linux-kernel - Re: [PATCH v10 1/3] serdev: Add method to assert break signal over tty UART port

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Date:   Tue, 14 Mar 2023 11:35:07 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Neeraj Sanjay Kale <neeraj.sanjaykale@....com>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, marcel@...tmann.org,
        johan.hedberg@...il.com, luiz.dentz@...il.com,
        gregkh@...uxfoundation.org, jirislaby@...nel.org,
        alok.a.tiwari@...cle.com, hdanton@...a.com,
        ilpo.jarvinen@...ux.intel.com, leon@...nel.org,
        netdev@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        linux-serial@...r.kernel.org, amitkumar.karwar@....com,
        rohit.fule@....com, sherry.sun@....com
Subject: Re: [PATCH v10 1/3] serdev: Add method to assert break signal over
 tty UART port

On Mon, Mar 13, 2023 at 08:10:26PM +0530, Neeraj Sanjay Kale wrote:
> Adds serdev_device_break_ctl() and an implementation for ttyport.
> This function simply calls the break_ctl in tty layer, which can
> assert a break signal over UART-TX line, if the tty and the
> underlying platform and UART peripheral supports this operation.
> 
> Signed-off-by: Neeraj Sanjay Kale <neeraj.sanjaykale@....com>
> ---
> v3: Add details to the commit message. Replace ENOTSUPP with
> EOPNOTSUPP. (Greg KH, Leon Romanovsky)
> v9: Replace all instances of ENOTSUPP with EOPNOTSUPP.
> (Simon Horman)

I'm all for this change. But perhaps it should be a separate clean-up patch,
that precedes the feature-patch which adds the new method. I think that
would make things a bit clearer.

...

> diff --git a/include/linux/serdev.h b/include/linux/serdev.h
> index 66f624fc618c..c065ef1c82f1 100644
> --- a/include/linux/serdev.h
> +++ b/include/linux/serdev.h

...

> @@ -202,6 +203,7 @@ int serdev_device_write_buf(struct serdev_device *, const unsigned char *, size_
>  void serdev_device_wait_until_sent(struct serdev_device *, long);
>  int serdev_device_get_tiocm(struct serdev_device *);
>  int serdev_device_set_tiocm(struct serdev_device *, int, int);
> +int serdev_device_break_ctl(struct serdev_device *serdev, int break_state);
>  void serdev_device_write_wakeup(struct serdev_device *);
>  int serdev_device_write(struct serdev_device *, const unsigned char *, size_t, long);
>  void serdev_device_write_flush(struct serdev_device *);
> @@ -255,6 +257,10 @@ static inline int serdev_device_set_tiocm(struct serdev_device *serdev, int set,
>  {
>  	return -ENOTSUPP;

It seems that you might have missed at least this one.

>  }
> +static inline int serdev_device_break_ctl(struct serdev_device *serdev, int break_state)
> +{
> +	return -EOPNOTSUPP;
> +}
>  static inline int serdev_device_write(struct serdev_device *sdev, const unsigned char *buf,
>  				      size_t count, unsigned long timeout)
>  {
> -- 
> 2.34.1
>