RE: [PATCH v3 3/5] i3c: master: add i3c_for_each_dev helper

[Vitor Soares <Vitor.Soares@synopsys.com>]

Hi Greg,

From: Greg KH <gregkh@linuxfoundation.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@synopsys.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.

> 
> thanks,
> 
> greg k-h
> 
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Best regards,
Vitor Soares

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