Re: [PATCH v6 1/4] driver core: add device probe log helper

[Sam Ravnborg]

Hi Andrzej

On Fri, Jun 26, 2020 at 12:01:00PM +0200, Andrzej Hajda wrote:
> During probe every time driver gets resource it should usually check for
> error printk some message if it is not -EPROBE_DEFER and return the error.
> This pattern is simple but requires adding few lines after any resource
> acquisition code, as a result it is often omitted or implemented only
> partially.
> dev_err_probe helps to replace such code sequences with simple call,
> so code:
> 	if (err != -EPROBE_DEFER)
> 		dev_err(dev, ...);
> 	return err;
> becomes:
> 	return probe_err(dev, err, ...);
s/probe_err/dev_err_probe/

	Sam
> 
> Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
> ---
>  drivers/base/core.c    | 42 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/device.h |  3 +++
>  2 files changed, 45 insertions(+)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 67d39a90b45c..3a827c82933f 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -3953,6 +3953,48 @@ define_dev_printk_level(_dev_info, KERN_INFO);
>  
>  #endif
>  
> +/**
> + * dev_err_probe - probe error check and log helper
> + * @dev: the pointer to the struct device
> + * @err: error value to test
> + * @fmt: printf-style format string
> + * @...: arguments as specified in the format string
> + *
> + * This helper implements common pattern present in probe functions for error
> + * checking: print debug or error message depending if the error value is
> + * -EPROBE_DEFER and propagate error upwards.
> + * It replaces code sequence:
> + * 	if (err != -EPROBE_DEFER)
> + * 		dev_err(dev, ...);
> + * 	else
> + * 		dev_dbg(dev, ...);
> + * 	return err;
> + * with
> + * 	return dev_err_probe(dev, err, ...);
> + *
> + * Returns @err.
> + *
> + */
> +int dev_err_probe(const struct device *dev, int err, const char *fmt, ...)
> +{
> +	struct va_format vaf;
> +	va_list args;
> +
> +	va_start(args, fmt);
> +	vaf.fmt = fmt;
> +	vaf.va = &args;
> +
> +	if (err != -EPROBE_DEFER)
> +		dev_err(dev, "error %d: %pV", err, &vaf);
> +	else
> +		dev_dbg(dev, "error %d: %pV", err, &vaf);
> +
> +	va_end(args);
> +
> +	return err;
> +}
> +EXPORT_SYMBOL_GPL(dev_err_probe);
> +
>  static inline bool fwnode_is_primary(struct fwnode_handle *fwnode)
>  {
>  	return fwnode && !IS_ERR(fwnode->secondary);
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 15460a5ac024..6b2272ae9af8 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -964,6 +964,9 @@ void device_link_remove(void *consumer, struct device *supplier);
>  void device_links_supplier_sync_state_pause(void);
>  void device_links_supplier_sync_state_resume(void);
>  
> +extern __printf(3, 4)
> +int dev_err_probe(const struct device *dev, int err, const char *fmt, ...);
> +
>  /* Create alias, so I can be autoloaded. */
>  #define MODULE_ALIAS_CHARDEV(major,minor) \
>  	MODULE_ALIAS("char-major-" __stringify(major) "-" __stringify(minor))
> -- 
> 2.17.1
> 
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