linux-kernel - Re: [Patch v8 1/6] tty: add new helper function tty_get

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Date:   Tue, 21 Nov 2023 08:35:11 +0100
From:   Florian Eckert <fe@....tdt.de>
To:     Jiri Slaby <jirislaby@...nel.org>
Cc:     Eckert.Florian@...glemail.com, gregkh@...uxfoundation.org,
        pavel@....cz, lee@...nel.org, kabel@...nel.org,
        u.kleine-koenig@...gutronix.de, m.brock@...mierlo.com,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-leds@...r.kernel.org
Subject: Re: [Patch v8 1/6] tty: add new helper function tty_get_tiocm



On 2023-11-20 08:21, Jiri Slaby wrote:
> On 09. 11. 23, 9:50, Florian Eckert wrote:
>> There is no in-kernel function to get the status register of a tty 
>> device
>> like the TIOCMGET ioctl returns to userspace. Create a new function,
>> tty_get_tiocm(), to obtain the status register that other portions of 
>> the
>> kernel can call if they need this information, and move the existing
>> internal tty_tiocmget() function to use this interface.
>> 
>> Acked-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Signed-off-by: Florian Eckert <fe@....tdt.de>
>> ---
>>   drivers/tty/tty_io.c | 28 ++++++++++++++++++++++------
>>   include/linux/tty.h  |  1 +
>>   2 files changed, 23 insertions(+), 6 deletions(-)
>> 
>> diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
>> index 06414e43e0b5..e2e93404133e 100644
>> --- a/drivers/tty/tty_io.c
>> +++ b/drivers/tty/tty_io.c
>> @@ -2498,6 +2498,24 @@ static int send_break(struct tty_struct *tty, 
>> unsigned int duration)
>>   	return retval;
>>   }
>>   +/**
>> + * tty_get_tiocm - get tiocm status register
>> + * @tty: tty device
>> + *
>> + * Obtain the modem status bits from the tty driver if the feature
>> + * is supported.
>> + */
>> +int tty_get_tiocm(struct tty_struct *tty)
>> +{
>> +	int retval = -ENOTTY;
>> +
>> +	if (tty->ops->tiocmget)
>> +		retval = tty->ops->tiocmget(tty);
>> +
>> +	return retval;
> 
> Why not simply:

I just did it this way because it is also done this way in other 
functions
in this file.

> {
>  if (tty->ops->tiocmget)
>     return tty->ops->tiocmget(tty);
> 
>  return -ENOTTY;
> }

Of course, we could also do it this way. If this is the C style for the 
kernel,
then I will change it. Please give me a short feedback whether I should 
change it
and send a v9, or whether it is just a comment from you.

Best regards

Florian