linux-kernel - Re: [PATCH] serial: core: Fix probing serial_base

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Message-ID: <20230601150706.GD14287@atomide.com>
Date:   Thu, 1 Jun 2023 18:07:06 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jiri Slaby <jirislaby@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Dhruva Gole <d-gole@...com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        John Ogness <john.ogness@...utronix.de>,
        Johan Hovold <johan@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-omap@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial: core: Fix probing serial_base_bus devices

* Greg Kroah-Hartman <gregkh@...uxfoundation.org> [230601 14:21]:
> On Thu, Jun 01, 2023 at 05:14:44PM +0300, Tony Lindgren wrote:
> > If a physical serial port device driver uses arch_initcall() we fail to
> > probe the serial_base_bus devices and the serial port tx fails. This is
> > because as serial_base_bus uses module_initcall().
> > 
> > Let's fix the issue by changing serial_base_bus to use arch_initcall().
> 
> This will only work if the linking order is such that this will always
> come before the drivers.  Is that the case here?

I guess based on Makefile. And also if serial drivers are modules as we
export uart_add_one_port() from serial_base.ko. But yeah this is pretty
fragile potentially.

Hmm maybe we could keep module_init() and then also call serial_base_init()
on uart_add_one_port() path if not yet initialized?

Probably the module_init() should be still there for case when no serial
port device drivers are loaded and serial_base is unloaded..

Regards,

Tony