linux-kernel - Re: [PATCH 1/2] mux: add mux_chip

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] [day] [month] [year] [list]

Message-ID: <f9e56af4-3474-91d0-aa43-eb1a582a8074@axentia.se>
Date: Sat, 7 Sep 2024 11:16:12 +0200
From: Peter Rosin <peda@...ntia.se>
To: Thomas Richard <thomas.richard@...tlin.com>
Cc: linux-kernel@...r.kernel.org, gregory.clement@...tlin.com,
 theo.lebrun@...tlin.com, thomas.petazzoni@...tlin.com, u-kumar1@...com,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 1/2] mux: add mux_chip_resume() function

Hi!

2024-09-06 at 18:17, Thomas Richard wrote:
> On 9/5/24 10:28, Peter Rosin wrote:
>> Maybe you should simply implement resume locally in the driver itself and
>> have it reprogram the register, perhaps still based on mux->cached_state,
>> but "behind the back" of the mux core?
> 
> Ok, it's seems to be the best solution for now.
> I'll send a patch.
> 
> Just a small comment, I think I should not use the cached_state.
> I should implement a mux_mmio_get(), which is called during suspend, to
> get the "real" state. Then use it during resume.
> Because the cache is not coherent during is a very small period [1].
> 
> What do you think ?
> 
> [1]
> https://elixir.bootlin.com/linux/v6.11-rc6/source/drivers/mux/core.c#L144

If you are worried about that, then I think you need a mutex in the
driver. Or why wouldn't a mux_mmio_get() be racy as well? (since you
are not able to grab the mux->lock)

Cheers,
Peter