linux-kernel - Re: [RESEND PATCH v3 02/17] media: v4l2-fwnode: Pass notifier to v4l2_async_register_fwnode

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Message-ID: <c9b232d6-07c9-d13d-18aa-3e1e640aadc2@gmail.com>
Date:   Fri, 28 Feb 2020 10:16:06 -0800
From:   Steve Longerbeam <slongerbeam@...il.com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     linux-media@...r.kernel.org,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Rui Miguel Silva <rmfrfs@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:STAGING SUBSYSTEM" <devel@...verdev.osuosl.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RESEND PATCH v3 02/17] media: v4l2-fwnode: Pass notifier to
 v4l2_async_register_fwnode_subdev()

Hi Sakari,

On 2/25/20 7:07 AM, Sakari Ailus wrote:
> Hi Steve,
>
> On Sat, Feb 15, 2020 at 11:41:21AM -0800, Steve Longerbeam wrote:
>> Instead of allocating a notifier in v4l2_async_register_fwnode_subdev(),
>> have the caller provide one. This allows the caller to implement
>> notifier ops (bind, unbind).
>>
>> The caller is now responsible for first initializing its notifier with a
>> call to v4l2_async_notifier_init().
>>
>> Signed-off-by: Steve Longerbeam <slongerbeam@...il.com>
> Instead of improving v4l2_async_register_fwnode_subdev(), could you convert
> the users (IMX driver in this case) to call the preferred APIs instead? As
> the lines below show, v4l2_async_register_fwnode_subdev() has only two
> users left --- the other one of which is the IMX driver. After converting
> these two, we could just remove this API.
>
> See e.g. drivers/media/pci/intel/ipu3/ipu3-cio2.c and
> drivers/media/platform/omap3isp/isp.c for examples.

Shouldn't v4l2_async_notifier_add_fwnode_remote_subdev() check for the 
availability of the remote before adding it to the notifier's asd list, 
as in:

diff --git a/drivers/media/v4l2-core/v4l2-async.c 
b/drivers/media/v4l2-core/v4l2-async.c
index 8bde33c21ce4..b48ed68c6c6c 100644
--- a/drivers/media/v4l2-core/v4l2-async.c
+++ b/drivers/media/v4l2-core/v4l2-async.c
@@ -615,7 +615,7 @@ v4l2_async_notifier_add_fwnode_remote_subdev(struct 
v4l2_async_notifier *notif,
         int ret;

         remote = fwnode_graph_get_remote_port_parent(endpoint);
-       if (!remote)
+       if (!remote || !fwnode_device_is_available(remote))
                 return -ENOTCONN;

         asd->match_type = V4L2_ASYNC_MATCH_FWNODE;


Otherwise we are back to the problem that the notifier will never 
complete because the remote's driver is not probed.

Steve

>
>> ---
>> Changes in v3:
>> - added the missing calls to unregister/cleanup the new subdev notifiers.
>>    Reported by Rui Silva.
>> ---
>>   drivers/media/platform/video-mux.c         |  8 +++++++-
>>   drivers/media/v4l2-core/v4l2-fwnode.c      | 11 +----------
>>   drivers/staging/media/imx/imx6-mipi-csi2.c |  7 ++++++-
>>   drivers/staging/media/imx/imx7-media-csi.c |  7 ++++++-
>>   drivers/staging/media/imx/imx7-mipi-csis.c |  9 ++++++++-
>>   include/media/v4l2-fwnode.h                | 12 ++++++++----
>>   6 files changed, 36 insertions(+), 18 deletions(-)