linux-kernel - Re: [PATCH 1/2] serial: 8250: Allow port registration without UPF_BOOT

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Message-ID: <20190426215103.GD9224@smile.fi.intel.com>
Date:   Sat, 27 Apr 2019 00:51:03 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Esben Haabendal <esben@...bendal.dk>
Cc:     linux-serial@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Darwin Dingel <darwin.dingel@...iedtelesis.co.nz>,
        He Zhe <zhe.he@...driver.com>,
        Jisheng Zhang <Jisheng.Zhang@...aptics.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] serial: 8250: Allow port registration without
 UPF_BOOT_AUTOCONF

On Fri, Apr 26, 2019 at 06:54:05PM +0200, Esben Haabendal wrote:
> Andy Shevchenko <andriy.shevchenko@...ux.intel.com> writes:
> > On Fri, Apr 26, 2019 at 10:40:37AM +0200, Esben Haabendal wrote:
> >> With serial8250_register_8250_port() forcing UPF_BOOT_AUTOCONF bit on, it
> >> is not possible to register a port without having
> >> serial8250_request_std_resource() called.
> >> 
> >> For adding a 8250 port to an MFD device, this is problematic, as the
> >> request_mem_region() call will fail, as the MFD device (and rightly  so)
> >> has requested the region.  For this case, the 8250 port should accept
> >> having passed mapbase and membase, and just use that.
> >
> > You need to simple set port type and use UPF_FIXED_TYPE.
> > No need for this patch.
> 
> The reason for this patch is to be able to do exactly that (set port
> type and UPF_FIXED_TYPE) without having UPF_BOOT_AUTOCONF added.
> 
> In the current serial8250_register_8250_port() there is:
> 
>     uart->port.flags        = up->port.flags | UPF_BOOT_AUTOCONF;
> 
> So, even though I set UPF_FIXED_TYPE, I get
> UPF_FIXED_TYPE|UPF_BOOT_AUTOCONF. 

Yes.

> So I need this patch.

Why? I don't see any problems to have these flags set. Moreover, some drivers
are used as MFD counterparts with exactly same bits set.

> I think it is unfortunate that UPF_BOOT_AUTOCONF is or'ed to flags like
> that, but changing that will surely break stuff.

True.

-- 
With Best Regards,
Andy Shevchenko