linux-kernel - Re: [PATCH v12 7/9] ACPI: Translate the I/O range of non-MMIO devices before scanning

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Message-ID: <62634aa6-ad3c-93c2-e6fa-9e163d4004ca@huawei.com>
Date:   Mon, 5 Feb 2018 14:25:20 +0000
From:   John Garry <john.garry@...wei.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Rob Herring <robh+dt@...nel.org>,
        "Bjorn Helgaas" <bhelgaas@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Mark Rutland <mark.rutland@....com>,
        Olof Johansson <olof@...om.net>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        <dann.frazier@...onical.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linuxarm <linuxarm@...wei.com>, <linux-pci@...r.kernel.org>,
        Corey Minyard <minyard@....org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux-Arch <linux-arch@...r.kernel.org>,
        "Randy Dunlap" <rdunlap@...radead.org>
Subject: Re: [PATCH v12 7/9] ACPI: Translate the I/O range of non-MMIO devices
 before scanning

On 05/02/2018 13:16, Andy Shevchenko wrote:
> On Thu, Feb 1, 2018 at 1:32 PM, John Garry <john.garry@...wei.com> wrote:
>
>

Hi Andy,

> I'm not going through all patch, by one thing I would like you to pay
> attention on, i.e.
> printing resource_size_t and struct resource
>
>>> +               dev_err(dev, "translate bus-addr(0x%llx) fail!\n",
>>> +                       resource->start);
>
> resource_size_t is dynamic width type, you will see a compiler
> warning. For this we have
> %pap specifier.
>
> Moreover, in some cases it's useful to print struct resource via %pR or %pr.

I have already fixed this up in my rework.

>
> Consider reading kernel documentation about these (printk-formats.rst).
>
>>> +struct acpi_indirectio_host_data {
>>> +       resource_size_t io_size;
>>> +       resource_size_t io_start;
>>> +};
>
> Why not utilize struct resource?
>
> If it's coming from platform / firmware it should *never* have types
> like size_t, unsigned long, resource_size_t, etc.

This is not coming from firmware, but it is a struct which we define in 
the kernel per host, describing that host bus address range for translation.

In fact, generally io_start is 0 and the io_size would be 
PIO_INDIRECT_SIZE, so I'll consider removing it for now.

>
>>> +/* All the host devices which apply indirect-IO can be listed here. */
>>> +static const struct acpi_device_id acpi_indirect_host_id[] = {
>>> +       {""},
>>> +};
>
> The idea of terminator is to be such (remove comma there). And it's
> basically redundant to have an empty string there. Moreover, it's a
> waste of resources in ro section.

OK, the comma should be removed. So what is the preferred acpi device id 
array sentinel? I see {}, {"", 0}, and {""} used.

>

thank you,
John