linux-kernel - Re: [PATCH] USB: serial: cp210x: Fix GPIO in autosuspend

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Message-ID: <20190115102942.GO3691@localhost>
Date:   Tue, 15 Jan 2019 11:29:42 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Karoly Pados <pados@...os.hu>
Cc:     Johan Hovold <johan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: serial: cp210x: Fix GPIO in autosuspend

On Tue, Jan 15, 2019 at 10:26:07AM +0100, Johan Hovold wrote:
> On Tue, Jan 15, 2019 at 09:17:58AM +0000, Karoly Pados wrote:
> > > I think it's better to add the autopm call to gpio210x_gpio_get/set
> > > only. This will allow for a simpler patch, and keeps the autopm handling
> > > confined to the gpio paths.
> > 
> > I'll submit a v2.
> > 
> > >> @@ -1383,6 +1397,7 @@ static void cp210x_gpio_set(struct gpio_chip *gc, unsigned int gpio, int
> > >> value)
> > >> } else {
> > >> u16 wIndex = buf.state << 8 | buf.mask;
> > >> 
> > >> + usb_autopm_get_interface(serial->interface);
> > > 
> > > Also make sure to always check for errors from autopm_get().
> > 
> > I checked everywhere else, the reason I didn't check here is on
> > purpose based on your previous feedback. The caller function here
> > doesn't have a return value, so the only way to return errors is to
> > log, but in my last patch to ftdi_sio you made clear that errors from
> > autopm_get shouldn't get logged. Trying to call usb_control_msg() even
> > though the device could not wake does not cause issues, and the return
> > value from usb_control_msg() clearly identifies the reason for failure
> > (failure due to autosuspend), so error information is not lost either.
> > So I thought not checking here has no real disadvantage and I still
> > stay conformant to your previous guidance.
> 
> Ok, I understand your reasoning, but please do check for errors and bail
> out early if autopm_get() fails. No need to log errors.

Actually, we should probably add the missing error handling to the
callers and have gpio_set() propagate errors too. If you want to take a
stab at that, that could be a follow-on patch.

Thanks,
Johan