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    SubjectRe: [PATCH 1/3] driver core: add probe_err log helper
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    On 16.10.2018 13:01, Andy Shevchenko wrote:
    > On Tue, Oct 16, 2018 at 10:22 AM Andrzej Hajda <a.hajda@samsung.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 seqences 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@samsung.com>
    >> ---
    >> drivers/base/core.c | 37 +++++++++++++++++++++++++++++++++++++
    >> include/linux/device.h | 2 ++
    >> 2 files changed, 39 insertions(+)
    >>
    >> diff --git a/drivers/base/core.c b/drivers/base/core.c
    >> index 04bbcd779e11..23fabefb217a 100644
    >> --- a/drivers/base/core.c
    >> +++ b/drivers/base/core.c
    >> @@ -3067,6 +3067,43 @@ 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) {
    > Why not
    >
    > if (err == ...)
    > return err;
    >
    > ...
    > return err;
    >
    > ?
    >
    > Better to read, better to maintain. No?

    Yes, anyway next patch will re-factor it anyway.

    >
    >> + va_start(args, fmt);
    >> +
    >> + vaf.fmt = fmt;
    >> + vaf.va = &args;
    >> +
    >> + __dev_printk(KERN_ERR, dev, &vaf);
    > It would be nice to print an error code as well, wouldn't it?

    Hmm, on probe fail error is printed anyway (with exception of
    EPROBE_DEFER, ENODEV and ENXIO):
        "probe of %s failed with error %d\n"
    On the other side currently some drivers prints the error code anyway
    via dev_err or similar, so I guess during conversion to probe_err it
    should be removed then.

    If we add error code to probe_err is it OK to report it this way?
        dev_err(dev, "%V, %d\n", &vaf, err);

    Regards
    Andrzej

    >
    >> + va_end(args);
    >> + }
    >> +
    >> + return 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 90224e75ade4..06c2c797d132 100644
    >> --- a/include/linux/device.h
    >> +++ b/include/linux/device.h
    >> @@ -1577,6 +1577,8 @@ do { \
    >> WARN_ONCE(condition, "%s %s: " format, \
    >> dev_driver_string(dev), dev_name(dev), ## arg)
    >>
    >> +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))
    >> --
    >> 2.18.0
    >>
    >

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