It's not uncommon that voltage regulator becomes available later during
kernel's boot process, in this case there is no need to print a noisy
error message. This patch moves the message about unavailable regulator
to the debug level in a case of the deferred-probe error and also amends
the message with error code.
Signed-off-by: Dmitry Osipenko <[email protected]>
---
drivers/iio/magnetometer/ak8974.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/iio/magnetometer/ak8974.c b/drivers/iio/magnetometer/ak8974.c
index d32996702110..cc3861f97d42 100644
--- a/drivers/iio/magnetometer/ak8974.c
+++ b/drivers/iio/magnetometer/ak8974.c
@@ -718,6 +718,7 @@ static const struct regmap_config ak8974_regmap_config = {
static int ak8974_probe(struct i2c_client *i2c,
const struct i2c_device_id *id)
{
+ const char *level = KERN_ERR;
struct iio_dev *indio_dev;
struct ak8974 *ak8974;
unsigned long irq_trig;
@@ -746,7 +747,11 @@ static int ak8974_probe(struct i2c_client *i2c,
ARRAY_SIZE(ak8974->regs),
ak8974->regs);
if (ret < 0) {
- dev_err(&i2c->dev, "cannot get regulators\n");
+ if (ret == -EPROBE_DEFER)
+ level = KERN_DEBUG;
+
+ dev_printk(level, &i2c->dev, "cannot get regulators: %d\n",
+ ret);
return ret;
}
--
2.26.0
Hi Dmitry,
thanks for your patch!
On Wed, Apr 15, 2020 at 12:27 AM Dmitry Osipenko <[email protected]> wrote:
> It's not uncommon that voltage regulator becomes available later during
> kernel's boot process, in this case there is no need to print a noisy
> error message. This patch moves the message about unavailable regulator
> to the debug level in a case of the deferred-probe error and also amends
> the message with error code.
>
> Signed-off-by: Dmitry Osipenko <[email protected]>
> ---
> drivers/iio/magnetometer/ak8974.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/magnetometer/ak8974.c b/drivers/iio/magnetometer/ak8974.c
> index d32996702110..cc3861f97d42 100644
> --- a/drivers/iio/magnetometer/ak8974.c
> +++ b/drivers/iio/magnetometer/ak8974.c
> @@ -718,6 +718,7 @@ static const struct regmap_config ak8974_regmap_config = {
> static int ak8974_probe(struct i2c_client *i2c,
> const struct i2c_device_id *id)
> {
> + const char *level = KERN_ERR;
> struct iio_dev *indio_dev;
> struct ak8974 *ak8974;
> unsigned long irq_trig;
> @@ -746,7 +747,11 @@ static int ak8974_probe(struct i2c_client *i2c,
> ARRAY_SIZE(ak8974->regs),
> ak8974->regs);
> if (ret < 0) {
> - dev_err(&i2c->dev, "cannot get regulators\n");
> + if (ret == -EPROBE_DEFER)
> + level = KERN_DEBUG;
> +
> + dev_printk(level, &i2c->dev, "cannot get regulators: %d\n",
This misses some important aspects of dev_dbg(), notably this:
#if defined(CONFIG_DYNAMIC_DEBUG)
#define dev_dbg(dev, fmt, ...) \
dynamic_dev_dbg(dev, dev_fmt(fmt), ##__VA_ARGS__)
#elif defined(DEBUG)
#define dev_dbg(dev, fmt, ...) \
dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__)
#else
#define dev_dbg(dev, fmt, ...) \
({ \
if (0) \
dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__); \
})
#endif
If DEBUG is not defined the entire dev_dbg() message is enclodes in if (0)
and compiled out of the kernel, saving space. The above does not
fulfil that.
Yours,
Linus Walleij
16.04.2020 14:33, Linus Walleij пишет:
> Hi Dmitry,
>
> thanks for your patch!
>
> On Wed, Apr 15, 2020 at 12:27 AM Dmitry Osipenko <[email protected]> wrote:
>
>> It's not uncommon that voltage regulator becomes available later during
>> kernel's boot process, in this case there is no need to print a noisy
>> error message. This patch moves the message about unavailable regulator
>> to the debug level in a case of the deferred-probe error and also amends
>> the message with error code.
>>
>> Signed-off-by: Dmitry Osipenko <[email protected]>
>> ---
>> drivers/iio/magnetometer/ak8974.c | 7 ++++++-
>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/iio/magnetometer/ak8974.c b/drivers/iio/magnetometer/ak8974.c
>> index d32996702110..cc3861f97d42 100644
>> --- a/drivers/iio/magnetometer/ak8974.c
>> +++ b/drivers/iio/magnetometer/ak8974.c
>> @@ -718,6 +718,7 @@ static const struct regmap_config ak8974_regmap_config = {
>> static int ak8974_probe(struct i2c_client *i2c,
>> const struct i2c_device_id *id)
>> {
>> + const char *level = KERN_ERR;
>> struct iio_dev *indio_dev;
>> struct ak8974 *ak8974;
>> unsigned long irq_trig;
>> @@ -746,7 +747,11 @@ static int ak8974_probe(struct i2c_client *i2c,
>> ARRAY_SIZE(ak8974->regs),
>> ak8974->regs);
>> if (ret < 0) {
>> - dev_err(&i2c->dev, "cannot get regulators\n");
>> + if (ret == -EPROBE_DEFER)
>> + level = KERN_DEBUG;
>> +
>> + dev_printk(level, &i2c->dev, "cannot get regulators: %d\n",
>
> This misses some important aspects of dev_dbg(), notably this:
>
> #if defined(CONFIG_DYNAMIC_DEBUG)
> #define dev_dbg(dev, fmt, ...) \
> dynamic_dev_dbg(dev, dev_fmt(fmt), ##__VA_ARGS__)
> #elif defined(DEBUG)
> #define dev_dbg(dev, fmt, ...) \
> dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__)
> #else
> #define dev_dbg(dev, fmt, ...) \
> ({ \
> if (0) \
> dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__); \
> })
> #endif
>
> If DEBUG is not defined the entire dev_dbg() message is enclodes in if (0)
> and compiled out of the kernel, saving space. The above does not
> fulfil that.
Hello Linus,
After some recent discussions in regards to the EPROBE_DEFER handling,
Thierry Reding suggested the form which is used in my patch and we
started to use it recently in the Tegra DRM driver [1]. The reason is
that we don't want to miss any deferred-probe messages under any
circumstances, for example like in a case of a disabled DYNAMIC_DEBUG.
The debug messages are usually disabled in a release-build and when not
a very experienced person hands you KMSG for diagnosing a problem, the
KMSG is pretty much useless if error is hidden silently.
By moving the message to a debug level, we reduce the noise in the KMSG
because usually people look for a bold-red error messages. Secondly, we
don't introduce an additional overhead to the kernel size since the same
text is reused for all error conditions.
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e32c8c2a5fbe1514e4ae9063a49e76ecf486ffb8
I can change this patch to something like this:
if (ret == -EPROBE_DEFER)
dev_dbg("deferring probe\n");
else
dev_err("cannot...");
but in general this should be a less useful variant, don't you agree?
On Thu, Apr 16, 2020 at 4:45 PM Dmitry Osipenko <[email protected]> wrote:
> 16.04.2020 14:33, Linus Walleij пишет:
> > This misses some important aspects of dev_dbg(), notably this:
> >
> > #if defined(CONFIG_DYNAMIC_DEBUG)
> > #define dev_dbg(dev, fmt, ...) \
> > dynamic_dev_dbg(dev, dev_fmt(fmt), ##__VA_ARGS__)
> > #elif defined(DEBUG)
> > #define dev_dbg(dev, fmt, ...) \
> > dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__)
> > #else
> > #define dev_dbg(dev, fmt, ...) \
> > ({ \
> > if (0) \
> > dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__); \
> > })
> > #endif
> >
> > If DEBUG is not defined the entire dev_dbg() message is enclodes in if (0)
> > and compiled out of the kernel, saving space. The above does not
> > fulfil that.
>
> Hello Linus,
>
> After some recent discussions in regards to the EPROBE_DEFER handling,
> Thierry Reding suggested the form which is used in my patch and we
> started to use it recently in the Tegra DRM driver [1]. The reason is
> that we don't want to miss any deferred-probe messages under any
> circumstances, for example like in a case of a disabled DYNAMIC_DEBUG.
I have a hard time to accept this reasoning.
Who doesn't feel that way about their subsystem? If you don't want
to miss the message under any circumstances then use dev_info().
Don't override the default behaviour of dev_dbg().
> The debug messages are usually disabled in a release-build and when not
> a very experienced person hands you KMSG for diagnosing a problem, the
> KMSG is pretty much useless if error is hidden silently.
So use dev_info().
> By moving the message to a debug level, we reduce the noise in the KMSG
> because usually people look for a bold-red error messages. Secondly, we
> don't introduce an additional overhead to the kernel size since the same
> text is reused for all error conditions.
dev_info() is not supposed to be an error message, it is supposed to
be information, so use that.
Yours,
Linus Walleij
16.04.2020 19:51, Linus Walleij пишет:
> On Thu, Apr 16, 2020 at 4:45 PM Dmitry Osipenko <[email protected]> wrote:
>> 16.04.2020 14:33, Linus Walleij пишет:
>
>>> This misses some important aspects of dev_dbg(), notably this:
>>>
>>> #if defined(CONFIG_DYNAMIC_DEBUG)
>>> #define dev_dbg(dev, fmt, ...) \
>>> dynamic_dev_dbg(dev, dev_fmt(fmt), ##__VA_ARGS__)
>>> #elif defined(DEBUG)
>>> #define dev_dbg(dev, fmt, ...) \
>>> dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__)
>>> #else
>>> #define dev_dbg(dev, fmt, ...) \
>>> ({ \
>>> if (0) \
>>> dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__); \
>>> })
>>> #endif
>>>
>>> If DEBUG is not defined the entire dev_dbg() message is enclodes in if (0)
>>> and compiled out of the kernel, saving space. The above does not
>>> fulfil that.
>>
>> Hello Linus,
>>
>> After some recent discussions in regards to the EPROBE_DEFER handling,
>> Thierry Reding suggested the form which is used in my patch and we
>> started to use it recently in the Tegra DRM driver [1]. The reason is
>> that we don't want to miss any deferred-probe messages under any
>> circumstances, for example like in a case of a disabled DYNAMIC_DEBUG.
>
> I have a hard time to accept this reasoning.
>
> Who doesn't feel that way about their subsystem? If you don't want
> to miss the message under any circumstances then use dev_info().
> Don't override the default behaviour of dev_dbg().
>
>> The debug messages are usually disabled in a release-build and when not
>> a very experienced person hands you KMSG for diagnosing a problem, the
>> KMSG is pretty much useless if error is hidden silently.
>
> So use dev_info().
>
>> By moving the message to a debug level, we reduce the noise in the KMSG
>> because usually people look for a bold-red error messages. Secondly, we
>> don't introduce an additional overhead to the kernel size since the same
>> text is reused for all error conditions.
>
> dev_info() is not supposed to be an error message, it is supposed to
> be information, so use that.
Okay, I'll make a v2. Thank you for the review.
On Thu, 16 Apr 2020 20:35:56 +0300
Dmitry Osipenko <[email protected]> wrote:
> 16.04.2020 19:51, Linus Walleij пишет:
> > On Thu, Apr 16, 2020 at 4:45 PM Dmitry Osipenko <[email protected]> wrote:
> >> 16.04.2020 14:33, Linus Walleij пишет:
> >
> >>> This misses some important aspects of dev_dbg(), notably this:
> >>>
> >>> #if defined(CONFIG_DYNAMIC_DEBUG)
> >>> #define dev_dbg(dev, fmt, ...) \
> >>> dynamic_dev_dbg(dev, dev_fmt(fmt), ##__VA_ARGS__)
> >>> #elif defined(DEBUG)
> >>> #define dev_dbg(dev, fmt, ...) \
> >>> dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__)
> >>> #else
> >>> #define dev_dbg(dev, fmt, ...) \
> >>> ({ \
> >>> if (0) \
> >>> dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__); \
> >>> })
> >>> #endif
> >>>
> >>> If DEBUG is not defined the entire dev_dbg() message is enclodes in if (0)
> >>> and compiled out of the kernel, saving space. The above does not
> >>> fulfil that.
> >>
> >> Hello Linus,
> >>
> >> After some recent discussions in regards to the EPROBE_DEFER handling,
> >> Thierry Reding suggested the form which is used in my patch and we
> >> started to use it recently in the Tegra DRM driver [1]. The reason is
> >> that we don't want to miss any deferred-probe messages under any
> >> circumstances, for example like in a case of a disabled DYNAMIC_DEBUG.
> >
> > I have a hard time to accept this reasoning.
> >
> > Who doesn't feel that way about their subsystem? If you don't want
> > to miss the message under any circumstances then use dev_info().
> > Don't override the default behaviour of dev_dbg().
> >
> >> The debug messages are usually disabled in a release-build and when not
> >> a very experienced person hands you KMSG for diagnosing a problem, the
> >> KMSG is pretty much useless if error is hidden silently.
> >
> > So use dev_info().
> >
> >> By moving the message to a debug level, we reduce the noise in the KMSG
> >> because usually people look for a bold-red error messages. Secondly, we
> >> don't introduce an additional overhead to the kernel size since the same
> >> text is reused for all error conditions.
> >
> > dev_info() is not supposed to be an error message, it is supposed to
> > be information, so use that.
>
> Okay, I'll make a v2. Thank you for the review.
Ah I commented on this in v2 - now I see why you did it :)
Nope to dev_info. That will often spam normal logs and as Andy pointed
out for v2 that can be dozens of entries on a sophisticated board. Much
better to stick to dev_dbg but I'd like to see it done explicitly in the
form you mention with the if / else
Thanks,
Jonathan
18.04.2020 17:37, Jonathan Cameron пишет:
> On Thu, 16 Apr 2020 20:35:56 +0300
> Dmitry Osipenko <[email protected]> wrote:
>
>> 16.04.2020 19:51, Linus Walleij пишет:
>>> On Thu, Apr 16, 2020 at 4:45 PM Dmitry Osipenko <[email protected]> wrote:
>>>> 16.04.2020 14:33, Linus Walleij пишет:
>>>
>>>>> This misses some important aspects of dev_dbg(), notably this:
>>>>>
>>>>> #if defined(CONFIG_DYNAMIC_DEBUG)
>>>>> #define dev_dbg(dev, fmt, ...) \
>>>>> dynamic_dev_dbg(dev, dev_fmt(fmt), ##__VA_ARGS__)
>>>>> #elif defined(DEBUG)
>>>>> #define dev_dbg(dev, fmt, ...) \
>>>>> dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__)
>>>>> #else
>>>>> #define dev_dbg(dev, fmt, ...) \
>>>>> ({ \
>>>>> if (0) \
>>>>> dev_printk(KERN_DEBUG, dev, dev_fmt(fmt), ##__VA_ARGS__); \
>>>>> })
>>>>> #endif
>>>>>
>>>>> If DEBUG is not defined the entire dev_dbg() message is enclodes in if (0)
>>>>> and compiled out of the kernel, saving space. The above does not
>>>>> fulfil that.
>>>>
>>>> Hello Linus,
>>>>
>>>> After some recent discussions in regards to the EPROBE_DEFER handling,
>>>> Thierry Reding suggested the form which is used in my patch and we
>>>> started to use it recently in the Tegra DRM driver [1]. The reason is
>>>> that we don't want to miss any deferred-probe messages under any
>>>> circumstances, for example like in a case of a disabled DYNAMIC_DEBUG.
>>>
>>> I have a hard time to accept this reasoning.
>>>
>>> Who doesn't feel that way about their subsystem? If you don't want
>>> to miss the message under any circumstances then use dev_info().
>>> Don't override the default behaviour of dev_dbg().
>>>
>>>> The debug messages are usually disabled in a release-build and when not
>>>> a very experienced person hands you KMSG for diagnosing a problem, the
>>>> KMSG is pretty much useless if error is hidden silently.
>>>
>>> So use dev_info().
>>>
>>>> By moving the message to a debug level, we reduce the noise in the KMSG
>>>> because usually people look for a bold-red error messages. Secondly, we
>>>> don't introduce an additional overhead to the kernel size since the same
>>>> text is reused for all error conditions.
>>>
>>> dev_info() is not supposed to be an error message, it is supposed to
>>> be information, so use that.
>>
>> Okay, I'll make a v2. Thank you for the review.
>
> Ah I commented on this in v2 - now I see why you did it :)
> Nope to dev_info. That will often spam normal logs and as Andy pointed
> out for v2 that can be dozens of entries on a sophisticated board. Much
> better to stick to dev_dbg but I'd like to see it done explicitly in the
> form you mention with the if / else
Alright, I'll make a v3.