linux-kernel - Re: [RFC v2 0/4] Introduce i3c device userspace interface

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Message-ID: <20200217183747.6a18d6c4@collabora.com>
Date:   Mon, 17 Feb 2020 18:37:47 +0100
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Vitor Soares <Vitor.Soares@...opsys.com>
Cc:     Jose.Abreu@...opsys.com, Joao.Pinto@...opsys.com, arnd@...db.de,
        wsa@...-dreams.de, gregkh@...uxfoundation.org,
        bbrezillon@...nel.org, linux-kernel@...r.kernel.org,
        broonie@...nel.org, linux-i3c@...ts.infradead.org
Subject: Re: [RFC v2 0/4] Introduce i3c device userspace interface

On Mon, 17 Feb 2020 15:51:41 +0100
Boris Brezillon <boris.brezillon@...labora.com> wrote:

> Hello Vitor,
> 
> Sorry for taking so long to reply, and thanks for working on that topic.
> 
> On Wed, 29 Jan 2020 13:17:31 +0100
> Vitor Soares <Vitor.Soares@...opsys.com> wrote:
> 
> > For today there is no way to use i3c devices from user space and
> > the introduction of such API will help developers during the i3c device
> > or i3c host controllers development.
> > 
> > The i3cdev module is highly based on i2c-dev and yet I tried to address
> > the concerns raised in [1].
> > 
> > NOTES:
> > - The i3cdev dynamically request an unused major number.
> > 
> > - The i3c devices are dynamically exposed/removed from dev/ folder based
> >   on if they have a device driver bound to it.  
> 
> May I ask why you need to automatically bind devices to the i3cdev
> driver when they don't have a driver matching the device id
> loaded/compiled-in? If we get the i3c subsystem to generate proper
> uevents we should be able to load the i3cdev module and bind the device
> to this driver using a udev rule.

Hm, looks like we already send a proper MODALIAS [1], so we can actually
implement this auto-bind to i3cdev in udev (fall back on i3cdev
load+bind if no matching module is found).

[1]https://elixir.bootlin.com/linux/latest/source/drivers/i3c/master.c#L269