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Date: Wed, 21 Feb 2024 10:47:13 -0800
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Subject: Re: [PATCH v1 02/14] serial: core: Add UPIO_UNSET constant for unset
 port type
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To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Thomas Gleixner <tglx@linutronix.de>, linux-kernel@vger.kernel.org,
 linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
 linux-aspeed@lists.ozlabs.org, linux-rpi-kernel@lists.infradead.org,
 linux-mips@vger.kernel.org, linux-tegra@vger.kernel.org
Cc: Jiri Slaby <jirislaby@kernel.org>, Joel Stanley <joel@jms.id.au>,
 Andrew Jeffery <andrew@codeconstruct.com.au>,
 Florian Fainelli <florian.fainelli@broadcom.com>, Ray Jui
 <rjui@broadcom.com>, Scott Branden <sbranden@broadcom.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@broadcom.com>, Al Cooper <alcooperx@gmail.com>,
 =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>,
 Paul Cercueil <paul@crapouillou.net>, Vladimir Zapolskiy <vz@mleia.com>,
 Thierry Reding <thierry.reding@gmail.com>,
 Jonathan Hunter <jonathanh@nvidia.com>,
 Kunihiko Hayashi <hayashi.kunihiko@socionext.com>,
 Masami Hiramatsu <mhiramat@kernel.org>
References: <20240221183442.4124354-1-andriy.shevchenko@linux.intel.com>
 <20240221183442.4124354-3-andriy.shevchenko@linux.intel.com>
From: Florian Fainelli <f.fainelli@gmail.com>
In-Reply-To: <20240221183442.4124354-3-andriy.shevchenko@linux.intel.com>
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On 2/21/24 10:31, Andy Shevchenko wrote:
> In some APIs we would like to assign the special value to iotype
> and compare against it in another places. Introduce UPIO_UNSET
> for this purpose.
> 
> Note, we can't use 0, because it's a valid value for IO port access.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>   include/linux/serial_core.h | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> index 2d2ec99eca93..2b0526ae1fac 100644
> --- a/include/linux/serial_core.h
> +++ b/include/linux/serial_core.h
> @@ -470,6 +470,7 @@ struct uart_port {
>   
>   	unsigned char		iotype;			/* io access style */
>   
> +#define UPIO_UNSET		((unsigned char)~0U)	/* UCHAR_MAX */

Nit: I would name this UPIO_UNKNOWN, or UPIO_NOTSET, unset means to me 
that it was previously set and we undid that action, whereas unknown or 
not set means we never did.
-- 
Florian