Re: [PATCH v11 04/15] media: v4l2-fwnode: add initial connector parsing support

[Marco Felsch <m.felsch@pengutronix.de>]

Hi Sakari,

On 19-11-16 01:34, Sakari Ailus wrote:
> Hi Marco,
> 
> On Mon, Sep 30, 2019 at 11:38:49AM +0200, Marco Felsch wrote:
> > The patch adds the initial connector parsing code, so we can move from a
> > driver specific parsing code to a generic one. Currently only the
> > generic fields and the analog-connector specific fields are parsed. Parsing
> > the other connector specific fields can be added by a simple callbacks.
> > 
> > Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
> > ---
> > [1] https://patchwork.kernel.org/cover/10794703/
> > 
> > v10:
> > - drop V4L2_CONN_HDMI support
> > - adapt pr_err msg to reflect new state (-> connector is unkown)
> > 
> > v9:
> > - Fix leading semicolon found by kbuild semicolon.cocci
> > 
> > v8:
> > - V4L2_CON_* -> V4L2_CONN_*
> > - tvnorms -> sdtv-standards
> > - adapt to new v4l2_fwnode_connector_analog member
> > - return error in case of V4L2_CONN_HDMI
> > 
> > v7:
> > @Jacopo: I dropped your r b tag becuase of the amount of changes I
> > made..
> > 
> > - drop unnecessary comments
> > - fix commet style
> > - s/v4l2_fwnode_connector_conv.name/v4l2_fwnode_connector_conv.compatible/
> > - make label size variable and drop V4L2_CONNECTOR_MAX_LABEL usage
> > - do not assign a default label in case of no label was specified
> > - remove useless /* fall through */ comments
> > - add support for N connector links
> > - rename local variables to be more meaningful
> > - adjust kernedoc
> > - add v4l2_fwnode_connector_free()
> > - improve error handling (use different error values)
> > - make use of pr_warn_once()
> > 
> > v6:
> > - use unsigned count var
> > - fix comment and style issues
> > - place '/* fall through */' to correct places
> > - fix error handling and cleanup by releasing fwnode
> > - drop vga and dvi parsing support as those connectors are rarely used
> >   these days
> > 
> > v5:
> > - s/strlcpy/strscpy/
> > 
> > v2-v4:
> > - nothing since the patch was squashed from series [1] into this
> >   series.
> > ---
> >  drivers/media/v4l2-core/v4l2-fwnode.c | 129 ++++++++++++++++++++++++++
> >  include/media/v4l2-fwnode.h           |  38 ++++++++
> >  2 files changed, 167 insertions(+)
> > 
> > diff --git a/drivers/media/v4l2-core/v4l2-fwnode.c b/drivers/media/v4l2-core/v4l2-fwnode.c
> > index 3bd1888787eb..0bfa7cbf78df 100644
> > --- a/drivers/media/v4l2-core/v4l2-fwnode.c
> > +++ b/drivers/media/v4l2-core/v4l2-fwnode.c
> > @@ -595,6 +595,135 @@ void v4l2_fwnode_put_link(struct v4l2_fwnode_link *link)
> >  }
> >  EXPORT_SYMBOL_GPL(v4l2_fwnode_put_link);
> >  
> > +static const struct v4l2_fwnode_connector_conv {
> > +	enum v4l2_connector_type type;
> > +	const char *compatible;
> > +} connectors[] = {
> > +	{
> > +		.type = V4L2_CONN_COMPOSITE,
> > +		.compatible = "composite-video-connector",
> > +	}, {
> > +		.type = V4L2_CONN_SVIDEO,
> > +		.compatible = "svideo-connector",
> > +	},
> > +};
> > +
> > +static enum v4l2_connector_type
> > +v4l2_fwnode_string_to_connector_type(const char *con_str)
> > +{
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(connectors); i++)
> > +		if (!strcmp(con_str, connectors[i].compatible))
> > +			return connectors[i].type;
> > +
> > +	return V4L2_CONN_UNKNOWN;
> > +}
> > +
> > +static int
> > +v4l2_fwnode_connector_parse_analog(struct fwnode_handle *fwnode,
> > +				   struct v4l2_fwnode_connector *vc)
> > +{
> > +	u32 stds;
> > +	int ret;
> > +
> > +	ret = fwnode_property_read_u32(fwnode, "sdtv-standards", &stds);
> > +
> > +	/* The property is optional. */
> > +	vc->connector.analog.sdtv_stds = ret ? V4L2_STD_ALL : stds;
> > +
> > +	return 0;
> > +}
> > +
> > +void v4l2_fwnode_connector_free(struct v4l2_fwnode_connector *connector)
> > +{
> > +	unsigned int i;
> > +
> > +	if (IS_ERR_OR_NULL(connector))
> > +		return;
> > +
> > +	for (i = 0; i < connector->nr_of_links; i++)
> > +		v4l2_fwnode_put_link(&connector->links[i]);
> > +	kfree(connector->links);
> 
> Please do set connector->links NULL here. That avoids accidentally double
> kfree on the pointer.

Okay, I will do that.

> > +}
> > +EXPORT_SYMBOL_GPL(v4l2_fwnode_connector_free);
> > +
> > +int v4l2_fwnode_connector_alloc_parse(struct fwnode_handle *fwnode,
> > +				      struct v4l2_fwnode_connector *connector)
> > +{
> > +	struct fwnode_handle *remote_pp, *remote_ep;
> > +	const char *type_name;
> > +	unsigned int i = 0, ep_num = 0;
> > +	int err;
> > +
> > +	memset(connector, 0, sizeof(*connector));
> > +
> > +	remote_pp = fwnode_graph_get_remote_port_parent(fwnode);
> > +	if (!remote_pp)
> > +		return -ENOLINK;

Should I drop this logic here and force the caller to pass the connector
endpoint?

> > +
> > +	/* Parse all common properties first. */
> > +	fwnode_graph_for_each_endpoint(remote_pp, remote_ep)
> > +		ep_num++;
> 
> If there are no endpoints, ep_num will be zero and kmalloc_array() will
> return NULL? There should be a way there are no endpoints, rather than
> returning -ENOMEM.

Hm.. using the current implementation (please see my above comment)
ensures that there is always one link but if I change that I need to
check this, good point.

> > +
> > +	connector->nr_of_links = ep_num;
> > +	connector->links = kmalloc_array(ep_num, sizeof(*connector->links),
> > +					 GFP_KERNEL);
> > +	if (!connector->links) {
> > +		err = -ENOMEM;
> > +		goto err_put_fwnode;
> > +	}
> > +
> > +	fwnode_graph_for_each_endpoint(remote_pp, remote_ep) {
> > +		err = v4l2_fwnode_parse_link(remote_ep, &connector->links[i]);
> 
> If you start parsing a connector starting from another device connected to
> it, nothing seems to prevent parsing the same links twice, in case the
> connector is connected to more than one sub-device.
> 
> Or do I miss something crucial here?

That is true because currently each sub-device implements their own
connector parsing/handling stuff.. What i wanted to address with this
code is that one sub-device can have multiple links to one connector
e.g. s-video connectors (1xluma 1xchroma). I don't know how to handle
this without a simple connector device.

Regards,
  Marco

> > +		if (err) {
> > +			fwnode_handle_put(remote_ep);
> > +			goto err_free_links;
> > +		}
> > +		i++;
> > +	}
> > +
> > +	/*
> > +	 * Links reference counting guarantees access -> no duplication needed
> > +	 */
> > +	fwnode_property_read_string(remote_pp, "label", &connector->label);
> > +
> > +	/* The connector-type is stored within the compatible string. */
> > +	err = fwnode_property_read_string(remote_pp, "compatible", &type_name);
> > +	if (err) {
> > +		err = -EINVAL;
> > +		goto err_free_links;
> > +	}
> > +	connector->type = v4l2_fwnode_string_to_connector_type(type_name);
> > +
> > +	/* Now parse the connector specific properties. */
> > +	switch (connector->type) {
> > +	case V4L2_CONN_COMPOSITE:
> > +	case V4L2_CONN_SVIDEO:
> > +		err = v4l2_fwnode_connector_parse_analog(remote_pp, connector);
> > +		break;
> > +	case V4L2_CONN_UNKNOWN:
> > +	default:
> > +		pr_err("Unknown connector type\n");
> > +		err = -EINVAL;
> > +		goto err_free_links;
> > +	}
> > +
> > +	fwnode_handle_put(remote_pp);
> > +
> > +	return err;
> > +
> > +err_free_links:
> > +	for (i = 0; i < ep_num; i++)
> > +		v4l2_fwnode_put_link(&connector->links[i]);
> > +	kfree(connector->links);
> > +err_put_fwnode:
> > +	fwnode_handle_put(remote_pp);
> > +
> > +	return err;
> > +}
> > +EXPORT_SYMBOL_GPL(v4l2_fwnode_connector_alloc_parse);
> > +
> >  static int
> >  v4l2_async_notifier_fwnode_parse_endpoint(struct device *dev,
> >  					  struct v4l2_async_notifier *notifier,
> > diff --git a/include/media/v4l2-fwnode.h b/include/media/v4l2-fwnode.h
> > index 65da646b579e..800302aa84d8 100644
> > --- a/include/media/v4l2-fwnode.h
> > +++ b/include/media/v4l2-fwnode.h
> > @@ -276,6 +276,44 @@ int v4l2_fwnode_parse_link(struct fwnode_handle *fwnode,
> >   */
> >  void v4l2_fwnode_put_link(struct v4l2_fwnode_link *link);
> >  
> > +/**
> > + * v4l2_fwnode_connector_free() - free the V4L2 connector acquired by
> > + * v4l2_fwnode_parse_connector()
> 
> This would be nicer aligned with the text after the dash.
> 
> > + * @connector: the V4L2 connector the resources of which are to be released
> > + *
> > + * Drop references to the connection link partners and free the memory allocated
> > + * by v4l2_fwnode_parse_connector() call.
> > + *
> > + * It is safe to call this function with NULL argument or on a V4L2 connector
> > + * the parsing of which failed.
> > + */
> > +void v4l2_fwnode_connector_free(struct v4l2_fwnode_connector *connector);
> > +
> > +/**
> > + * v4l2_fwnode_parse_connector() - parse the connector on endpoint
> 
> The name is different from the actual function.
> 
> > + * @fwnode: pointer to the endpoint's fwnode handle where the connector is
> > + *          connected to
> > + * @connector: pointer to the V4L2 fwnode connector data structure
> > + *
> > + * Fill the connector data structure with the connector type, label, all found
> > + * links between the host and the connector as well as connector specific data.
> > + * Since the label is optional it can be %NULL if no one was found.
> > + *
> > + * A reference is taken to both the connector and the connector destination
> > + * where the connector belongs to. This must be dropped when no longer needed.
> > + * Also the memory it has allocated to store the variable size data must be
> > + * freed. Both dropping the references and freeing the memory is done by
> > + * v4l2_fwnode_connector_free().
> > + *
> > + * Return:
> > + * * %0 on success or a negative error code on failure:
> > + * * %-ENOMEM if memory allocation failed
> > + * * %-ENOLINK if the connector can't be found
> > + * * %-EINVAL on parsing failure
> 
> Could this error code tell the endpoint is not connected to a connector?
> 
> I think the perfectly suitable error code for this would be -ENOTCONN. :-D
> 
> > + */
> > +int v4l2_fwnode_connector_alloc_parse(struct fwnode_handle *fwnode,
> > +				      struct v4l2_fwnode_connector *connector);
> > +
> >  /**
> >   * typedef parse_endpoint_func - Driver's callback function to be called on
> >   *	each V4L2 fwnode endpoint.
> > 
> 
> -- 
> Regards,
> 
> Sakari Ailus
> sakari.ailus@linux.intel.com
> 

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