linux-kernel - Re: [PATCH] i2c: piix4: Fix request

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Message-ID: <CAPybu_3prZYuGcHKx-ppm9_viKVm-VzgR6ou=O7vPiA0ocX16g@mail.gmail.com>
Date:   Mon, 30 Jan 2017 02:11:47 +0100
From:   Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
To:     Jean Delvare <jdelvare@...e.de>
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-i2c@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: piix4: Fix request_region size

Hi Jean and Wolfram



On Sat, Jan 28, 2017 at 12:13 PM, Jean Delvare <jdelvare@...e.de> wrote:
> Hi Wolfram,
>
> On Sat, 28 Jan 2017 12:00:21 +0100, Wolfram Sang wrote:
>>
>> > >  /* count for request_region */
>> > > -#define SMBIOSIZE        8
>> > > +#define SMBIOSIZE        9
>> >
>> > Are you certain that all supported devices have this extra register?
>>
>> Isn't it better to have a potentially unused register mapped than a
>> potentially used register unmapped

We have been  "lucky" that it is a ioport and not a mmap region,
otherwise we would have seen a nice oops :).

>
> My concern is that the region request could fail due to a conflict with
> another device, if the physical I/O region is only 8 and we try to
> request 9.

I do not think that this is the case, if you check the top of the file
you can see how there are many other definitions for registers. I
expect that SMBIOSIZE=8 is just the original author being
conservative.

Of course I cannot say that there is one platform where one extra
ioport can cause a conflict, but I believe that we must request all
the ports that we will use.


Regards!
>
> --
> Jean Delvare
> SUSE L3 Support



-- 
Ricardo Ribalda