linux-kernel - Re: [PATCH v4 1/3] driver core: add probe

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Message-ID: <CAJZ5v0in=0FVaoUeL=s8CS+pGVpVo460sTXg4MX_P17pss7JbA@mail.gmail.com>
Date:   Thu, 20 Dec 2018 11:35:26 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Andrzej Hajda <a.hajda@...sung.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        javierm@...hat.com,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>
Subject: Re: [PATCH v4 1/3] driver core: add probe_err log helper

On Thu, Dec 20, 2018 at 11:23 AM Andrzej Hajda <a.hajda@...sung.com> 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 omited or implemented only partially.
> probe_err 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, ...);
>
> Signed-off-by: Andrzej Hajda <a.hajda@...sung.com>
> Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>
> Reviewed-by: Mark Brown <broonie@...nel.org>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

I'm not entirely convinced that the dev_err() log level is adequate
for this purpose, but anyway it looks like this may reduce code
duplication quite a bit, so

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

> ---
> v3:
>   - added 'extern __printf(3, 4)' decorators to probe_err,
>   - changed error logging format - newline at the end,
>   - added empty lines in probe_err around dev_err,
>   - added R-b by Mark and Andy.
> v2:
>   - added error value to log message,
>   - fixed code style,
>   - added EXPORT_SYMBOL_GPL,
>   - Added R-B by Javier (I hope the changes did not invalidate it).
> ---
>  drivers/base/core.c    | 39 +++++++++++++++++++++++++++++++++++++++
>  include/linux/device.h |  3 +++
>  2 files changed, 42 insertions(+)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 0073b09bb99f..7f644f3c41d3 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -3099,6 +3099,45 @@ define_dev_printk_level(_dev_info, KERN_INFO);
>
>  #endif
>
> +/**
> + * probe_err - 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 message if the error is not -EPROBE_DEFER and propagate it.
> + * It replaces code sequence:
> + *     if (err != -EPROBE_DEFER)
> + *             dev_err(dev, ...);
> + *     return err;
> + * with
> + *     return probe_err(dev, err, ...);
> + *
> + * Returns @err.
> + *
> + */
> +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);
> +
> +       va_end(args);
> +
> +       return err;
> +}
> +EXPORT_SYMBOL_GPL(probe_err);
> +
>  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 6cb4640b6160..2d3a1cc6f5da 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -1591,6 +1591,9 @@ do {                                                                      \
>         WARN_ONCE(condition, "%s %s: " format, \
>                         dev_driver_string(dev), dev_name(dev), ## arg)
>
> +extern __printf(3, 4)
> +int probe_err(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
>