linux-kernel - Re: [PATCH v7] serial: support for 16550A serial ports on LP-8x4x

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Message-ID: <1456850782.13244.208.camel@linux.intel.com>
Date:	Tue, 01 Mar 2016 18:46:22 +0200
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Sergei Ianovich <ynvich@...il.com>, linux-kernel@...r.kernel.org
Cc:	Alan Cox <gnomes@...rguk.ukuu.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	Paul Burton <paul.burton@...tec.com>,
	Mans Rullgard <mans@...sr.com>,
	Joachim Eastwood <manabian@...il.com>,
	Scott Wood <scottwood@...escale.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Peter Ujfalusi <peter.ujfalusi@...com>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@...r.kernel.org>,
	"open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v7] serial: support for 16550A serial ports on LP-8x4x

On Tue, 2016-03-01 at 19:25 +0300, Sergei Ianovich wrote:
> On Tue, 2016-03-01 at 13:06 +0200, Andy Shevchenko wrote:
> > On Tue, 2016-03-01 at 00:26 +0300, Sergei Ianovich wrote:

> > > +	len &= 3;

Mask as well to be defined.

> > > +	len <<= 3;
> > 
> > Perhaps to define magic number (e.g. LP8841_DATA_LEN_SHIFT).
> 
> OK


> +	baud = tty_termios_baud_rate(termios);
> > > +
> > > +#ifdef BOTHER
> > > +	/* We only support fixed rates */

So, but if you support only fixed rates, why do you care about BOTHER
at all?

> > > 
> > I think you can call this unconditionally together with case >
> > 115200.
> 
> The calls are orthogonal. This one deals with the case when BOTHER is
> defined and set, and we have non-zero rate with BOTHER, but we have
> zero rate after BOTHER is cleared. So we set 9600 as a sane default
> speed.

> +
> > > +	/* We only support up to 115200 */
> > > +	if (baud > 115200) {
> > > +		baud = 115200;
> > > +		tty_termios_encode_baud_rate(termios, baud,
> > > baud);
> > > +	}
> 
> This one deals with the case when the rate is over 115200. If the
> previous case has been triggered, this one won't be.

Yeah, but I meant to unconditionally call it just once here every time.
 tty_termios_encode_baud_rate(termios, baud, baud);

> +static int lp8841_serial_probe(struct platform_device *pdev)
> > > +{
> > > +     struct uart_8250_port uart = {};
> > 
> > {0}
> 
> ---
> drivers/tty/serial/8250/8250_lp8841.c: In function
> 'lp8841_serial_probe':
> drivers/tty/serial/8250/8250_lp8841.c:124:32: warning: excess
> elements in struct initializer
>   struct uart_8250_port uart = {0};
>                                 ^
> drivers/tty/serial/8250/8250_lp8841.c:124:32: note: (near
> initialization for 'uart.port.lock.<anonymous>.rlock.raw_lock')

Do you have any warning verbosity enabled? I see a lot of stuff like
this in the code

$ git grep -n 'struct .* = {0};' | wc -l
338

$ git grep -n 'struct .* = { \?0 \?};' | wc -l
550

( '… = { 0 };' included)

> ---
> 
> Zero triggers a warning. I'll use memset().

Either will work.

> Thanks for lightning fast reviews. I'll resubmit v8 if there is no
> objections to the points above.

See above.

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy