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Subject: Re: [RESEND PATCH v5 2/5] driver core: add deferring probe reason
 to devices_deferred property
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Jernej Skrabec <jernej.skrabec@siol.net>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        linux-kernel@vger.kernel.org,
        "open list:DRM DRIVERS" <dri-devel@lists.freedesktop.org>,
        Russell King - ARM Linux <linux@armlinux.org.uk>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Jonas Karlman <jonas@kwiboo.se>, andy.shevchenko@gmail.com,
        Mark Brown <broonie@kernel.org>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        linux-arm-kernel@lists.infradead.org,
        Marek Szyprowski <m.szyprowski@samsung.com>
From:   Andrzej Hajda <a.hajda@samsung.com>
Message-ID: <94ed179a-bcc7-1e52-985f-57e9c124a5f0@samsung.com>
Date:   Wed, 24 Jun 2020 15:26:15 +0200
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On 24.06.2020 14:34, Greg Kroah-Hartman wrote:
> On Wed, Jun 24, 2020 at 01:41:24PM +0200, Andrzej Hajda wrote:
>> /sys/kernel/debug/devices_deferred property contains list of deferred devices.
>> This list does not contain reason why the driver deferred probe, the patch
>> improves it.
>> The natural place to set the reason is probe_err function introduced recently,
>> ie. if probe_err will be called with -EPROBE_DEFER instead of printk the message
>> will be attached to deferred device and printed when user read devices_deferred
>> property.
>>
>> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
>> Reviewed-by: Mark Brown <broonie@kernel.org>
>> Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
>> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
>> ---
>>   drivers/base/base.h |  3 +++
>>   drivers/base/core.c | 10 ++++++----
>>   drivers/base/dd.c   | 21 ++++++++++++++++++++-
>>   3 files changed, 29 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/base/base.h b/drivers/base/base.h
>> index 95c22c0f9036..93ef1c2f4c1f 100644
>> --- a/drivers/base/base.h
>> +++ b/drivers/base/base.h
>> @@ -93,6 +93,7 @@ struct device_private {
>>   	struct klist_node knode_class;
>>   	struct list_head deferred_probe;
>>   	struct device_driver *async_driver;
>> +	char *deferred_probe_msg;
>>   	struct device *device;
>>   	u8 dead:1;
>>   };
>> @@ -134,6 +135,8 @@ extern void device_release_driver_internal(struct device *dev,
>>   extern void driver_detach(struct device_driver *drv);
>>   extern int driver_probe_device(struct device_driver *drv, struct device *dev);
>>   extern void driver_deferred_probe_del(struct device *dev);
>> +extern void __deferred_probe_set_msg(const struct device *dev,
>> +				     struct va_format *vaf);
>>   static inline int driver_match_device(struct device_driver *drv,
>>   				      struct device *dev)
>>   {
>> diff --git a/drivers/base/core.c b/drivers/base/core.c
>> index ee9da66bff1b..2a96954d5460 100644
>> --- a/drivers/base/core.c
>> +++ b/drivers/base/core.c
>> @@ -3962,6 +3962,8 @@ define_dev_printk_level(_dev_info, KERN_INFO);
>>    *
>>    * This helper implements common pattern present in probe functions for error
>>    * checking: print message if the error is not -EPROBE_DEFER and propagate it.
>> + * In case of -EPROBE_DEFER it sets defer probe reason, which can be checked
>> + * later by reading devices_deferred debugfs attribute.
>>    * It replaces code sequence:
>>    * 	if (err != -EPROBE_DEFER)
>>    * 		dev_err(dev, ...);
>> @@ -3977,14 +3979,14 @@ int probe_err(const struct device *dev, int err, const char *fmt, ...)
>>   	struct va_format vaf;
>>   	va_list args;
>>   
>> -	if (err == -EPROBE_DEFER)
>> -		return err;
>> -
>>   	va_start(args, fmt);
>>   	vaf.fmt = fmt;
>>   	vaf.va = &args;
>>   
>> -	dev_err(dev, "error %d: %pV", err, &vaf);
>> +	if (err == -EPROBE_DEFER)
>> +		__deferred_probe_set_msg(dev, &vaf);
>> +	else
>> +		dev_err(dev, "error %d: %pV", err, &vaf);
>>   
>>   	va_end(args);
>>   
>> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
>> index 9a1d940342ac..f44d26454b6a 100644
>> --- a/drivers/base/dd.c
>> +++ b/drivers/base/dd.c
>> @@ -27,6 +27,7 @@
>>   #include <linux/async.h>
>>   #include <linux/pm_runtime.h>
>>   #include <linux/pinctrl/devinfo.h>
>> +#include <linux/slab.h>
>>   
>>   #include "base.h"
>>   #include "power/power.h"
>> @@ -136,6 +137,8 @@ void driver_deferred_probe_del(struct device *dev)
>>   	if (!list_empty(&dev->p->deferred_probe)) {
>>   		dev_dbg(dev, "Removed from deferred list\n");
>>   		list_del_init(&dev->p->deferred_probe);
>> +		kfree(dev->p->deferred_probe_msg);
>> +		dev->p->deferred_probe_msg = NULL;
>>   	}
>>   	mutex_unlock(&deferred_probe_mutex);
>>   }
>> @@ -211,6 +214,21 @@ void device_unblock_probing(void)
>>   	driver_deferred_probe_trigger();
>>   }
>>   
>> +/*
>> + * __deferred_probe_set_msg() - Set defer probe reason message for device
>> + */
>> +void __deferred_probe_set_msg(const struct device *dev, struct va_format *vaf)
>> +{
>> +	const char *drv = dev_driver_string(dev);
>> +
>> +	mutex_lock(&deferred_probe_mutex);
>> +
>> +	kfree(dev->p->deferred_probe_msg);
>> +	dev->p->deferred_probe_msg = kasprintf(GFP_KERNEL, "%s: %pV", drv, vaf);
> What about the device name?  Don't you also want that?


deferred_devs_show prints it already, deferred_probe_msg is appended if 
not null.


Regards

Andrzej


>
> You want the same format that __dev_printk() outputs, please use that
> to be consistant with all other messages that drivers are spitting out.
>
> thanks,
>
> greg k-h
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