linux-kernel - Re: [PULL -- 5.1 REGRESSION] Bluetooth: btusb: request wake pin with NOAUTOEN

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Message-ID: <CA+ASDXMYiDpYx06LDrZcn5gVWu_7q3DK5G0Eb1jmwjUJZAA_KQ@mail.gmail.com>
Date:   Wed, 10 Apr 2019 10:44:17 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-bluetooth <linux-bluetooth@...r.kernel.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Rajat Jain <rajatja@...gle.com>,
        Heiko Stuebner <heiko@...ech.de>
Subject: Re: [PULL -- 5.1 REGRESSION] Bluetooth: btusb: request wake pin with NOAUTOEN

On Tue, Apr 9, 2019 at 8:43 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> Either it's edge-triggered and you'll get one possibly spurious
> interrupt for an old issue, or it's level-triggered and setting up the
> hw should bring the irq line inactive and you'll be ok.

I think our key difference here is in how much we trust the device:
knowing the quality of the firmware running on some of these devices,
I wouldn't totally trust that they get it right. (It's not fatal if we
allow a buggy firmware to provide an occasional spurious wakeup, but
it's much less OK to allow it a window for flooding us with
interrupts.) So while your suggestion is indeed correct for
well-behaved devices, I think both approaches have value.

> But I've applied your patch for now simply because it seems to be a
> smaller change.

Awesome, thanks!

> But I think you should look into whether it can be fixed by just
> requesting the irq once the hardware is really up (which may indeed be
> as late as open time).

Yes, I will take a look at that for future release cycles. It's a nice
addition regardless, I think.

Brian