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

From: Greg KH
Date: Fri Feb 21 2020 - 06:52:34 EST


On Fri, Feb 21, 2020 at 11:47:22AM +0000, Vitor Soares wrote:
> Hi Greg,
>
> From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
> 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@xxxxxxxxxxxx>
> > > ---
> > > 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