On Tue, 29 Aug 2017, Greg Kroah-Hartman [off-list ref] wrote:

On Tue, Aug 01, 2017 at 02:53:43PM +0530, Viresh Kumar wrote:

quoted

Users must be given an option to discard any constraints set by
bootloaders. For example, consider that a constraint is set for the LCD
controller's supply and the LCD driver isn't loaded by the kernel. If
the user doesn't need to use the LCD device, then he shouldn't be forced
to honour the constraint.

We can also think about finer control of such constraints with help of
some sysfs files, but a kernel parameter is fine to begin with.

Tested-by: Rajendra Nayak <redacted>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 Documentation/admin-guide/kernel-parameters.txt |  3 +++
 drivers/base/boot_constraints/core.c            | 17 +++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index d9c171ce4190..0706d1b6004d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt

@@ -426,6 +426,9 @@
 			embedded devices based on command line input.
 			See Documentation/block/cmdline-partition.txt
 
+	boot_constraints_disable
+			Do not set any boot constraints for devices.

Shouldn't that be the default?  As really, that is what the situation is
today, why force everyone to always enable the disable value?  And
enabling a value to disable something is usually a sign of bad naming...

quoted

+
 	boot_delay=	Milliseconds to delay each printk during boot.
 			Values larger than 10 seconds (10000) are changed to
 			no delay (0).

diff --git a/drivers/base/boot_constraints/core.c b/drivers/base/boot_constraints/core.c
index 366a05d6d9ba..e0c33b2b216f 100644
--- a/drivers/base/boot_constraints/core.c
+++ b/drivers/base/boot_constraints/core.c

@@ -24,6 +24,17 @@
 static LIST_HEAD(constraint_devices);
 static DEFINE_MUTEX(constraint_devices_mutex);
 
+static bool boot_constraints_disabled;

Again, this should only be an "enable" type of option, that kicks in if
you are using this type of bootloader/kernel interaction.  Don't force
someone to disable it.

I might add that "disable" type options lead to annoying double
negatives. Regardless of the default, I'd generally prefer "enable" type
options that you enable/disable as needed.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center