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

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Date:   Thu, 16 Sep 2021 16:19:40 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     gregkh@...uxfoundation.org, rafael@...nel.org
Cc:     broonie@...nel.org, andy.shevchenko@...il.com, a.hajda@...sung.com,
        Douglas Anderson <dianders@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] driver core: Clarify that dev_err_probe() is OK even w/out -EPROBE_DEFER

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@...omium.org>
Signed-off-by: Douglas Anderson <dianders@...omium.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