Re: [PATCH v2 2/7] i3c: Add core I3C infrastructure

Greg Kroah-Hartman
2017-12-19T09:21:19Z

On Tue, Dec 19, 2017 at 10:13:36AM +0100, Boris Brezillon wrote:
> On Tue, 19 Dec 2017 10:09:00 +0100
> Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org> wrote:
>
> > On Tue, 19 Dec 2017 09:52:50 +0100
> > Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org> wrote:
> >
> > > On Thu, Dec 14, 2017 at 04:16:05PM +0100, Boris Brezillon wrote:
> > > > +/**
> > > > + * i3c_device_match_id() - Find the I3C device ID entry matching an I3C dev
> > > > + * @i3cdev: the I3C device we're searching a match for
> > > > + * @id_table: the I3C device ID table
> > > > + *
> > > > + * Return: a pointer to the first entry matching @i3cdev, or NULL if there's
> > > > + * no match.
> > > > + */
> > > > +const struct i3c_device_id *
> > > > +i3c_device_match_id(struct i3c_device *i3cdev,
> > > > + const struct i3c_device_id *id_table)
> > > > +{
> > > > + const struct i3c_device_id *id;
> > > > +
> > > > + /*
> > > > + * The lower 32bits of the provisional ID is just filled with a random
> > > > + * value, try to match using DCR info.
> > > > + */
> > > > + if (!I3C_PID_RND_LOWER_32BITS(i3cdev->info.pid)) {
> > > > + u16 manuf = I3C_PID_MANUF_ID(i3cdev->info.pid);
> > > > + u16 part = I3C_PID_PART_ID(i3cdev->info.pid);
> > > > + u16 ext_info = I3C_PID_EXTRA_INFO(i3cdev->info.pid);
> > > > +
> > > > + /* First try to match by manufacturer/part ID. */
> > > > + for (id = id_table; id->match_flags != 0; id++) {
> > > > + if ((id->match_flags & I3C_MATCH_MANUF_AND_PART) !=
> > > > + I3C_MATCH_MANUF_AND_PART)
> > > > + continue;
> > > > +
> > > > + if (manuf != id->manuf_id || part != id->part_id)
> > > > + continue;
> > > > +
> > > > + if ((id->match_flags & I3C_MATCH_EXTRA_INFO) &&
> > > > + ext_info != id->extra_info)
> > > > + continue;
> > > > +
> > > > + return id;
> > > > + }
> > > > + }
> > > > +
> > > > + /* Fallback to DCR match. */
> > > > + for (id = id_table; id->match_flags != 0; id++) {
> > > > + if ((id->match_flags & I3C_MATCH_DCR) &&
> > > > + id->dcr == i3cdev->info.dcr)
> > > > + return id;
> > > > + }
> > > > +
> > > > + return NULL;
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(i3c_device_match_id);
> > >
> > > I just picked one random export here, but it feels like you are
> > > exporting a bunch of symbols you don't need to. Why would something
> > > outside of the i3c "core" need to call this function?
> >
> > Because I'm not passing the i3c_device_id to the ->probe() method, and
> > if the driver is supporting different variants of the device, it may
> > want to know which one is being probed.
> >
> > I considered retrieving this information in the core just before probing
> > the driver and passing it to the ->probe() function, but it means
> > having an extra i3c_device_match_id() call for everyone even those who
> > don't care about the device_id information, so I thought exporting this
> > function was a good alternative (device drivers can use it when they
> > actually need to retrieve the device_id).
> >
> > Anyway, that's something I can change if you think passing the
> > i3c_device_id to the ->probe() method is preferable.
> >
> > > Have you looked
> > > to see if you really have callers for everything you are exporting?
> >
> > Yes, I tried to only export functions that I think will be needed by
> > I3C device drivers and I3C master drivers. Note that I didn't post the
> > dummy device driver I developed to test the framework (partly because
> > this is
>
> Sorry, I hit the send button before finishing my sentence :-).
>
> "
> Note that I didn't post the dummy device driver [1] I developed to test
> the framework (partly because the quality of the code does not meet
> mainline standards and I was ashamed of posting it publicly :-)), but
> this driver is using some of the exported functions.
> "

We don't export functions that has no in-kernel users :)

thanks,

greg k-h
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