linux-kernel - Re: [PATCH 1/1] i2c-dev: switch from register

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Message-ID: <20160527111745.GA1663@katana>
Date:	Fri, 27 May 2016 13:17:45 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Erico Nunes <erico.nunes@...acom.ind.br>
Cc:	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] i2c-dev: switch from register_chrdev to cdev API

On Tue, May 03, 2016 at 03:45:43PM -0300, Erico Nunes wrote:
> i2c-dev had never moved away from the older register_chrdev interface to
> implement its char device registration. The register_chrdev API has the
> limitation of enabling only up to 256 i2c-dev busses to exist.
> 
> Large platforms with lots of i2c devices (i.e. pluggable transceivers)
> with dedicated busses may have to exceed that limit.
> In particular, there are also platforms making use of the i2c bus
> multiplexing API, which instantiates a virtual bus for each possible
> multiplexed selection.
> 
> This patch removes the register_chrdev usage and replaces it with the
> less old cdev API, which takes away the 256 i2c-dev bus limitation.
> It should not have any other impact for i2c bus drivers or user space.
> 
> This patch has been tested on qemu x86 and qemu powerpc platforms with
> the aid of a module which adds and removes 5000 virtual i2c busses, as
> well as validated on an existing powerpc hardware platform which makes
> use of the i2c bus multiplexing API.
> i2c-dev busses with device minor numbers larger than 256 have also been
> validated to work with the existing i2c-tools.
> 
> Signed-off-by: Erico Nunes <erico.nunes@...acom.ind.br>

Applied to for-next, thanks! I'll try to still get it into v4.7.


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