linux-kernel - Re: Page select register restrictions in regmap core

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: <44d4fce5-2ec9-4f62-b7ac-a317c7d843db@sirena.org.uk>
Date: Tue, 18 Jun 2024 18:45:09 +0100
From: Mark Brown <broonie@...nel.org>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, Armin Wolf <W_Armin@....de>
Subject: Re: Page select register restrictions in regmap core

On Tue, Jun 18, 2024 at 09:14:56AM -0700, Guenter Roeck wrote:

> Anyway, this may be all irrelevant in respect to regmap support.
> It turns out that at least some i801 controllers don't work with the
> access mechanism used by regmap, or maybe the spd5118 chips don't support
> I2C_FUNC_SMBUS_I2C_BLOCK. I already found that those chips don't support
> auto-incrementing the register address and actually reset the address on byte
> reads (i.e., subsequent calls to i2c_smbus_read_byte() always return the data
> from the first register). Since regmap doesn't have a means for me to say
> "don't use I2C_FUNC_SMBUS_I2C_BLOCK even if the controller supports it",
> I may have to drop regmap support entirely anyway. That would be annoying,
> but right now I have no idea how to work around that problem.

You can set the use_single_read and use_single_write flags in the config
to ensure registers are accessed one at a time, that restriction is
moderately common.

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)