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Date:   Mon, 13 Mar 2023 10:54:01 +0100
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Subject: Re: [PATCH v2] USB: serial: xr: Add TIOCGRS485 and TIOCSRS485 ioctls
To:     Jarkko Sonninen <kasper@iki.fi>
Cc:     Johan Hovold <johan@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
References: <ZA7Wh2Z/DdKOsOYr@kroah.com>
 <20230313082734.886890-1-kasper@iki.fi>
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From:   Oliver Neukum <oneukum@suse.com>
In-Reply-To: <20230313082734.886890-1-kasper@iki.fi>
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On 13.03.23 09:27, Jarkko Sonninen wrote:
> Add support for RS-485 in Exar USB adapters.
> RS-485 mode is controlled by TIOCGRS485 and TIOCSRS485 ioctls.
> Gpio mode register is set to enable RS-485.
> 
> Signed-off-by: Jarkko Sonninen <kasper@iki.fi>


Hi,

I am sorry, but locking is really broken here. All these contexts can sleep.
There is no need for a spinlock. As far as you need locking, just use a mutex.

Secondly, if xr_set_rs485_config() needs locking, so will xr_get_rs485_config()
or you can get the case that you return half a new and half an old state to user
space.

	Regards
		Oliver