Re: [PATCH v3] USB: serial: xr: Add TIOCGRS485 and TIOCSRS485 ioctls

Jarkko Sonninen
2023-03-14T08:00:39Z

On 3/14/23 09:37, Greg Kroah-Hartman wrote:
> On Tue, Mar 14, 2023 at 09:00:01AM +0200, 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>
>> ---
>>
>> In this version only rs485.flags are stored to state.
>> There is no locking as only one bit of the flags is used.
>> ioctl returns -ENOIOCTLCMD as the actual error handling is in tty code.
> And the difference between previous versions? Take a look at the
> documentation for how to better describe version differences please.

I'll try to be more precise in the future.

>> + memset(&rs485, 0, sizeof(rs485));
> But you just copied this from userspace, why zero it out again? Is that
> to be expected (I really don't remember, sorry).

serial.h says

/*
* Serial interface for controlling RS485 settings on chips with suitable
* support. Set with TIOCSRS485 and get with TIOCGRS485 if supported by
your
* platform. The set function returns the new state, with any
unsupported bits
* reverted appropriately.
*/

This may mean only the flags, but I decided to zero the other
unsupported fields as well.

> Anyway, just minor comments, I'll let others review it as well.
>
> thanks,
>
> greg k-h

- Jarkko