linux-kernel - Re: [RFC] i2c-tools: i2ctransfer: add new tool

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 for Android: free password hash cracker in your pocket

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

Date:	Fri, 8 May 2015 23:40:42 +0200
From:	Jean Delvare <jdelvare@...e.de>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	linux-i2c@...r.kernel.org, linux-sh@...r.kernel.org,
	Magnus Damm <magnus.damm@...il.com>,
	Simon Horman <horms@...ge.net.au>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] i2c-tools: i2ctransfer: add new tool

Hi Wolfram,

On Fri, 8 May 2015 16:38:26 +0200, Wolfram Sang wrote:
> > Having slept over it, I came up with a 3rd proposal:
> > 
> > # i2ctransfer 0 w0x11@...0 0xc0 0xbd= r1@...1
> > 
> > That is, combining the slave address, direction and length into a
> > single parameter. The advantage is that this is all more explicit and
> > the risk of mixing up values is close to zero. Whether it is more or
> > less readable than the previous proposals is probably a matter of
> > taste. Also I suspect it would make the parsing and state machine more
> > simple, but that's only a nice side effect.
> > 
> > Wolfram (and others), please tell me what you think. I am not trying to
> > force my views here, just suggesting alternatives for your
> > consideration.
> 
> I liked your proposal, so thanks for this input. I agree that the risk
> of mixing something up is high, I was okay with the printout of the
> messages to be sent, but a better syntax is very welcome, too. I need to
> think about the flags a little bit, though. Although this isn't
> implemented yet, PEC and 10-bit flags might be added in the future?

This is a good point, we need to think about it. Maybe not PEC, as
normally any PEC-enabled transaction would be handled by the other
tools already. And I don't think the kernel can handle PEC over ioctl
I2C_RDWR anyway. But 10-bit addresses, we already had a request to
support than and your new tool would be perfect for that.

One easy way would be to assume that the transaction either targets one
or more 10-bit addressed chips, or one or more 7-bit addressed chips,
but doesn't mix. In that case a simple flag (say -t) in front of the
transaction will do the trick. I'd think it is sufficient, and I even
suspect that some controllers may only support that, but OTOH I never
worked with 10-bit addressed chips so I can't really tell.

If you think it's not enough, then the address modifier could go
separately before or after the address byte, i.e. either r1@...23t or
r1@...123. I suspect that the latter should be easier to implement.

> Handling R/W as "just another" flag made this option extremly simple.
> But we probably can work something out.

I think the proposal above makes more sense than grouping it with the
direction letter (r or w) even though it's also a letter, as it's
really an address modifier, which affects neither the direction nor the
length. But again it's really only a suggestion, if you can come up
with something clearer and/or easier to implement, please do.

> So much for the quick response, I'll have a closer look later.

I wouldn't call it "quick" ;-) but you're welcome.

-- 
Jean Delvare
SUSE L3 Support
--
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/