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Date: Mon, 27 Jul 2026 14:03:20 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Cc: Sagi Maimon <maimon.sagi@gmail.com>, jonathan.lemon@gmail.com,
 richardcochran@gmail.com, andrew+netdev@lunn.ch, davem@davemloft.net,
 edumazet@google.com, pabeni@redhat.com, linux-kernel@vger.kernel.org,
 netdev@vger.kernel.org
Subject: Re: [PATCH v6] ptp: ocp: add CPLD ISP support for ADVA TimeCard X1
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On Mon, 27 Jul 2026 12:02:53 +0100 Vadim Fedorenko wrote:
> I don't like the idea of having a buffer in a global structure. And it
> doesn't look like you can actually serialize access. Imaging 2 processes
> manipulating this i2c bus. I can be that mutex will put them like:
> 
> 1. process1 -> write cmd
> 2. process2 -> write cmd
> 3. process1 -> read result
> 
> That means the data will be a mess.
> 
> That's why it is a really bad thing to allow direct access from the user
> space. Is it possible to add a property per command?

At a glance - adding I2C support via 2 magic files in sysfs is rather
odd. Either expose a real i2c bus or make the driver sends the
appropriate commands. We are opposed to raw device write interfaces in
netdev.