[PATCH] platform/x86: fujitsu-laptop: use brightness_set_blocking for LED-setting callbacks

["Michał Kępień" <kernel@kempniu.pl>]

All LED-setting functions in fujitsu-laptop are currently assigned to
the brightness_set callback, which is incorrect because they can sleep
(due to their use of call_fext_func(), which in turn issues ACPI calls)
and the documentation (in include/linux/leds.h) clearly states they must
not.  Assign them to brightness_set_blocking instead and change them to
match the expected function prototype.

This change makes it possible to use Fujitsu-specific LEDs with "heavy"
triggers, like disk-activity or phy0rx.

Fixes: 3a407086090b ("fujitsu-laptop: Add BL power, LED control and radio state information")
Fixes: 4f62568c1fcf ("fujitsu-laptop: Support radio LED")
Fixes: d6b88f64b0d4 ("fujitsu-laptop: Add support for eco LED")
Signed-off-by: Michał Kępień <kernel@kempniu.pl>
---
Even back in 2.6.29, when the first Fujitsu-specific LED was introduced,
the brightness_set callback was annotated with the following text: "Must
not sleep, use a workqueue if needed".  To make things easier for LED
drivers, the LED core introduced (in 3.19) brightness_set_sync, which
was later renamed to brightness_set_blocking (in 4.5).  It allows easy
use of brightness-setting callbacks that may sleep, which is exactly
what we need here.

Without this patch, here is a quick way to lock your system up within
seconds:

    # echo disk-activity > "/sys/class/leds/fujitsu::radio_led/trigger"
    # dd if=/dev/sda of=/dev/null bs=1M count=10000

Applying this patch allowed me to successfully perform the above stress
test without a visible influence on system stability on a Lifebook E744
with an SSD.

Two notes about the patch itself:

  - As fujitsu-laptop is already at odds with checkpatch rules, I
    decided to stick with its current coding style so that the
    functional changes introduced by this patch do not blend with
    changes related to coding style.

  - In logolamp_set(), returning the result of the second
    call_fext_func() call as the function return value is obviously
    pretty arbitrary, but nobody has cared about these return values at
    all since day one, so I decided to keep this patch simple.  I can
    submit another one which properly handles call_fext_func() failures
    in that function, if you think that would be helpful.

 drivers/platform/x86/fujitsu-laptop.c | 42 +++++++++++++++++------------------
 1 file changed, 21 insertions(+), 21 deletions(-)

diff --git a/drivers/platform/x86/fujitsu-laptop.c b/drivers/platform/x86/fujitsu-laptop.c
index 61f39abf5dc8..82d67715ce76 100644
--- a/drivers/platform/x86/fujitsu-laptop.c
+++ b/drivers/platform/x86/fujitsu-laptop.c
@@ -177,43 +177,43 @@ static void acpi_fujitsu_hotkey_notify(struct acpi_device *device, u32 event);
 
 #if IS_ENABLED(CONFIG_LEDS_CLASS)
 static enum led_brightness logolamp_get(struct led_classdev *cdev);
-static void logolamp_set(struct led_classdev *cdev,
+static int logolamp_set(struct led_classdev *cdev,
 			       enum led_brightness brightness);
 
 static struct led_classdev logolamp_led = {
  .name = "fujitsu::logolamp",
  .brightness_get = logolamp_get,
- .brightness_set = logolamp_set
+ .brightness_set_blocking = logolamp_set
 };
 
 static enum led_brightness kblamps_get(struct led_classdev *cdev);
-static void kblamps_set(struct led_classdev *cdev,
+static int kblamps_set(struct led_classdev *cdev,
 			       enum led_brightness brightness);
 
 static struct led_classdev kblamps_led = {
  .name = "fujitsu::kblamps",
  .brightness_get = kblamps_get,
- .brightness_set = kblamps_set
+ .brightness_set_blocking = kblamps_set
 };
 
 static enum led_brightness radio_led_get(struct led_classdev *cdev);
-static void radio_led_set(struct led_classdev *cdev,
+static int radio_led_set(struct led_classdev *cdev,
 			       enum led_brightness brightness);
 
 static struct led_classdev radio_led = {
  .name = "fujitsu::radio_led",
  .brightness_get = radio_led_get,
- .brightness_set = radio_led_set
+ .brightness_set_blocking = radio_led_set
 };
 
 static enum led_brightness eco_led_get(struct led_classdev *cdev);
-static void eco_led_set(struct led_classdev *cdev,
+static int eco_led_set(struct led_classdev *cdev,
 			       enum led_brightness brightness);
 
 static struct led_classdev eco_led = {
  .name = "fujitsu::eco_led",
  .brightness_get = eco_led_get,
- .brightness_set = eco_led_set
+ .brightness_set_blocking = eco_led_set
 };
 #endif
 
@@ -267,48 +267,48 @@ static int call_fext_func(int cmd, int arg0, int arg1, int arg2)
 #if IS_ENABLED(CONFIG_LEDS_CLASS)
 /* LED class callbacks */
 
-static void logolamp_set(struct led_classdev *cdev,
+static int logolamp_set(struct led_classdev *cdev,
 			       enum led_brightness brightness)
 {
 	if (brightness >= LED_FULL) {
 		call_fext_func(FUNC_LEDS, 0x1, LOGOLAMP_POWERON, FUNC_LED_ON);
-		call_fext_func(FUNC_LEDS, 0x1, LOGOLAMP_ALWAYS, FUNC_LED_ON);
+		return call_fext_func(FUNC_LEDS, 0x1, LOGOLAMP_ALWAYS, FUNC_LED_ON);
 	} else if (brightness >= LED_HALF) {
 		call_fext_func(FUNC_LEDS, 0x1, LOGOLAMP_POWERON, FUNC_LED_ON);
-		call_fext_func(FUNC_LEDS, 0x1, LOGOLAMP_ALWAYS, FUNC_LED_OFF);
+		return call_fext_func(FUNC_LEDS, 0x1, LOGOLAMP_ALWAYS, FUNC_LED_OFF);
 	} else {
-		call_fext_func(FUNC_LEDS, 0x1, LOGOLAMP_POWERON, FUNC_LED_OFF);
+		return call_fext_func(FUNC_LEDS, 0x1, LOGOLAMP_POWERON, FUNC_LED_OFF);
 	}
 }
 
-static void kblamps_set(struct led_classdev *cdev,
+static int kblamps_set(struct led_classdev *cdev,
 			       enum led_brightness brightness)
 {
 	if (brightness >= LED_FULL)
-		call_fext_func(FUNC_LEDS, 0x1, KEYBOARD_LAMPS, FUNC_LED_ON);
+		return call_fext_func(FUNC_LEDS, 0x1, KEYBOARD_LAMPS, FUNC_LED_ON);
 	else
-		call_fext_func(FUNC_LEDS, 0x1, KEYBOARD_LAMPS, FUNC_LED_OFF);
+		return call_fext_func(FUNC_LEDS, 0x1, KEYBOARD_LAMPS, FUNC_LED_OFF);
 }
 
-static void radio_led_set(struct led_classdev *cdev,
+static int radio_led_set(struct led_classdev *cdev,
 				enum led_brightness brightness)
 {
 	if (brightness >= LED_FULL)
-		call_fext_func(FUNC_RFKILL, 0x5, RADIO_LED_ON, RADIO_LED_ON);
+		return call_fext_func(FUNC_RFKILL, 0x5, RADIO_LED_ON, RADIO_LED_ON);
 	else
-		call_fext_func(FUNC_RFKILL, 0x5, RADIO_LED_ON, 0x0);
+		return call_fext_func(FUNC_RFKILL, 0x5, RADIO_LED_ON, 0x0);
 }
 
-static void eco_led_set(struct led_classdev *cdev,
+static int eco_led_set(struct led_classdev *cdev,
 				enum led_brightness brightness)
 {
 	int curr;
 
 	curr = call_fext_func(FUNC_LEDS, 0x2, ECO_LED, 0x0);
 	if (brightness >= LED_FULL)
-		call_fext_func(FUNC_LEDS, 0x1, ECO_LED, curr | ECO_LED_ON);
+		return call_fext_func(FUNC_LEDS, 0x1, ECO_LED, curr | ECO_LED_ON);
 	else
-		call_fext_func(FUNC_LEDS, 0x1, ECO_LED, curr & ~ECO_LED_ON);
+		return call_fext_func(FUNC_LEDS, 0x1, ECO_LED, curr & ~ECO_LED_ON);
 }
 
 static enum led_brightness logolamp_get(struct led_classdev *cdev)
-- 
2.11.0