linux-kernel - Re: [PATCH v2 2/3] serial: 8250: Store whether fifo device is enabled

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Date: Tue, 16 Apr 2024 22:18:31 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Michael Pratt <mcpratt@...me>
Cc: linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Wander Lairson Costa <wander@...hat.com>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Vamshi Gajjela <vamshigajjela@...gle.com>
Subject: Re: [PATCH v2 2/3] serial: 8250: Store whether fifo device is enabled

On Tue, Apr 16, 2024 at 07:09:52PM +0000, Michael Pratt wrote:
> On Tuesday, April 16th, 2024 at 14:55, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> > > @@ -3392,6 +3392,8 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
> > 
> > > + up->fifo_enable = use_fifo;
> > 
> > This seems incorrect / not the only one place to assign this. What if the
> > console not enabled at compile time? What if it's not enabled at boot time?
> 
> This is 8250 specific, and currently, it's the only place there
> where it's decided whether or not to use the fifo device
> by checking a bunch of flags and values.

Exactly, as initial commit is related to the kernel console _only_.
While your code, IIUC (correct me, if I'm wrong) is for any use of the port.

> If you're suggesting that these checks are moved out of this function somewhere else,
> I would probably agree with that, but let's save that idea for the future...

Not really (again, IIUC above), as console can be not enabled, and hence
serial8250_console_write() never been called and you will have false impression
that there is no FIFO in use.

> If you're suggesting that there could be a null pointer, I don't think that's possible
> in this function... (the name of the pointer being "up" might be confusing?)
> 
> Sorry if I'm misunderstanding what you mean.

-- 
With Best Regards,
Andy Shevchenko