linux-kernel - Re: [PATCH 0/3] serial: Fix support for UPF_SPD

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Message-ID: <Ysg2RW0B/cLL3k+k@kroah.com>
Date:   Fri, 8 Jul 2022 15:51:01 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Pali Rohár <pali@...nel.org>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Johan Hovold <johan@...nel.org>,
        Marek Behún <kabel@...nel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] serial: Fix support for UPF_SPD_* flags

On Fri, Jul 08, 2022 at 03:26:21PM +0200, Pali Rohár wrote:
> On Friday 08 July 2022 15:07:43 Greg Kroah-Hartman wrote:
> > On Thu, Jul 07, 2022 at 10:48:40AM +0200, Pali Rohár wrote:
> > > On Friday 22 April 2022 16:28:06 Greg Kroah-Hartman wrote:
> > > > On Tue, Mar 22, 2022 at 04:29:08PM +0200, Andy Shevchenko wrote:
> > > > > On Mon, Mar 21, 2022 at 11:07 PM Pali Rohár <pali@...nel.org> wrote:
> > > > > >
> > > > > > Support for UPF_SPD_* flags is currently broken in more drivers for two
> > > > > > reasons. First one is that uart_update_timeout() function does not
> > > > > 
> > > > > the uart_update_timeout()
> > > > > 
> > > > > > calculate timeout for UPF_SPD_CUST flag correctly. Second reason is that
> > > > > > userspace termios structre is modified by most drivers after each
> > > > > 
> > > > > structure
> > > > > 
> > > > > ...
> > > > > 
> > > > > > (error handling was ommited for simplification)
> > > > > 
> > > > > omitted
> > > > > 
> > > > > > After calling set_active_spd_cust_baud() function SPD custom divisor
> > > > > > should be active and therefore is_spd_cust_active() should return true.
> > > > > >
> > > > > > But it is not active (cfgetospeed does not return B38400) and this patch
> > > > > > series should fix it. I have tested it with 8250 driver.
> > > > > 
> > > > > drivers
> > > > > 
> > > > > > Originally Johan Hovold reported that there may be issue with these
> > > > > > ASYNC_SPD_FLAGS in email:
> > > > > > https://lore.kernel.org/linux-serial/20211007133146.28949-1-johan@kernel.org/
> > > > > >
> > > > > >
> > > > > > Johan, Greg, could you please test these patches if there is not any
> > > > > > regression?
> > > > > 
> > > > > I'm wondering why we are still supporting this ugly hack?
> > > > > Doesn't BOTHER work for you?
> > > > 
> > > > Yes, I too do not want to add more support for these old flags.  If they
> > > > have not been working, let's not add support for them as obviously no
> > > > one is using them.  Let's try to remove them if at all possible.
> > > 
> > > Well, it works partially. For more drivers SET method is working, but
> > > GET method returns incorrect value. If your userspace application is
> > > written in a way that does not retrieve from kernel current settings
> > > then it has big probability that application works.
> > 
> > I do not understand, sorry, what do you mean by this?
> 
> I mean that SET methods are working, GET methods not. In this case SET
> done via ioctl(TIOCSSERIAL) and GET via ioctl(TIOCGSERIAL).
> 
> > And as you are responding to a months-old thread, I am totally lost, and
> > don't even know what the patch here was...
> > 
> > > So, do you really want to remove support for these old flags completely?
> > > That would of course break above applications.
> > 
> > I'm not saying remove them, I'm saying let us not add any more
> > dependancies on them in order to keep new applications from ever wanting
> > to use them.
> 
> Last time you wrote to remove them. Now saying not to remove them. So I
> do not understand you now.

I'm sorry, I am totally lost.  How about starting over and resubmitting
the changes you want and we can go from there.

greg k-h