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Message-ID: <20161223134732.GC12369@marvin.atrad.com.au>
Date: Sat, 24 Dec 2016 00:17:32 +1030
From: Jonathan Woithe <jwoithe@...t42.net>
To: Micha?? K??pie?? <kernel@...pniu.pl>
Cc: Darren Hart <dvhart@...radead.org>,
platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] platform/x86: fujitsu-laptop: use
brightness_set_blocking for LED-setting callbacks
On Fri, Dec 23, 2016 at 10:00:08AM +0100, Micha?? K??pie?? wrote:
> 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: Micha?? K??pie?? <kernel@...pniu.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.
Great catch. Yes, we've known about this limitation for a while, and the
inability to use the LEDs with high rate triggers was also noted earlier
this year. This patch is a welcome development to address that particular
issue.
> 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.
No problem. I am planning to do a coding style cleanup in the near-ish term
future. Having a consistent style across the whole file when the time comes
will make this easier. That is, the above approach is fine in the
circumstances.
> - 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.
I would welcome such a patch if you wish to submit it. My fujitsu hardware
does not have a logo lamp so I am not in a position to develop or test such
a change, but I agree that it is something we should address.
Since my Fujitsu hardware also lacks LEDs I can't runtime test this patch.
However, the rationale makes sense and the patch looks sound.
Acked-by: Jonathan Woithe <jwoithe@...t42.net>
Thanks for your contribution.
Regards
jonathan
> 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
>
> --
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