linux-kernel - Re: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CACxGe6tjyx3GTgNgMRtvwhrFsTGizkeTqY_N6=2gdQjvMSD8Ug@mail.gmail.com>
Date:	Wed, 6 Feb 2013 10:03:44 +0000
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
	Michal Simek <monstr@...str.eu>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	dahinds@...rs.sourceforge.net
Subject: Re: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)_le16
 with generic iowrite(read)8/16(be)

On Tue, Feb 5, 2013 at 3:12 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Tuesday 05 February 2013 18:03:31 Alexey Brodkin wrote:
>> The Xilinx System ACE Compact Flash chip is a true little-endian device
>> and the PLB is a big-endian bus. Therefore the XPS System ACE Interface
>> Controller will do a bit-swap in each byte when connecting the PLB data
>> bus to the System ACE data bus as shown in Table 2.
>>
>> Note however, that the XPS System ACE Interface Controller does not
>> perform the byte swapping necessary to interface to a little-endian
>> device when configured to use 16-bit mode. Therefore, the software
>> drivers provided for this core will perform the necessary byte-swapping
>> to correctly interface to the Xilinx System ACE Compact Flash chip as
>> shown in Table 3.
>
> Ok. In this case, I would recommend making the default for this driver
> little-endian, and adding a quirk for broken hardware bridges like the
> one you cited to have a mixed-endian mode if configured so at compile
> time.
>
> It seems that on all normal platforms, this device should behave as
> little-endian, while the Xilinx bridge can be either big-endian
> or little-endian, depending on whether it is used in 8-bit or 16-bit
> mode, so if we are using this, it cannot be known at compile time.

The driver already handles this. It has three sets of accessors;
8-bit, 16-bit LE and 16-bit BE *and* when doing 16-bit it figures out
on its own which set to use at runtime. There is nothing controversial
here. The only problem is that the driver is currently using in_/out_
IO accessors instead of ioread/iowrite variants.

g.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/