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From: Roderick Colenbrander <roderick@gaikai.com>
To: "Samuel Čavoj" <samuel@cavoj.net>
Cc: Jiri Kosina <jikos@kernel.org>,
	Benjamin Tissoires <benjamin.tissoires@redhat.com>,
	linux-input@vger.kernel.org, Chris Ye <lzye@google.com>,
	Roderick Colenbrander <roderick.colenbrander@sony.com>
Subject: Re: [PATCH 11/13] HID: playstation: add DualSense player LEDs support.
Date: Sat, 26 Dec 2020 15:07:50 -0800	[thread overview]
Message-ID: <CANndSK=8GobuCcVa8yWqQXaFuAL6vra=vd625aBUK6YiqkVS1A@mail.gmail.com> (raw)
In-Reply-To: <20201226192712.ky56nhdbh6n43bp6@fastboi.localdomain>

Hi Samuel,

Thanks for your review!

On Sat, Dec 26, 2020 at 11:27 AM Samuel Čavoj <samuel@cavoj.net> wrote:
>
> Hi,
>
> I noticed that the `value` argument is not at all used in the
> player_led_set_brightness function.
>
> On 18.12.2020 22:23, Roderick Colenbrander wrote:
> > +
> > +static void dualsense_player_led_set_brightness(struct led_classdev *led, enum led_brightness value)
> > +{
> > +     struct hid_device *hdev = to_hid_device(led->dev->parent);
> > +     struct dualsense *ds = hid_get_drvdata(hdev);
> > +     uint8_t player_leds_state = 0;
> > +     unsigned long flags;
> > +     int i;
> > +
> > +     for (i = 0; i < ARRAY_SIZE(ds->player_leds); i++)
> > +             player_leds_state |= (ds->player_leds[i].brightness << i);
>
> Is it guaranteed at this point, that the led->brightness is set to the
> new value? I'm unfamiliar with the led subsystem, but skimming other
> drivers I found that they update the device based on the value of the
> `value` argument.

See comments below. Normally yes the brightness is already updated,
but as mentioned below it might still be best to change the code.

>
> > +
> > +     spin_lock_irqsave(&ds->base.lock, flags);
> > +     ds->player_leds_state = player_leds_state;
> > +     ds->update_player_leds = true;
> > +     spin_unlock_irqrestore(&ds->base.lock, flags);
> > +
> > +     schedule_work(&ds->output_worker);
> > +}
>
> Reading led-core.c, I found that led_set_brightness_{nosleep,sync} do
> set the brightness attribute, but the _nopm one does not and it is
> exported, although it is not used anywhere other than led-core.c and
> led-class.c.
>
> However, I find the usage in led_classdev_suspend and _resume
> interesting. In suspend, set_brightness_nopm is called with a value of
> 0, which should turn off the LED while retaining the value of the
> brightness attribute, which is later recalled in _resume. I assume the
> intended behaviour is the LED to turn off when suspending and return to
> its original state on resume, without overwriting the attribute.
>
> Assuming that, the "value" argument passed to dualsense_player_led_set_brightness
> can be different from led->brightness *on purpose* and should be used
> instead.
>
> I would write something along these lines:
>
> for (i = 0; i < ARRAY_SIZE(ds->player_leds); i++) {
>         if (&ds->player_leds[i] == led) {
>                 if (value == LED_OFF)
>                         player_leds_state &= ~(1 << i);
>                 else
>                         player_leds_state |= (1 << i);
>                 break;
>         }
> }
>
> This is just me hypothesizing though, could anyone clear this up for
> me? Thank you very much.

Thanks for your deep analysis. While writing the code I already found
it strange there were 2 layers of bookkeeping. As you point out this
is likely due to the power management logic.

The LEDs are created by 'ps_led_register' and it is setting:
    led->flags = LED_CORE_SUSPENDRESUME;

So those code paths would indeed be triggered provided
'CONFIG_PM_SLEEP' is set. So it is probably safest for me to change
that for-loop anyway. I had hoped to skip the 'find the LED logic' (it
just feels ugly somehow, but not a big deal). Let me make this quick
change. I will just wait a few more days on potential other feedback
from the list before submitting a 'v2'. So far nothing major, but just
these few small things :)


>
> Regards,
> Samuel

Thanks,
Roderick


-- 
Roderick Colenbrander
Senior Manager of Hardware & Systems Engineering
Sony Interactive Entertainment LLC
roderick.colenbrander@sony.com

  reply	other threads:[~2020-12-26 23:08 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-19  6:23 [PATCH 00/13] HID: new driver for PS5 'DualSense' controller Roderick Colenbrander
2020-12-19  6:23 ` [PATCH 01/13] HID: playstation: initial DualSense USB support Roderick Colenbrander
2020-12-27 16:23   ` Barnabás Pőcze
2020-12-27 23:04     ` Roderick Colenbrander
2020-12-29 19:12       ` Barnabás Pőcze
2020-12-31  0:08   ` Barnabás Pőcze
2020-12-31  1:08     ` Roderick Colenbrander
2020-12-19  6:23 ` [PATCH 02/13] HID: playstation: use DualSense MAC address as unique identifier Roderick Colenbrander
2020-12-19  6:23 ` [PATCH 03/13] HID: playstation: add DualSense battery support Roderick Colenbrander
2020-12-19  6:23 ` [PATCH 04/13] HID: playstation: add DualSense touchpad support Roderick Colenbrander
2020-12-26  2:14   ` Samuel Čavoj
2020-12-26 22:27     ` Roderick Colenbrander
2020-12-29 19:49   ` Barnabás Pőcze
2020-12-29 21:44     ` Roderick Colenbrander
2020-12-19  6:23 ` [PATCH 05/13] HID: playstation: add DualSense accelerometer and gyroscope support Roderick Colenbrander
2020-12-19  6:23 ` [PATCH 06/13] HID: playstation: track devices in list Roderick Colenbrander
2020-12-19  6:23 ` [PATCH 07/13] HID: playstation: add DualSense Bluetooth support Roderick Colenbrander
2020-12-19  6:23 ` [PATCH 08/13] HID: playstation: add DualSense classic rumble support Roderick Colenbrander
2020-12-19  6:23 ` [PATCH 09/13] HID: playstation: add DualSense lightbar support Roderick Colenbrander
2020-12-27 14:41   ` Barnabás Pőcze
2020-12-28 21:26     ` Roderick Colenbrander
2020-12-29 18:59       ` Barnabás Pőcze
2020-12-29 19:54         ` Roderick Colenbrander
2020-12-29 20:22           ` Barnabás Pőcze
2020-12-19  6:23 ` [PATCH 10/13] HID: playstation: add microphone mute support for DualSense Roderick Colenbrander
2020-12-19  6:23 ` [PATCH 11/13] HID: playstation: add DualSense player LEDs support Roderick Colenbrander
2020-12-26 19:27   ` Samuel Čavoj
2020-12-26 23:07     ` Roderick Colenbrander [this message]
2020-12-27 14:27   ` Barnabás Pőcze
2020-12-28 22:02     ` Roderick Colenbrander
2020-12-29 18:49       ` Barnabás Pőcze
2020-12-19  6:23 ` [PATCH 12/13] HID: playstation: DualSense set LEDs to default player id Roderick Colenbrander
2020-12-27  0:08   ` Samuel Čavoj
2020-12-27 23:07     ` Roderick Colenbrander
2020-12-19  6:23 ` [PATCH 13/13] HID: playstation: report DualSense hardware and firmware version Roderick Colenbrander
2020-12-27 17:06   ` Barnabás Pőcze
2020-12-27 22:21     ` Roderick Colenbrander
2020-12-27 22:27       ` Roderick Colenbrander
2020-12-27 22:37         ` Barnabás Pőcze
2020-12-28 22:45           ` Roderick Colenbrander
2020-12-29 15:10             ` Barnabás Pőcze
2020-12-19  8:38 ` [PATCH 00/13] HID: new driver for PS5 'DualSense' controller Bastien Nocera
2020-12-19 22:39   ` Roderick.Colenbrander

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