Re: [PATCH v3 0/5] Introduce i3c device userspace interface

From: Boris Brezillon <boris.brezillon@collabora.com>
To: Vitor Soares <Vitor.Soares@synopsys.com>
Cc: Jose Abreu <Jose.Abreu@synopsys.com>,
	"corbet@lwn.net" <corbet@lwn.net>,
	Joao Pinto <Joao.Pinto@synopsys.com>,
	"arnd@arndb.de" <arnd@arndb.de>,
	"wsa@the-dreams.de" <wsa@the-dreams.de>,
	"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	"bbrezillon@kernel.org" <bbrezillon@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"broonie@kernel.org" <broonie@kernel.org>,
	"linux-i3c@lists.infradead.org" <linux-i3c@lists.infradead.org>
Subject: Re: [PATCH v3 0/5] Introduce i3c device userspace interface
Date: Mon, 24 Feb 2020 12:24:42 +0100	[thread overview]
Message-ID: <20200224122442.7cb6e8d8@collabora.com> (raw)
In-Reply-To: <CH2PR12MB4216F86F6820CC5247B89BA8AEEC0@CH2PR12MB4216.namprd12.prod.outlook.com>

On Mon, 24 Feb 2020 10:53:25 +0000
Vitor Soares <Vitor.Soares@synopsys.com> wrote:

> Hi Boris,
> 
> From: Boris Brezillon <boris.brezillon@collabora.com>
> Date: Fri, Feb 21, 2020 at 17:41:16
> 
> > > > > 
> > > > > I want to make you know that none of your previous comments was ignored 
> > > > > and  I would like to start the discussion from this point.    
> > > > 
> > > > Sure, np. I'll probably wait for a v4 exploring the option I proposed
> > > > then.    
> > > 
> > > I would like to check with you:
> > >   - How can we prioritize the device driver over the i3cdev driver if the 
> > > driver is loaded after i3cdev? Currently, this is done automatically 
> > > without any command, and for me, this is a requirement.  
> > 
> > No devs would be bound to the i3cdev driver by default, it would have
> > to be done explicitly through a sysfs knob. Which makes me realize
> > we can't use the generic bind knob since it doesn't let the subsystem
> > know that it's a manual bind. I thought there was a way to distinguish
> > between manual and auto-bind.
> >   
> > >   - For the ioctl command structure, there is no rule about the way I did 
> > > or what you proposed, both are currently used in the kernel. For me it is 
> > > one more structure to deal with, can you point the advantages of your 
> > > purpose?  
> > 
> > I don't have a strong opinion on that one, though I find it a bit
> > easier to follow when the number of xfers is encoded in a separate
> > struct rather than extracted from the data size passed through the cmd
> > argument.  
> 
> I will change it then. Do you have any suggestion for the naming to keep 
> it short?

I named it i3cdev_priv_xfers in the patch I sent, but you can pick a
different name if you don't like this one.

> 
> >   
> > >   - Regarding the ioctl codes, I tried to use those after I2C.  
> > 
> > Why start from 0x30? It doesn't make sense to me. Just because you base
> > your code on something that already exists doesn't mean you have to
> > copy all of it.  
> 
> I might be wrong but last I2C command is 0x20 and I tried to let some 
> free space in case they need.
> Also I think that make sense I2C and I3C share the same 'magic number'.

Hm, I'm not sure that's a good idea. The set of ioctls for I2C and I3C
are likely to be completely different, so I'd recommend using a
separate namespace (AKA ioctl magic number). Wolfram, any opinion?

> 
> BTW, in ioctl-numbers documentation there is no reference for code 0x07.

Indeed, looks like it's not documented.

_______________________________________________
linux-i3c mailing list
linux-i3c@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-i3c