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SubjectRe: [PATCH 2/3] driver core: add deferring probe reason to devices_deferred property
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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.hajda@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 <javierm@redhat.com>

Best regards,
--
Javier Martinez Canillas
Software Engineer - Desktop Hardware Enablement
Red Hat

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