linux-kernel - Re: [PATCH 09/18] serial: sc16is7xx: add macro for max number of UART ports

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Date: Thu, 21 Dec 2023 11:41:03 -0500
From: Hugo Villeneuve <hugo@...ovil.com>
To: Andy Shevchenko <andriy.shevchenko@...el.com>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org, jringle@...dpoint.com,
 kubakici@...pl, phil@...pberrypi.org, linux-kernel@...r.kernel.org,
 linux-serial@...r.kernel.org, Hugo Villeneuve <hvilleneuve@...onoff.com>
Subject: Re: [PATCH 09/18] serial: sc16is7xx: add macro for max number of
 UART ports

On Wed, 20 Dec 2023 17:50:34 +0200
Andy Shevchenko <andriy.shevchenko@...el.com> wrote:

> On Tue, Dec 19, 2023 at 12:18:53PM -0500, Hugo Villeneuve wrote:
> > From: Hugo Villeneuve <hvilleneuve@...onoff.com>
> > 
> > Add macro to hold the maximum number of UART ports per IC/device.
> 
> ...
> 
> > -	if (count < 0 || count > ARRAY_SIZE(irda_port))
> > +	if (count < 0 || count > SC16IS7XX_MAX_PORTS)
> 
> ARRAY_SIZE() is more robust than this. What if you change to support different
> devices where this won't be as defined?

Hi,
not sure that I understand your point, because SC16IS7XX_MAX_PORTS is
the maximum for all devices supported by this driver. The irda_port
array always has a fixed number of elements set to SC16IS7XX_MAX_PORTS,
even if the device that we are probing has only one port for example.

But I can change it back to ARRAY_SIZE(irda_port) if you want.

> 
> >  		return;
> 
> ...
> 
> > -	if (count < 0 || count > ARRAY_SIZE(mctrl_port))
> > +	if (count < 0 || count > SC16IS7XX_MAX_PORTS)
> >  		return 0;
> 
> Ditto.
> 
> ...
> 
> > +	WARN_ON(devtype->nr_uart > SC16IS7XX_MAX_PORTS);
> 
> Not sure about this, perhaps it's fine.

This check is only there if we add support for a new device and we
incorrectly set nr_uart to an incorrect value, which will cause other
problems anyway, of course :)

This could be removed.

Hugo Villeneuve