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Date:   Mon, 20 Apr 2020 13:46:24 +0300
From:   Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To:     sean.wang@mediatek.com
Cc:     gregkh@linuxfoundation.org, jslaby@suse.com,
        robert.jarzmik@free.fr, arnd@arndb.de, p.zabel@pengutronix.de,
        joel@jms.id.au, david@lechnology.com, jan.kiszka@siemens.com,
        heikki.krogerus@linux.intel.com, hpeter@gmail.com, vigneshr@ti.com,
        matthias.bgg@gmail.com, tthayer@opensource.altera.com,
        linux-mediatek@lists.infradead.org, linux-serial@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Steven Liu <steven.liu@mediatek.com>,
        Ryder Lee <ryder.lee@mediatek.com>
Subject: Re: [PATCH v2] tty: serial: don't do termios for BTIF
Message-ID: <20200420104624.GM185537@smile.fi.intel.com>
References: <8c47aea3aa3cce4d7484b840ddb117cd16bcf1cc.1587347988.git.sean.wang@mediatek.com>
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On Mon, Apr 20, 2020 at 10:06:38AM +0800, sean.wang@mediatek.com wrote:
> From: Sean Wang <sean.wang@mediatek.com>
> 
> Bluetooth Interface (BTIF) is designed dedicatedly for MediaTek SOC with
> BT in order to be instead of the UART interface between BT module and Host
> CPU, and not exported to user space to access.
> 
> As the UART design, BTIF will be an APB slave and can transmit or receive
> data by MCU access, but doesn't provide termios function like baudrate and
> flow control setup.
> 
> Even LCR on offset 0xC that is just a FAKELCR
> a. If FAKELCR[7] is equaled to 1, RBR(0x00), THR(0x00), IER(0x04)
>    will not be readable/writable.
> 
> b. If FAKELCR is equaled to 0xBF, RBR(0x00), THR(0x00), IER(0x04),
>    IIR(0x08), and LSR(0x14) will not be readable/writable.
> 
> So adding a new capability 'UART_CAP_NMOD' for the unusual unsupported
> case.

...

> +#define UART_CAP_NMOD	(1 << 18)	/* UART doesn't do termios */

I would rather spell it as NTIO or NO_TIO (as TIO is a well established prefix
for termios IOCTLs).


-- 
With Best Regards,
Andy Shevchenko