From mboxrd@z Thu Jan 1 00:00:00 1970 From: gregkh@linuxfoundation.org (Greg Kroah-Hartman) Date: Wed, 13 Dec 2017 10:42:27 +0100 Subject: [PATCH V4 03/12] drivers: Add boot constraints core In-Reply-To: <2868a37e561cab91ba5495a1e14b9548c8e93c3e.1509284255.git.viresh.kumar@linaro.org> References: <2868a37e561cab91ba5495a1e14b9548c8e93c3e.1509284255.git.viresh.kumar@linaro.org> Message-ID: <20171213094227.GC13194@kroah.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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