linux-kernel - Re: [PATCH v3 3/5] i3c: master: add i3c_for_each

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Message-ID: <20200221115229.GA116368@kroah.com>
Date:   Fri, 21 Feb 2020 12:52:29 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Vitor Soares <Vitor.Soares@...opsys.com>
Cc:     Jose Abreu <Jose.Abreu@...opsys.com>,
        "corbet@....net" <corbet@....net>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "wsa@...-dreams.de" <wsa@...-dreams.de>,
        "bbrezillon@...nel.org" <bbrezillon@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "linux-i3c@...ts.infradead.org" <linux-i3c@...ts.infradead.org>
Subject: Re: [PATCH v3 3/5] i3c: master: add i3c_for_each_dev helper

On Fri, Feb 21, 2020 at 11:47:22AM +0000, Vitor Soares wrote:
> Hi Greg,
> 
> From: Greg KH <gregkh@...uxfoundation.org>
> Date: Wed, Feb 19, 2020 at 07:35:48
> 
> > On Wed, Feb 19, 2020 at 01:20:41AM +0100, Vitor Soares wrote:
> > > Introduce i3c_for_each_dev(), an i3c device iterator for use by i3cdev.
> > > 
> > > Signed-off-by: Vitor Soares <vitor.soares@...opsys.com>
> > > ---
> > >  drivers/i3c/internals.h |  1 +
> > >  drivers/i3c/master.c    | 12 ++++++++++++
> > >  2 files changed, 13 insertions(+)
> > > 
> > > diff --git a/drivers/i3c/internals.h b/drivers/i3c/internals.h
> > > index bc062e8..a6deedf 100644
> > > --- a/drivers/i3c/internals.h
> > > +++ b/drivers/i3c/internals.h
> > > @@ -24,4 +24,5 @@ int i3c_dev_enable_ibi_locked(struct i3c_dev_desc *dev);
> > >  int i3c_dev_request_ibi_locked(struct i3c_dev_desc *dev,
> > >  			       const struct i3c_ibi_setup *req);
> > >  void i3c_dev_free_ibi_locked(struct i3c_dev_desc *dev);
> > > +int i3c_for_each_dev(void *data, int (*fn)(struct device *, void *));
> > >  #endif /* I3C_INTERNAL_H */
> > > diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> > > index 21c4372..8e22da2 100644
> > > --- a/drivers/i3c/master.c
> > > +++ b/drivers/i3c/master.c
> > > @@ -2640,6 +2640,18 @@ void i3c_dev_free_ibi_locked(struct i3c_dev_desc *dev)
> > >  	dev->ibi = NULL;
> > >  }
> > >  
> > > +int i3c_for_each_dev(void *data, int (*fn)(struct device *, void *))
> > > +{
> > > +	int res;
> > > +
> > > +	mutex_lock(&i3c_core_lock);
> > > +	res = bus_for_each_dev(&i3c_bus_type, NULL, data, fn);
> > > +	mutex_unlock(&i3c_core_lock);
> > 
> > Ick, why the lock?  Are you _sure_ you need that?  The core should
> > handle any list locking issues here, right?
> 
> I want to make sure that no new devices (eg: Hot-Join capable device) are 
> added during this iteration and after this call, each new device will 
> release a bus notification.
> 
> > 
> > I don't see bus-specific-locks around other subsystem functions that do
> > this (like usb_for_each_dev).
> 
> I based in I2C use case.

Check to see if this is really needed, for some reason I doubt it...

thanks,

greg k-h