linux-kernel - Re: [PATCH] serial: Do not treat the IIR register as a bitfield

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Date:   Thu, 30 Mar 2017 12:56:03 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Olliver Schinagl <oliver@...inagl.nl>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Stephen Warren <swarren@...dotorg.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Alexandre Courbot <gnurou@...il.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     dev@...ux-sunxi.org, Ed Blake <ed.blake@...tec.com>,
        Alexander Sverdlin <alexander.sverdlin@...ia.com>,
        Yegor Yefremov <yegorslists@...glemail.com>,
        Wan Ahmad Zainie <wan.ahmad.zainie.wan.mohamad@...el.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Jason Uy <jason.uy@...adcom.com>,
        Douglas Anderson <dianders@...omium.org>,
        Peter Hurley <peter@...leysoftware.com>,
        Tony Lindgren <tony@...mide.com>, Vignesh R <vigneshr@...com>,
        Thor Thayer <tthayer@...nsource.altera.com>,
        David Lechner <david@...hnology.com>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org, sparclinux@...r.kernel.org
Subject: Re: [PATCH] serial: Do not treat the IIR register as a bitfield

On Wed, 2017-03-29 at 20:44 +0200, Olliver Schinagl wrote:
> It seems that at some point, someone made the assumption that the UART
> Interrupt ID Register was a bitfield and started to check if certain
> bits where set.
> 
> Actually however the register contains interrupt ID's where only the
> MSB
> seems to be used singular and the rest share at least one bit. Thus
> doing bitfield operations is wrong.
> 
> This patch cleans up the serial_reg include file by ordering it and
> replacing the UART_IIR_ID 'mask' with a proper mask for the register.
> The OMAP uart appears to have used the two commonly 'reserved' bits 4
> and 5 and thus get an UART_IIR_EXT_MASK for these two bits.
> 
> This patch then goes over all UART_IIR_* users and changes the code
> from
> bitfield checking, to ID checking instead.


Looking to implementation I would rather go with some helper like

int serial_in_IIR(port, [additional mask])
{
 return port->serial_in(port, UART_IIR) & (_IIR_MASK [| additional
mask]);
}

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy