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Date:   Tue, 24 Oct 2023 15:48:07 +0800
From:   Crescent CY Hsieh <crescentcy.hsieh@moxa.com>
To:     Ilpo =?iso-8859-1?Q?J=E4rvinen?= <ilpo.jarvinen@linux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-serial <linux-serial@vger.kernel.org>
Subject: Re: [PATCH v3 6/6] tty: serial: 8250: Add support for MOXA PCIe
 boards to switch interface between RS422/RS485
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On Mon, Oct 23, 2023 at 12:25:18PM +0300, Ilpo J?rvinen wrote:
> On Wed, 18 Oct 2023, Crescent CY Hsieh wrote:
> > +		/*
> > +		 * RS232 is not supported for MOXA PCIe boards with device IDs
> > +		 * matching the pattern 0x*3**.
> > +		 */
> > +		if (pci_moxa_match_second_digit(device, 0x0300))
> > +			return -EOPNOTSUPP;
> 
> This is not the correct error code I think. Maybe return -ENXIO instead.

I think EOPNOTSUPP or ENOTSUPP would be more reasonable, they directly
indicates "operation is not supported".

However, EOPNOTSUPP is used for network-related and ENOTSUPP is used for
NFSv3 protocol, even though they are already been used throughout the
kernel.

Maybe add a new one stand for serial, or clean them up into a general
one, or use EOPNOTSUPP and ENOTSUPP just for now?

---
Sincerely,
Crescent CY Hsieh