linux-kernel - Re: [RFC PATCH v3 7/9] ipu3-cio2: Check if pci_dev->dev's fwnode is a software_node in cio2_parse_firmware() and set FWNODE_GRAPH_DEVICE

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Message-ID: <20201024003955.GS5979@pendragon.ideasonboard.com>
Date:   Sat, 24 Oct 2020 03:39:55 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     Dan Scally <djrscally@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux.walleij@...aro.org, prabhakar.mahadev-lad.rj@...renesas.com,
        heikki.krogerus@...ux.intel.com, dmitry.torokhov@...il.com,
        laurent.pinchart+renesas@...asonboard.com,
        kieran.bingham+renesas@...asonboard.com, jacopo+renesas@...ndi.org,
        robh@...nel.org, davem@...emloft.net, linux@...musvillemoes.dk,
        sergey.senozhatsky@...il.com, rostedt@...dmis.org,
        pmladek@...e.com, mchehab@...nel.org, tian.shu.qiu@...el.com,
        bingbu.cao@...el.com, yong.zhi@...el.com, rafael@...nel.org,
        gregkh@...uxfoundation.org, kitakar@...il.com,
        dan.carpenter@...cle.org
Subject: Re: [RFC PATCH v3 7/9] ipu3-cio2: Check if pci_dev->dev's fwnode is
 a software_node in cio2_parse_firmware() and set
 FWNODE_GRAPH_DEVICE_DISABLED if so

Hi Sakari

On Wed, Oct 21, 2020 at 01:49:10AM +0300, Sakari Ailus wrote:
> On Tue, Oct 20, 2020 at 08:56:07PM +0100, Dan Scally wrote:
> > On 20/10/2020 13:06, Sakari Ailus wrote:
> > > On Tue, Oct 20, 2020 at 12:19:58PM +0300, Andy Shevchenko wrote:
> > >> On Mon, Oct 19, 2020 at 11:59:01PM +0100, Daniel Scally wrote:
> > >>> fwnode_graph_get_endpoint_by_id() will optionally parse enabled devices
> > >>> only; that status being determined through the .device_is_available() op
> > >>> of the device's fwnode. As software_nodes don't have that operation and
> > >>> adding it is meaningless, we instead need to check if the device's fwnode
> > >>> is a software_node and if so pass the appropriate flag to disable that
> > >>> check
> > >> Period.
> > >>
> > >> I'm wondering if actually this can be hidden in fwnode_graph_get_endpoint_by_id().
> > > The device availability test is actually there for a reason. Some firmware
> > > implementations put all the potential devices in the tables and only one
> > > (of some) of them are available.
> > >
> > > Could this be implemented so that if the node is a software node, then get
> > > its parent and then see if that is available?
> > >
> > > I guess that could be implemented in software node ops. Any opinions?
> > Actually when considering the cio2 device, it seems that
> > set_secondary_fwnode() actually overwrites the _primary_, given
> > fwnode_is_primary(dev->fwnode) returns false. So in at least some cases,
> > this wouldn't work.
> 
> Ouch. I wonder when this happens --- have you checked what's the primary
> there? I guess it might be if it's a PCI device without the corresponding
> ACPI device node?
> 
> I remember you had an is_available implementation that just returned true
> for software nodes in an early version of the set? I think it would still
> be a lesser bad in this case.

How about the following ?

diff --git a/drivers/base/property.c b/drivers/base/property.c
index 81bd01ed4042..ea44ba846299 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -706,9 +706,14 @@ EXPORT_SYMBOL_GPL(fwnode_handle_put);
 /**
  * fwnode_device_is_available - check if a device is available for use
  * @fwnode: Pointer to the fwnode of the device.
+ *
+ * For fwnode node types that don't implement the .device_is_available()
+ * operation, such as software nodes, this function returns true.
  */
 bool fwnode_device_is_available(const struct fwnode_handle *fwnode)
 {
+	if (!fwnode_has_op(fwnode, device_is_available))
+		return true;
 	return fwnode_call_bool_op(fwnode, device_is_available);
 }
 EXPORT_SYMBOL_GPL(fwnode_device_is_available);

-- 
Regards,

Laurent Pinchart