On 16/05/18 19:05, Guenter Roeck wrote:

On Wed, May 16, 2018 at 02:51:49PM +0100, Robin Murphy wrote:

quoted

Hi Stefan,

On 16/05/18 14:37, Stefan Wahren wrote:

quoted

Currently there is no easy way to detect under-voltage conditions on a remote
Raspberry Pi. This hwmon driver retrieves the state of the under-voltage sensor
via mailbox interface. The handling based on Noralf's modifications to the
downstream firmware driver. In case of an under-voltage condition only an entry
is written to the kernel log.

CC: "Noralf Tr?nnes" <redacted>
Signed-off-by: Stefan Wahren <redacted>
---
  drivers/hwmon/Kconfig             |  10 ++
  drivers/hwmon/Makefile            |   1 +
  drivers/hwmon/raspberrypi-hwmon.c | 207 ++++++++++++++++++++++++++++++++++++++
  3 files changed, 218 insertions(+)
  create mode 100644 drivers/hwmon/raspberrypi-hwmon.c

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 768aed5..7f935cf 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig

@@ -1298,6 +1298,16 @@ config SENSORS_PWM_FAN
  	  This driver can also be built as a module.  If so, the module
  	  will be called pwm-fan.
+config SENSORS_RASPBERRYPI_HWMON
+	tristate "Raspberry Pi voltage monitor"
+	depends on (ARCH_BCM2835 && RASPBERRYPI_FIRMWARE) || (COMPILE_TEST && !RASPBERRYPI_FIRMWARE)

Since RASPBERRYPI_FIRMWARE already implies ARCH_BCM2835 (via BCM2835_MBOX),
this is just a very roundabout way to say:

	depends on RASPBERRYPI_FIRMWARE || COMPILE_TEST

That would permit SENSORS_RASPBERRYPI_HWMON=y combined with
RASPBERRYPI_FIRMWARE=m, which AFAICS would result in a build error
because include/soc/bcm2835/raspberrypi-firmware.h uses IS_ENABLED()
and not IS_REACHABLE().

But that's only possible when COMPILE_TEST=y, where in any case there 
are stub definitions for the #else case in that header which should 
still be enough to build with, right? (and if not, that's probably its 
own bug)

Nobody's expecting COMPILE_TEST configs to actually boot and work 
perfectly, are they?

Robin.