Re: [PATCH v2] USB: serial: xr: Add TIOCGRS485 and TIOCSRS485 ioctls

Oliver Neukum
2023-03-13T09:54:11Z

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