On 10/16/2018 09:22 AM, 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.ha...@samsung.com>
> ---
>  drivers/base/base.h |  3 +++
>  drivers/base/core.c | 15 +++++++++------
>  drivers/base/dd.c   | 34 +++++++++++++++++++++++++++++++++-
>  3 files changed, 45 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/base/base.h b/drivers/base/base.h
> index 7a419a7a6235..6f9371bfe40b 100644
> --- a/drivers/base/base.h
> +++ b/drivers/base/base.h
> @@ -75,6 +75,7 @@ struct device_private {
>       struct klist_node knode_driver;
>       struct klist_node knode_bus;
>       struct list_head deferred_probe;
> +     char *deferred_probe_msg;
>       struct device *device;
>  };
>  #define to_device_private_parent(obj)        \
> @@ -113,6 +114,8 @@ 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, const char 
> *fmt,
> +                                  va_list args);
>  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 23fabefb217a..df9895adf11b 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -3076,6 +3076,7 @@ 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.
>   * It replaces code sequence:
>   *   if (err != -EPROBE_DEFER)
>   *           dev_err(dev, ...);
> @@ -3091,15 +3092,17 @@ int probe_err(const struct device *dev, int err, 
> const char *fmt, ...)
>       struct va_format vaf;
>       va_list args;
>  
> -     if (err != -EPROBE_DEFER) {
> -             va_start(args, fmt);
> +     va_start(args, fmt);
>  
> -             vaf.fmt = fmt;
> -             vaf.va = &args;
> +     vaf.fmt = fmt;
> +     vaf.va = &args;
>  
> +     if (err != -EPROBE_DEFER)
>               __dev_printk(KERN_ERR, dev, &vaf);
> -             va_end(args);
> -     }
> +     else
> +             __deferred_probe_set_msg(dev, fmt, args);
> +
> +     va_end(args);
>  
>       return err;
>  }
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 169412ee4ae8..e2f81e538d4b 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"
> @@ -132,6 +133,8 @@ 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);
>  }
> @@ -202,6 +205,32 @@ 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, const char *fmt,
> +                                  va_list args)
> +{
> +     const int size = 128;
> +     char **p;
> +     int n;
> +
> +     mutex_lock(&deferred_probe_mutex);
> +
> +     p = &dev->p->deferred_probe_msg;
> +     if (!*p) {
> +             *p = kmalloc(size, GFP_KERNEL);
> +             if (!*p)
> +                     goto end;
> +     }
> +     n = snprintf(*p, size, "%s %s: ", dev_driver_string(dev), 
> dev_name(dev));
> +     if (n < size)
> +             vsnprintf(*p + n, size - n, fmt, args);

I wonder if the vsnprintf() return value should be checked and print a warning
if the message was truncated. Probably 128 is enough for most error messages?

Reviewed-by: Javier Martinez Canillas <javi...@redhat.com>
 
Best regards,
-- 
Javier Martinez Canillas
Software Engineer - Desktop Hardware Enablement
Red Hat

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