linux-kernel - Re: [PATCH v3] tty: serial: don't do termios for BTIF

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Message-ID: <1592365859-26714-1-git-send-email-sean.wang@mediatek.com>
Date:   Wed, 17 Jun 2020 11:50:59 +0800
From:   <sean.wang@...iatek.com>
To:     <gregkh@...uxfoundation.org>
CC:     <andriy.shevchenko@...ux.intel.com>, <steven.liu@...iatek.com>,
        <arnd@...db.de>, <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <Ryder.Lee@...iatek.com>,
        <sean.wang@...iatek.com>, <tthayer@...nsource.altera.com>,
        <linux-serial@...r.kernel.org>, <jslaby@...e.com>,
        <matthias.bgg@...il.com>, <sr@...x.de>,
        <mika.westerberg@...ux.intel.com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3] tty: serial: don't do termios for BTIF

From: Sean Wang <sean.wang@...iatek.com>

>On Thu, Apr 23, 2020 at 02:02:08AM +0800, sean.wang@...iatek.com wrote:
>> From: Sean Wang <sean.wang@...iatek.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.
>
>Why does it matter?  If the connection isn't exported to userspace, who would run those termios functions on the port?

The bluetooth driver would use BTIF device as a serdev.

The termios function would be called in kernelspace from ttyport_open and then
to tty_set_termios defined in drivers/tty/serdev/serdev-ttyport.c.

>
>thanks,
>
>greg k-h