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Subject: Re: [PATCH v3 0/2] Bluetooth: Add NULL check for tiocmget() and
 tiocmset()
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <20190206063533.GA7402@myunghoj-Precision-5530>
Date:   Wed, 6 Feb 2019 08:06:54 +0100
Cc:     Johan Hedberg <johan.hedberg@gmail.com>,
        linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org
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Message-Id: <AD78221A-2ABE-4BC2-A63A-F706FD5BC2FE@holtmann.org>
References: <cover.1549346039.git.mhjungk@gmail.com>
 <0D421861-FCD6-4AFF-8A0F-DBEE520DB64B@holtmann.org>
 <20190206063533.GA7402@myunghoj-Precision-5530>
To:     Myungho Jung <mhjungk@gmail.com>
Sender: linux-bluetooth-owner@vger.kernel.org
Precedence: bulk

Hi Myungho,

>>> tiocmget() and tiocmset() operations are optional and some tty drivers
>>> like pty miss the operations. Add NULL checks to prevent from
>>> dereference.
>>> 
>>> Myungho Jung (2):
>>> Bluetooth: hci_ath: Add NULL check for tiocmget() and tiocmset() in
>>>   ath_setup()
>>> Bluetooth: hci_ldisc: Add NULL check for tiocmget() and tiocmset() in
>>>   hci_uart_set_flow_control()
>>> 
>>> drivers/bluetooth/hci_ath.c   | 6 ++++++
>>> drivers/bluetooth/hci_ldisc.c | 4 ++++
>>> 2 files changed, 10 insertions(+)
>> 
>> why are we not enforcing the availability of these in the hci_uart_tty_open?
> 
> Are the operations required on any HCI UART drivers? For now, I found only 5
> drivers (ath, bcm, intel, mrvl, and qca) are explicitly calling them. So, I'm
> not sure whether it breaks any existing code with other drivers if returning
> error in open().

the H:4 spec requires setting flow control. In some cases this is done by the hciattach or btattach utility, but it still means that it is required. So failing on TTYs that don’t support it is just fine.

Regards

Marcel