linux-kernel - Re: [PATCH 1/2] regmap: allow busses to request formatting with specific endianness

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: <4FBD72A7.907@wwwdotorg.org>
Date:	Wed, 23 May 2012 17:28:39 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	linux-kernel@...r.kernel.org, Stephen Warren <swarren@...dia.com>
Subject: Re: [PATCH 1/2] regmap: allow busses to request formatting with specific
 endianness

On 05/23/2012 05:16 PM, Mark Brown wrote:
> On Wed, May 23, 2012 at 04:33:53PM -0600, Stephen Warren wrote:
> 
>> I'm not 100% sure if this is the approach you had in mind.
>> However, anything more all-encompassing would require separating
>> the concepts of endianness and
> 
> I wouldn't do this on the bus in the first instance, I'd do it on
> the device - it's pretty much orthogonal to the bus what the device
> wants and it's perfectly plausible that a device on another bus
> might've made unusual endiannness choices.  Otherwise it's pretty
> much what I was thinking of.
> 
> For MMIO I'd expect that a large proportion of devices on platform
> buses would pick native endianness.

I did briefly consider making this a property of regmap_config rather
than regmap_bus, but as you say, it'd mean every MMIO user would have
to specify the endianness value.

Also, it doesn't seem right for a device to be able to specify
register formatting endianness for MMIO; presumably we'd always want
that native.

Perhaps the solution is to have two fields; one for address formatting
(the endianness of which regmap-mmio.c will error-check is "native",
like it error-checks other fields) and a second for value
formatting/parsing, which I can see a device might want to influence
(e.g. to fix a byte swap in HW).

I suppose we could avoid every device having to specify the endianness
by introducing a fourth "DEFAULT" value == 0, and having the bus
define what default means - that way, I wouldn't have to edit any
drivers due to adding the regmap_bus field.

>> serialization that are coupled together in functions like 
>> regmap_format_4_12_write, and I'm not sure how that would work
>> conceptually.
> 
> Anything using format_write() can be ignored, it's already lost
> large chunks of functionality just from that.  Non-integer byte
> sizes cause issues.

--
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/