[PATCH] driver core: Clarify that dev_err_probe() is OK even w/out -EPROBE_DEFER

[PATCH] driver core: Clarify that dev_err_probe() is OK even w/out -EPROBE_DEFER

[Douglas Anderson]

There is some debate about whether it's deemed acceptable to call
dev_err_probe() if you know that the error code can never be
-EPROBE_DEFER. Clarify in the function comments that this is
OK. Specifically this makes us able to transform code like this:

  ret = do_something_that_cant_defer();
  if (ret < 0) {
    dev_err(dev, "The foo failed to bar (%pe)\n", ERR_PTR(ret));
    return ret;
  }

to code like this:
  ret = do_something_that_cant_defer();
  if (ret < 0)
    return dev_err_probe(dev, ret, "The foo failed to bar\n");

It is also possible that in the future folks might want a CONFIG
option to strip out all probe error strings to save space (keeping
non-probe errors) with the argument that probe errors rarely happen
after bringup. Having probe errors reported with a consistent function
would allow that.

Cc: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

 drivers/base/core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index e65dd803a453..85b8955717fc 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -4653,6 +4653,11 @@ define_dev_printk_level(_dev_info, KERN_INFO);
  *
  * 	return dev_err_probe(dev, err, ...);
  *
+ * Note that it is deemed acceptable to use this function for error
+ * prints during probe even if the @err is known to never be -EPROBE_DEFER.
+ * The benefit compared to a normal dev_err() is the standardized format
+ * of the error code and the fact that the error code is returned.
+ *
  * Returns @err.
  *
  */
-- 
2.33.0.464.g1972c5931b-goog

Re: [PATCH] driver core: Clarify that dev_err_probe() is OK even w/out -EPROBE_DEFER

[Greg KH]

On Thu, Sep 16, 2021 at 04:19:40PM -0700, Douglas Anderson wrote:
> There is some debate about whether it's deemed acceptable to call
> dev_err_probe() if you know that the error code can never be
> -EPROBE_DEFER. Clarify in the function comments that this is
> OK. Specifically this makes us able to transform code like this:
> 
>   ret = do_something_that_cant_defer();
>   if (ret < 0) {
>     dev_err(dev, "The foo failed to bar (%pe)\n", ERR_PTR(ret));
>     return ret;
>   }
> 
> to code like this:
>   ret = do_something_that_cant_defer();
>   if (ret < 0)
>     return dev_err_probe(dev, ret, "The foo failed to bar\n");
> 
> It is also possible that in the future folks might want a CONFIG
> option to strip out all probe error strings to save space (keeping
> non-probe errors) with the argument that probe errors rarely happen
> after bringup. Having probe errors reported with a consistent function
> would allow that.
> 
> Cc: Stephen Boyd <swboyd@chromium.org>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
> 
>  drivers/base/core.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index e65dd803a453..85b8955717fc 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -4653,6 +4653,11 @@ define_dev_printk_level(_dev_info, KERN_INFO);
>   *
>   * 	return dev_err_probe(dev, err, ...);
>   *
> + * Note that it is deemed acceptable to use this function for error
> + * prints during probe even if the @err is known to never be -EPROBE_DEFER.
> + * The benefit compared to a normal dev_err() is the standardized format
> + * of the error code and the fact that the error code is returned.
> + *
>   * Returns @err.
>   *
>   */
> -- 
> 2.33.0.464.g1972c5931b-goog
> 

Nice, no objection from me, I'll go queue this up.

greg k-h