linux-kernel - Re: [PATCH v6 4/5] tty: serial: handle HAS

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Message-ID: <64505dc349caa6304506e271293095366ecb6d95.camel@linux.ibm.com>
Date: Tue, 08 Oct 2024 10:56:03 +0200
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: "Maciej W. Rozycki" <macro@...am.me.uk>
Cc: Brian Cain <bcain@...cinc.com>, Marcel Holtmann <marcel@...tmann.org>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        Patrik Jakobsson
 <patrik.r.jakobsson@...il.com>,
        Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Dave Airlie <airlied@...hat.com>, Gerd
 Hoffmann <kraxel@...hat.com>,
        Lucas De Marchi <lucas.demarchi@...el.com>,
        Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, Arnd
 Bergmann <arnd@...db.de>,
        Heiko Carstens <hca@...ux.ibm.com>, linux-kernel@...r.kernel.org,
        linux-hexagon@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, virtualization@...ts.linux.dev,
        spice-devel@...ts.freedesktop.org, intel-xe@...ts.freedesktop.org,
        linux-serial@...r.kernel.org, linux-arch@...r.kernel.org,
        Arnd Bergmann <arnd@...nel.org>
Subject: Re: [PATCH v6 4/5] tty: serial: handle HAS_IOPORT dependencies

On Tue, 2024-10-08 at 10:16 +0200, Niklas Schnelle wrote:
> On Mon, 2024-10-07 at 22:09 +0100, Maciej W. Rozycki wrote:
> > On Mon, 7 Oct 2024, Niklas Schnelle wrote:
> > 
> > > diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
> > > index 6709b6a5f3011db38acc58dc7223158fe4fcf72e..6a638feb44e443a1998980dd037748f227ec1bc8 100644
> > > --- a/drivers/tty/serial/8250/8250_pci.c
> > > +++ b/drivers/tty/serial/8250/8250_pci.c
> > [...]
> > >  	iobase = pci_resource_start(dev, 0);
> > >  	outb(0x0, iobase + CH384_XINT_ENABLE_REG);
> > >  }
> > >  
> > > -
> > >  static int
> > >  pci_sunix_setup(struct serial_private *priv,
> > >  		const struct pciserial_board *board,
> > 
> >  Gratuitous change here.
> > 
> > > diff --git a/drivers/tty/serial/8250/8250_pcilib.c b/drivers/tty/serial/8250/8250_pcilib.c
> > > index ea906d721b2c3eac15c9e8d62cc6fa56c3ef6150..fc1882d7515b5814ff1240ffdbe1009ab908ad6b 100644
> > > --- a/drivers/tty/serial/8250/8250_pcilib.c
> > > +++ b/drivers/tty/serial/8250/8250_pcilib.c
> > > @@ -28,6 +28,10 @@ int serial8250_pci_setup_port(struct pci_dev *dev, struct uart_8250_port *port,
> > >  		port->port.membase = pcim_iomap_table(dev)[bar] + offset;
> > >  		port->port.regshift = regshift;
> > >  	} else {
> > > +		if (!IS_ENABLED(CONFIG_HAS_IOPORT)) {
> > > +			pr_err("Serial port %lx requires I/O port support\n", port->port.iobase);
> > > +			return -EINVAL;
> > > +		}
> > >  		port->port.iotype = UPIO_PORT;
> > >  		port->port.iobase = pci_resource_start(dev, bar) + offset;
> > >  		port->port.mapbase = 0;
> > 
> >  Can we please flatten this conditional and get rid of the negation, and 
> > also use `pci_err' for clear identification (`port->port.iobase' may not 
> > even have been set to anything meaningful if this triggers)?  I.e.:
> > 
> > 		/* ... */
> > 	} else if (IS_ENABLED(CONFIG_HAS_IOPORT)) {
> > 		/* ... */
> > 	} else {
> > 		pci_err(dev, "serial port requires I/O port support\n");
> > 		return -EINVAL;
> > 	}
> > 
> > I'd also say "port I/O" (by analogy to "memory-mapped I/O") rather than 
> > "I/O port", but I can imagine it might be debatable.
> 
> Agree this looks better, will change it.

While changing this I noticed that this isn't aligned with the other
print. There we use dev_warn() and -ENXIO vs -EINVAL. How about we move
serial_8250_need_ioport() to 8250_pcilib.c and use it here too? Then we
also only have a single place for the message.

Thanks,
Niklas