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

[Boris Brezillon]

On Tue, 19 Dec 2017 09:52:50 +0100
Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> 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 

> 
> Other than that, the driver core interaction looks good now, nice job.

Thanks.

Boris