 2017 at 07:18:51PM +0530, Viresh Kumar wrote:
> Some devices are powered ON by the bootloader before the bootloader
> handovers control to Linux. It maybe important for those devices to keep
> working until the time a Linux device driver probes the device and
> reconfigure its resources.
>
> A typical example of that can be the LCD controller, which is used by
> the bootloaders to show image(s) while the platform is booting into
> Linux. The LCD controller can be using some resources, like clk,
> regulators, PM domain, etc, that are shared between several devices.
> These shared resources should be configured to satisfy need of all the
> users. If another device's (X) driver gets probed before the LCD
> controller driver in this case, then it may end up reconfiguring these
> resources to ranges satisfying the current users (only device X) and
> that can make the LCD screen unstable.
>
> This patch introduces the concept of boot-constraints, which will be set
> by the bootloaders and the kernel will satisfy them until the time
> driver for such a device is probed (successfully or unsuccessfully).
>
> The list of boot constraint types is empty for now, and will be
> incrementally updated by later patches.
>
> Only two routines are exposed by the boot constraints core for now:

I think we need some documentation somewhere on how to use this, right?

thanks,

greg k-h