[PATCH] regulator: core: Allow generic coupling only for always-on regulators

[Dmitry Osipenko]

The generic voltage balancer doesn't work correctly if one of regulator
couples turns off. Currently there are no users in kernel for that case,
although let's explicitly show that this case is unsupported for those who
will try to use that feature.

Link: https://lore.kernel.org/linux-samsung-soc/20191008170503.yd6GscYPLxjgrXqDuCO7AJc6i6egNZGJkVWHLlCxvA4@z/
Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
Link: https://lore.kernel.org/r/20191025002240.25288-2-digetx@xxxxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
 drivers/regulator/core.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index a46be221dbdc..a5b2a9b02108 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -4963,6 +4963,12 @@ static int generic_coupler_attach(struct regulator_coupler *coupler,
 		return -EPERM;
 	}
 
+	if (!rdev->constraints->always_on) {
+		rdev_err(rdev,
+			 "Coupling of a non always-on regulator is unimplemented\n");
+		return -ENOTSUPP;
+	}
+
 	return 0;
 }
 
-- 
2.20.1