linux-kernel - Re: [PATCH v4 9/9] i2c: atr: add passthrough flag

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Message-ID: <20250430163617.3edeedf2@booty>
Date: Wed, 30 Apr 2025 16:36:17 +0200
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Cosmin Tanislav <demonsingur@...il.com>
Cc: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, Wolfram Sang
 <wsa+renesas@...g-engineering.com>, Mauro Carvalho Chehab
 <mchehab@...nel.org>, Romain Gantois <romain.gantois@...tlin.com>, Arnd
 Bergmann <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org
Subject: Re: [PATCH v4 9/9] i2c: atr: add passthrough flag

On Mon, 28 Apr 2025 13:25:14 +0300
Cosmin Tanislav <demonsingur@...il.com> wrote:

> Some I2C ATRs can have other I2C ATRs as children. The I2C messages of
> the child ATRs need to be forwarded as-is if the parent I2C ATR can
> only do static mapping.
> 
> In the case of GMSL, the deserializer I2C ATR actually doesn't have I2C
> address remapping hardware capabilities, but it is able to select which
> GMSL link to talk to, allowing it to change the address of the
> serializer.
> 
> The child ATRs need to have their alias pools defined in such a way to
> prevent overlapping addresses between them, but there's no way around
> this without orchestration between multiple ATR instances.
> 
> To allow for this use-case, add a flag that allows unmapped addresses
> to be passed through, since they are already remapped by the child ATRs.
> 
> There's no case where an address that has not been remapped by the child
> ATR will hit the parent ATR.
> 
> Signed-off-by: Cosmin Tanislav <demonsingur@...il.com>

Reviewed-by: Luca Ceresoli <luca.ceresoli@...tlin.com>

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com