Hi Heikki,
> From: Heikki Krogerus, Sent: Monday, May 14, 2018 10:28 PM
>
> On Mon, May 14, 2018 at 06:15:57PM +0900, Yoshihiro Shimoda wrote:
<snip>
> > diff --git a/drivers/base/devcon.c b/drivers/base/devcon.c
> > index d427e80..5a0da33 100644
> > --- a/drivers/base/devcon.c
> > +++ b/drivers/base/devcon.c
<snip>
> > +static int generic_graph_match(struct device *dev, void *fwnode)
> > +{
> > + return dev->fwnode == fwnode;
> > +}
> > +
> > +/**
> > + * device_connection_find_by_graph - Find two devices connected together
> > + * @dev: Device to find connected device
> > + * @port: identifier of the @dev port node
> > + * @endpoint: identifier of the @dev endpoint node
> > + *
> > + * Find a connection with @port and @endpoint by using graph between @dev and
> > + * another device. On success returns handle to the device that is connected
> > + * to @dev, with the reference count for the found device incremented. Returns
> > + * NULL if no matching connection was found, or ERR_PTR(-EPROBE_DEFER) when
> > + * a connection was found but the other device has not been enumerated yet.
> > + */
> > +struct device *device_connection_find_by_graph(struct device *dev, u32 port,
> > + u32 endpoint)
> > +{
> > + struct bus_type *bus;
> > + struct fwnode_handle *remote;
> > + struct device *conn;
> > +
> > + remote = fwnode_graph_get_remote_node(dev_fwnode(dev), port, endpoint);
> > + if (!remote)
> > + return NULL;
> > +
> > + for (bus = generic_match_buses[0]; bus; bus++) {
> > + conn = bus_find_device(bus, NULL, remote, generic_graph_match);
> > + if (conn)
> > + return conn;
> > + }
> > +
> > + /*
> > + * We only get called if a connection was found, tell the caller to
> > + * wait for the other device to show up.
> > + */
> > + return ERR_PTR(-EPROBE_DEFER);
> > +}
> > +EXPORT_SYMBOL_GPL(device_connection_find_by_graph);
>
> Why do we need more API for walking through the graph?
I thought there is difficult to find if a device has multiple ports or endpoints.
So, I'd like to use port and endpoint number for finding a device.
> I'm not sure exactly sure what is going on here, I'll try to study
> your patches more when I have time, but the approach looks wrong. That
> function looks like a helper, but just not that useful one.
>
> We really should be able to use the existing functions. In practice
> device_connection_find_match() should eventually parse the graph, then
> fallback to build-in connections if no graph is found. Otherwise
> parsing graph here is not really useful at all.
I think using device_connection_find_match() for finding the graph becomes complicated.
The current arguments of the function is the below:
void *device_connection_find_match(struct device *dev, const char *con_id,
void *data,
void *(*match)(struct device_connection *con,
int ep, void *data))
If finding the graph, the following arguments will be not used.
- con_id
- *con and ep of "match" arguments.
This is because these arguments are for the build-in connections.
So, should I modify the arguments of the function for finding both
the graph and built-in connections somehow?
Best regards,
Yoshihiro Shimoda
>
> Thanks,
>
> --
> heikki
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