Date:   Tue, 28 Dec 2021 09:04:01 -0800
From:   Bjorn Andersson <bjorn.andersson@linaro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc:     Kishon Vijay Abraham I <kishon@ti.com>,
        Vinod Koul <vkoul@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Hans de Goede <hdegoede@redhat.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        linux-arm-msm@vger.kernel.org, linux-phy@lists.infradead.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-usb@vger.kernel.org
Subject: Re: [PATCH 3/8] device property: Helper to match multiple connections
Message-ID: <YctDgaHV8dsR109L@ripper>
References: <20211228052116.1748443-1-bjorn.andersson@linaro.org>
 <20211228052116.1748443-4-bjorn.andersson@linaro.org>
 <78491489-6b31-c741-8c69-8d52fb614a6c@linaro.org>
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In-Reply-To: <78491489-6b31-c741-8c69-8d52fb614a6c@linaro.org>
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On Tue 28 Dec 05:09 PST 2021, Dmitry Baryshkov wrote:

> On 28/12/2021 08:21, Bjorn Andersson wrote:
> > In some cases multiple connections with the same connection id
> > needs to be resolved from a fwnode graph.
> > 
> > One such example is when separate hardware is used for performing muxing and/or
> > orientation switching of the SuperSpeed and SBU lines in a USB-C
> > connector. In this case the connector needs to belong to a graph with
> > multiple matching remote endpoints, and the TypeC controller needs to be
> > able to resolve them both.
> > 
> > Add a new API that allows this kind of lookup.
> > 
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> > ---
> >   drivers/base/property.c  | 94 ++++++++++++++++++++++++++++++++++++++++
> >   include/linux/property.h |  5 +++
> >   2 files changed, 99 insertions(+)
> > 
> > diff --git a/drivers/base/property.c b/drivers/base/property.c
> > index cbe4fa298413..0aa0296fd991 100644
> > --- a/drivers/base/property.c
> > +++ b/drivers/base/property.c
> > @@ -1180,6 +1180,36 @@ fwnode_graph_devcon_match(struct fwnode_handle *fwnode, const char *con_id,
> >   	return NULL;
> >   }
> > +static unsigned int fwnode_graph_devcon_matches(struct fwnode_handle *fwnode,
> > +						const char *con_id, void *data,
> > +						devcon_match_fn_t match,
> > +						void **matches,
> > +						unsigned int matches_len)
> > +{
> > +	struct fwnode_handle *node;
> > +	struct fwnode_handle *ep;
> > +	unsigned int count = 0;
> > +	void *ret;
> > +
> > +	fwnode_graph_for_each_endpoint(fwnode, ep) {
> > +		if (count >= matches_len) {
> > +			fwnode_handle_put(ep);
> > +			return count;
> > +		}
> > +
> > +		node = fwnode_graph_get_remote_port_parent(ep);
> > +		if (!fwnode_device_is_available(node))
> > +			continue;
> > +
> > +		ret = match(node, con_id, data);
> > +		fwnode_handle_put(node);
> > +
> > +		if (ret)
> > +			matches[count++] = ret;
> > +	}
> > +	return count;
> > +}
> 
> This API doesn't let it's user know if there are more matches found in the
> device tree or not. I'd suggest to add 'count' mode that would return the
> amount of found matches if (matches == NULL) && (matches_len == 0).
> 

Unfortunately in this code path we don't know how to "free" the objects
returned by match(), e.g. see how typec_switch_match() returns wrapper
of a refcounted device.

So we must return all the match results to the caller to it can free
things up based on its knowledge of what matches[] actually contains..

Regards,
Bjorn

> > +
> >   static void *
> >   fwnode_devcon_match(struct fwnode_handle *fwnode, const char *con_id,
> >   		    void *data, devcon_match_fn_t match)
> > @@ -1202,6 +1232,35 @@ fwnode_devcon_match(struct fwnode_handle *fwnode, const char *con_id,
> >   	return NULL;
> >   }
> > +static unsigned int fwnode_devcon_matches(struct fwnode_handle *fwnode,
> > +					  const char *con_id, void *data,
> > +					  devcon_match_fn_t match,
> > +					  void **matches,
> > +					  unsigned int matches_len)
> > +{
> > +	struct fwnode_handle *node;
> > +	unsigned int count = 0;
> > +	void *ret;
> > +	int i;
> > +
> > +	for (i = 0; ; i++) {
> > +		if (count >= matches_len)
> > +			return count;
> > +
> > +		node = fwnode_find_reference(fwnode, con_id, i);
> > +		if (IS_ERR(node))
> > +			break;
> > +
> > +		ret = match(node, NULL, data);
> > +		fwnode_handle_put(node);
> > +
> > +		if (ret)
> > +			matches[count++] = ret;
> > +	}
> > +
> > +	return count;
> > +}
> > +
> 
> Same comment applies.
> 
> >   /**
> >    * fwnode_connection_find_match - Find connection from a device node
> >    * @fwnode: Device node with the connection
> > @@ -1229,3 +1288,38 @@ void *fwnode_connection_find_match(struct fwnode_handle *fwnode,
> >   	return fwnode_devcon_match(fwnode, con_id, data, match);
> >   }
> >   EXPORT_SYMBOL_GPL(fwnode_connection_find_match);
> > +
> > +/**
> > + * fwnode_connection_find_matches - Find connections from a device node
> > + * @fwnode: Device node with the connection
> > + * @con_id: Identifier for the connection
> > + * @data: Data for the match function
> > + * @match: Function to check and convert the connection description
> > + * @matches: Array of pointers to fill with matches
> > + * @matches_len: Length of @matches
> > + *
> > + * Find up to @matches_len connections with unique identifier @con_id between
> > + * @fwnode and other device nodes. @match will be used to convert the
> > + * connection description to data the caller is expecting to be returned
> > + * through the @matches array.
> > + *
> > + * Return: Number of matches resolved, of negative errno.
> > + */
> > +int fwnode_connection_find_matches(struct fwnode_handle *fwnode,
> > +				   const char *con_id, void *data,
> > +				   devcon_match_fn_t match,
> > +				   void **matches, unsigned int matches_len)
> > +{
> > +	unsigned int count;
> > +
> > +	if (!fwnode || !match || !matches)
> > +		return -EINVAL;
> > +
> > +	count = fwnode_graph_devcon_matches(fwnode, con_id, data, match,
> > +					    matches, matches_len);
> > +
> > +	return count + fwnode_devcon_matches(fwnode, con_id, data, match,
> > +					     matches + count,
> > +					     matches_len - count);
> > +}
> > +EXPORT_SYMBOL_GPL(fwnode_connection_find_matches);
> > diff --git a/include/linux/property.h b/include/linux/property.h
> > index 16f736c698a2..59484ccb260e 100644
> > --- a/include/linux/property.h
> > +++ b/include/linux/property.h
> > @@ -444,6 +444,11 @@ static inline void *device_connection_find_match(struct device *dev,
> >   	return fwnode_connection_find_match(dev_fwnode(dev), con_id, data, match);
> >   }
> > +int fwnode_connection_find_matches(struct fwnode_handle *fwnode,
> > +				   const char *con_id, void *data,
> > +				   devcon_match_fn_t match,
> > +				   void **matches, unsigned int matches_len);
> > +
> >   /* -------------------------------------------------------------------------- */
> >   /* Software fwnode support - when HW description is incomplete or missing */
> 
> 
> -- 
> With best wishes
> Dmitry