linux-kernel - Re: [External Email] RE: [PATCH v2] serial: sc16is7xx: Extend IRQ check for negative values

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Message-ID: <23799bf9-c61b-f528-e0e5-03a96d232ecc@systec-electronic.com>
Date: Sat, 18 Jan 2025 18:20:16 +0100 (CET)
From: Andre Werner <andre.werner@...tec-electronic.com>
To: Maarten Brock <Maarten.Brock@...ls.nl>
cc: Andre Werner <andre.werner@...tec-electronic.com>, 
    "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>, 
    "jirislaby@...nel.org" <jirislaby@...nel.org>, 
    "hvilleneuve@...onoff.com" <hvilleneuve@...onoff.com>, 
    "andy@...nel.org" <andy@...nel.org>, 
    "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
    "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>, 
    "lech.perczak@...lingroup.com" <lech.perczak@...lingroup.com>
Subject: Re: [External Email] RE: [PATCH v2] serial: sc16is7xx: Extend IRQ
 check for negative values

Dear Maarten,

> > -----Original Message-----
> > Fix the IRQ check to treat the negative values as No IRQ.
>
> It seems to me that this is a real fix and needs a Fixes tag.
> See below.
>
> > Signed-off-by: Andre Werner <andre.werner@...tec-electronic.com>
> > ---
> > diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
> > index 7b51cdc274fd..560f45ed19ae 100644
> > --- a/drivers/tty/serial/sc16is7xx.c
> > +++ b/drivers/tty/serial/sc16is7xx.c
> > @@ -1561,7 +1561,7 @@ int sc16is7xx_probe(struct device *dev, const struct
> > sc16is7xx_devtype *devtype,
> >  	/* Always ask for fixed clock rate from a property. */
> >  	device_property_read_u32(dev, "clock-frequency", &uartclk);
> >
> > -	s->polling = !!irq;
> > +	s->polling = (irq <= 0);
>
> When irq>=0 these two lines above have a different outcome!
> irq==0   =>   !!irq==false   <=>   (irq<=0)==true
> irq==1   =>   !!irq==true   <=>   (irq<=0)==false

Thanks for the advice. I have not seen this all the time I looked at the
code. I accidentally forget to delete the second '!' as I did with the code
tested at the embedded device. Thanks for the advice.

Should I need to submit this patch again with a Fixup prefix or what needs
to be done?

>
> >  	if (s->polling)
> >  		dev_dbg(dev,
> >  			"No interrupt pin definition, falling back to polling mode\n");
>
> Kind regards,
> Maarten
>

Regards,
André