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

[Jarkko Sonninen]

    Hello,

It uses only one flag from the struct from user. Would it be better to 
store only that to state ?

Do I need locking at all in that case ?

The whole struct is stored just in case, if someone would implement 
other functionality later.

    - Jarkko


Oliver Neukum kirjoitti 13/03/2023 klo 11.54:
> 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@xxxxxx>
>
>
> 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