linux-kernel - Re: [PATCH v2 3/3] serial: core: Allow skipping old serial port initialization

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Message-ID: <CAGS+omCkKT9WHApnG+i+2Sn0zihBFV1ufuQn5+jfE3asuoTAEQ@mail.gmail.com>
Date:   Thu, 15 Mar 2018 00:23:31 +0000
From:   Daniel Kurtz <djkurtz@...omium.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        adurbin@...omium.org, linux-kernel@...r.kernel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, jslaby@...e.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        mbrugger@...e.com, dhowells@...hat.com, vigneshr@...com,
        sean@...s.org, Jeffy <jeffy.chen@...k-chips.com>,
        Doug Anderson <dianders@...omium.org>, matt.redfearn@...s.com,
        marc_gonzalez@...madesigns.com, linux-acpi@...r.kernel.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH v2 3/3] serial: core: Allow skipping old serial port initialization

On Wed, Mar 14, 2018 at 5:00 PM Kees Cook <keescook@...omium.org> wrote:

> On Wed, Mar 14, 2018 at 3:58 PM, Kees Cook <keescook@...omium.org> wrote:
> > On Wed, Mar 14, 2018 at 2:44 PM, Daniel Kurtz <djkurtz@...omium.org>
wrote:
> > Sorry for being dense. What tree is this against? I can't find mention
> > of amdcz in Linus's tree nor linux-next.

> As I watched this email send, I noticed the "3/3" in the Subject. ;) I
> see the amdcz support now. :P
> https://patchwork.kernel.org/project/LKML/list/?submitter=18441

> >> diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
> >> index a27ef5f56431..02570edaddd8 100644
> >> --- a/include/linux/serial_8250.h
> >> +++ b/include/linux/serial_8250.h
> >> @@ -136,6 +136,12 @@ struct uart_8250_port {
> >>         struct uart_8250_em485 *em485;
> >>  };
> >>
> >> +#ifdef CONFIG_SERIAL_8250
> >> +extern bool serial8250_skip_old_ports;
> >> +#else
> >> +static const bool serial8250_skip_old_ports;
> >> +#endif
> >
> > Where does serial8250_skip_old_ports get used where CONFIG_SERIAL_8250
> > isn't defined? (i.e. why is the #ifdef needed here?)

> This question still stands, though.

 From the same patch: https://patchwork.kernel.org/patch/10283641/

if (CONFIG_ACPI_SPCR_TABLE && !CONFIG_SERIAL_8250)

in other words, if serial ports are disabled, but we still want to parse
the APCI_SPCR_TABLE, which "defaults y if X86".
Perhaps that logic should be changed (no need to parse ACPI SPCR table if
we are going to disable serial anyway)?


> -Kees

> --
> Kees Cook
> Pixel Security