linux-kernel - Re: [PATCH v4 2/3] tty: add new helper function tty_get

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Date:   Sun, 22 Oct 2023 12:24:45 +0200
From:   Florian Eckert <fe@....tdt.de>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Eckert.Florian@...glemail.com, jirislaby@...nel.org, pavel@....cz,
        lee@...nel.org, kabel@...nel.org, u.kleine-koenig@...gutronix.de,
        ansuelsmth@...il.com, m.brock@...mierlo.com,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-leds@...r.kernel.org
Subject: Re: [PATCH v4 2/3] tty: add new helper function tty_get_tiocm


On 2023-10-21 18:15, Greg KH wrote:
> On Thu, Oct 19, 2023 at 01:28:08PM +0200, Florian Eckert wrote:
>> The struct 'tty_struct' has a callback to read the status flags of the 
>> tty
>> if the tty driver provides them. So fare, the data is transferred 
>> directly
>> to userspace with the function 'tty_tiocmget'. This function cannot be
>> used to evaluate the status line of the tty interface in the 
>> ledtrig-tty
>> trigger. To make this possible, a new function must be added that does
>> not immediately pass the data on to userspace.
>> 
>> The new function 'tty_get_tiocm' only returns the status register.
>> This information can then be processed further in the ledtrig-tty
>> trigger.
> 
> Writing changelogs are hard.  You are including a lot of information in
> here that really doesn't need to be, as you are focusing on your
> specific use case, which is fine, but you are creating a generic
> function.

Yes, that is absolutely right. I'll try to take that into account next
time, thanks for your advice.

> This can be simpler, how about something like this:
> 
> 	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.

I will replace the commit message with your suggestion in the next round 
of
the patch series. Thanks!

---
Florian