linux-kernel - RE: [RFC 5/5] i3c: add i3cdev module to expose i3c dev in /dev

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 12 Dec 2019 17:25:28 +0000
From:   Vitor Soares <Vitor.Soares@...opsys.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-i3c@...ts.infradead.org" <linux-i3c@...ts.infradead.org>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        "bbrezillon@...nel.org" <bbrezillon@...nel.org>,
        "wsa@...-dreams.de" <wsa@...-dreams.de>,
        "arnd@...db.de" <arnd@...db.de>,
        "broonie@...nel.org" <broonie@...nel.org>
Subject: RE: [RFC 5/5] i3c: add i3cdev module to expose i3c dev in /dev

From: Greg KH <gregkh@...uxfoundation.org>
Date: Thu, Dec 12, 2019 at 16:00:45

> On Thu, Dec 12, 2019 at 02:56:56PM +0000, Vitor Soares wrote:
> > Hi Greg,
> > 
> > From: Greg KH <gregkh@...uxfoundation.org>
> > Date: Thu, Dec 12, 2019 at 14:44:59
> > 
> > > On Tue, Dec 10, 2019 at 04:37:33PM +0100, Vitor Soares wrote:
> > > > +static int __init i3cdev_init(void)
> > > > +{
> > > > +	int res;
> > > > +
> > > > +	pr_info("i3c /dev entries driver\n");
> > > 
> > > Please remove debugging information, kernel code should be quiet unless
> > > something goes wrong.
> > 
> > I will remove it.
> > 
> > > 
> > > > +	/* Dynamically request unused major number */
> > > > +	res = alloc_chrdev_region(&i3cdev_number, 0, N_I3C_MINORS, "i3c");
> > > 
> > > Do you really need a whole major, or will a few minors work?
> > > 
> > > thanks,
> > > 
> > > greg k-h
> > 
> > I'm reserving one per device. What do you suggest?
> 
> How many devices do you have in a system?

According to MIPI I3C spec, the maximum number of devices on a bus will 
depend on trace length, bus load, and clock requirements.

Frankly, I don't know what is the best compromise because it depends from 
system to system and the end-use of it. In my case, I started developing 
this to help me during the HC controller driver development.
Even If I choose a fixed major, I wouldn't know in which one i3c fits.

Best regards,
Vitor Soares