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Date:   Tue, 24 Oct 2023 10:10:16 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Crescent CY Hsieh <crescentcy.hsieh@moxa.com>
Cc:     Ilpo =?iso-8859-1?Q?J=E4rvinen?= <ilpo.jarvinen@linux.intel.com>,
        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
Message-ID: <2023102403-clash-utmost-8377@gregkh>
References: <20231018091739.10125-1-crescentcy.hsieh@moxa.com>
 <20231018091739.10125-7-crescentcy.hsieh@moxa.com>
 <f49feb43-e255-43bb-4271-8a13db2859fc@linux.intel.com>
 <ZTd2t9nsBx9pZKD9@moxa-ThinkCentre-M90t>
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On Tue, Oct 24, 2023 at 03:48:07PM +0800, Crescent CY Hsieh wrote:
> On Mon, Oct 23, 2023 at 12:25:18PM +0300, Ilpo Järvinen 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?

-ENODEV should be the proper one here.

thanks,

greg k-h