linux-kernel - Re: [PATCH 3/6] serial: core: Add new prep

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Date:   Mon, 27 Sep 2021 16:05:47 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-serial@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] serial: core: Add new prep_tx for power management

On Fri, Sep 24, 2021 at 06:09:18PM +0300, Tony Lindgren wrote:
> * Johan Hovold <johan@...nel.org> [210924 14:38]:
> > On Thu, Sep 23, 2021 at 06:02:27PM +0300, Tony Lindgren wrote:

> > > > No need to be patching line disciplines for this.
> > > 
> > > Do you see issues with handling the errors in line disciplines?
> > 
> > It's just conceptually wrong to push retrying up the stack, possible all
> > the way to user space in case of non-blocking opens, just because the
> > device isn't already runtime active.
> 
> Yes, I don't see a way around that currently. Maybe if we start making
> use of uart_tx_stopped() or something similar that could be simplified.
> And we'll be still hit these line discipline error handling cases
> anyways depending on how long the serial port wake up takes.

I didn't really look at the ldisc change so not saying it isn't needed
for other reasons such as a full write buffer. But then I'd expect it to
be presented as a bug fix (perhaps it was).

Johan