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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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