linux-kernel - Re: [PATCH v2 1/3] i2c: add init

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: <aJyt2I1w6VYo1PPD@shell.armlinux.org.uk>
Date: Wed, 13 Aug 2025 16:23:04 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Gabor Juhos <j4g8y7@...il.com>, Wolfram Sang <wsa@...nel.org>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Andi Shyti <andi.shyti@...nel.org>, Andrew Lunn <andrew@...n.ch>,
	Hanna Hawa <hhhawa@...zon.com>,
	Robert Marko <robert.marko@...tura.hr>,
	Linus Walleij <linus.walleij@...aro.org>, linux-i2c@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Imre Kaloz <kaloz@...nwrt.org>, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/3] i2c: add init_recovery() callback

On Mon, Aug 11, 2025 at 11:17:41PM +0300, Andy Shevchenko wrote:
> On Mon, Aug 11, 2025 at 09:49:55PM +0200, Gabor Juhos wrote:
> > Add a new init_recovery() callback to struct 'i2c_bus_recovery_info'
> > and modify the i2c_init_recovery() function to call that if specified
> > instead of the generic i2c_gpio_init_recovery() function.
> > 
> > This allows controller drivers to skip calling the generic code by
> > implementing a dummy callback function, or alternatively to run a
> > fine tuned custom implementation.
> > 
> > This is needed for the 'i2c-pxa' driver in order to be able to fix
> > a long standing bug for which the fix will be implemented in a
> 
> > followup patch.
> 
> "...next change."
> 
> ...
> 
> The first traditional question is why the generic recovery is not working.

I opposed the conversion of my recovery code to generic recovery when
it was first mooted for this driver, and was over-ruled. Lo and behold,
as I predicted, generic recovery fails with i2c-pxa. I now don't
remember the details, but there has been a regression reported...

Given that I was over-ruled, I am not minded to go back and try and
find either the previous discussion (google can be exceedingly
difficult now to find such history) nor to try and work it out again
(I've other things, including meetings today.)

Nevertheless, all I now remember is that generic recovery breaks
i2c-pxa, whereas my recovery works.

If I had to guess, I suspect it's something to do with how careful I
was to ensure a glitchless transition between i2c mode and GPIO mode
on the pinmux, and the generic recovery probably isn't as careful, but
I could be wrong there.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!