linux-kernel - Re: [PATCH 2/4] i3c: master: Check if devices have i3c_dev_boardinfo on i3c_master_add_i3c_dev

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Message-ID: <20190829183721.33a4664d@collabora.com>
Date:   Thu, 29 Aug 2019 18:37:21 +0200
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Vitor Soares <Vitor.Soares@...opsys.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-i3c@...ts.infradead.org" <linux-i3c@...ts.infradead.org>,
        "bbrezillon@...nel.org" <bbrezillon@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>
Subject: Re: [PATCH 2/4] i3c: master: Check if devices have
 i3c_dev_boardinfo on i3c_master_add_i3c_dev_locked()

On Thu, 29 Aug 2019 16:33:43 +0000
Vitor Soares <Vitor.Soares@...opsys.com> wrote:

> From: Boris Brezillon <boris.brezillon@...labora.com>
> Date: Thu, Aug 29, 2019 at 17:15:20
> 
> > On Thu, 29 Aug 2019 15:57:32 +0000
> > Vitor Soares <Vitor.Soares@...opsys.com> wrote:
> >   
> > > -----Original Message-----
> > > From: Boris Brezillon 
> > > <boris.brezillon@...labora.com> 
> > > Sent: Thursday, August 29, 2019 4:25 
> > > PM
> > > To: Vitor Soares <Vitor.Soares@...opsys.com>
> > > Cc: 
> > > linux-kernel@...r.kernel.org; devicetree@...r.kernel.org; 
> > > linux-i3c@...ts.infradead.org; bbrezillon@...nel.org; robh+dt@...nel.org; 
> > > mark.rutland@....com; Joao.Pinto@...opsys.com
> > > Subject: Re: [PATCH 2/4] 
> > > i3c: master: Check if devices have i3c_dev_boardinfo on 
> > > i3c_master_add_i3c_dev_locked()
> > > 
> > > On Thu, 29 Aug 2019 15:07:08 +0000
> > > Vitor Soares <Vitor.Soares@...opsys.com> wrote:
> > >   
> > > > From: Boris Brezillon     
> > > <boris.brezillon@...labora.com>  
> > > > Date: Thu, Aug 29, 2019 at 15:39:41
> > > >     
> > >   
> > > > > On Thu, 29 Aug 2019 16:39:18 +0200
> > > > > Boris Brezillon <boris.brezillon@...labora.com> wrote:
> > > > >       
> > > > > > On Thu, 29 Aug 2019 14:00:44 +0000
> > > > > > Vitor Soares <Vitor.Soares@...opsys.com> wrote:
> > > > > >       
> > > > > > > Hi Boris,
> > > > > > > 
> > > > > > > From: Boris Brezillon <boris.brezillon@...labora.com>
> > > > > > > Date: Thu, Aug 29, 2019 at 11:44:57
> > > > > > >         
> > > > > > > > On Thu, 29 Aug 2019 12:19:33 +0200
> > > > > > > > Vitor Soares <Vitor.Soares@...opsys.com> wrote:
> > > > > > > >           
> > > > > > > > > The I3C devices described in DT might not be attached to the master which
> > > > > > > > > doesn't allow to assign a specific dynamic address.          
> > > > > > > > 
> > > > > > > > I remember testing this when developing the framework, so, unless
> > > > > > > > another patch regressed it, it should already work. I suspect patch 1
> > > > > > > > is actually the regressing this use case.          
> > > > > > > 
> > > > > > > For today it doesn't address the case where the device is described with 
> > > > > > > static address = 0, which isn't attached to the controller.        
> > > > > > 
> > > > > > Hm, I'm pretty sure I had designed the code to support that case (see
> > > > > > [1]). It might be buggy, but nothing we can't fix I guess.
> > > > > >       
> > > > > 
> > > > > [1]https://urldefense.proofpoint.com/v2/url?u=https-3A__elixir.bootlin.com_linux_v5.3-2Drc6_source_drivers_i3c_master.c-23L1898&d=DwICAg&c=DPL6_X_6JkXFx7AXWqB0tg&r=qVuU64u9x77Y0Kd0PhDK_lpxFgg6PK9PateHwjb_DY0&m=IXS1ygIgEo5vwajk0iwd5aBDVBzRnVTjO3cg4iBmGNc&s=HC-AcYm-AZPrUBoALioej_BDnqOtJHltr39Z2yPkuU4&e=       
> > > > 
> > > > That is only valid if you have olddev which will only exist if static 
> > > > address != 0.    
> > > 
> > > Hm, if you revert patch 1 (and assuming the device is properly defined
> > > in the DT), you should have olddev != NULL when reaching that point. If
> > > that's not the case there's a bug somewhere that should be fixed.
> > > 
> > > No, because the device is not attached.  
> > 
> > Oh, my bad, I see what you mean now. This is definitely a bug and should
> > have the Fixes tags. I mean, even if we don't care about dynamic
> > address assignment, I3C drivers might care about the ->of_node that's
> > attached to the device.  
> 
> I didn't consider a bug because in dt-bindings says to not use 'assigned 
> address' if SA = 0.

The fact that we don't try to assign a predefined dynamic address
when !SA is indeed not a bug, but failing to propagate the ->of_node
info to the i3c_device is one.

> Do you think there is a better way to solve it?

Your patch is correct, I just proposed a few adjustments.