* Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:
> Hi Ingo,
>
> On 03/02/2017 02:40 PM, Ingo Molnar wrote:
> > * Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:
> >
> >> Hi Ingo,
> >>
> >> How about this version? Any further comments?
> > So I have re-read the review feedback I gave on Jan 19 and found at least one
> > thing I pointed out that you didn't address in the latest patches ...
>
> Do you mind telling me which one is not addressed? Is it one of below
> feedbacks?
So one piece of feedback I gave was:
| BTW., just a side note, some kernel developers (like PeterZ - and I do it
| sometimes too) remap early_printk to printk permanently and use it as their main
| printk facility - because printk() reliability has suffered over the last couple
| of years.
|
| So it's more than just early boot debugging - it's a very simple state-less
| logging facility to an external computer.
But the latest Kconfig help text still says this:
+config EARLY_PRINTK_USB_XDBC
+ bool "Early printk via the xHCI debug port"
+ depends on EARLY_PRINTK && PCI
+ select EARLY_PRINTK_USB
+ ---help---
+ Write kernel log output directly into the xHCI debug port.
+
+ This is useful for kernel debugging when your machine crashes very
+ early before the console code is initialized. For normal operation
+ it is not recommended because it looks ugly and doesn't cooperate
+ with klogd/syslogd or the X server. You should normally N here,
+ unless you want to debug such a crash.
... while in reality it's an alternative lockless logging facility that goes way
beyond debugging early boot crashes!
Granted, I qualified that with 'just a side note'. I guess something like this
would work:
+ One use for this feature is kernel debugging, for example when your
+ machine crashes very early before the regular console code is
+ initialized. Other uses include simpler, lockless logging instead of a
+ full-blown printk console driver + klogd.
+
+ For normal production environments this is normally not recommended,
+ because it doesn't feed events into klogd/syslogd and doesn't try to
+ print anything on the screen.
+
+ You should normally N here, unless you want to debug early crashes or
+ need a very simple printk logging facility.
Another piece of feedback I gave was:
> > +config USB_EARLY_PRINTK
> > + bool
>
> Also, could we standardize the nomencalture to not be a mixture of prefixes and
> postfixes - i.e. standardize on postfixes (as commonly done in the Kconfig
> space) and rename this one to EARLY_PRINTK_USB or so?
yet your latest submission still includes the very same postfixed config switch
name that collides with the prefixed names such as EARLY_PRINTK_USB:
--- a/drivers/usb/Kconfig
+++ b/drivers/usb/Kconfig
@@ -19,6 +19,9 @@ config USB_EHCI_BIG_ENDIAN_MMIO
config USB_EHCI_BIG_ENDIAN_DESC
bool
+config USB_EARLY_PRINTK
+ bool
+
menuconfig USB_SUPPORT
bool "USB support"
depends on HAS_IOMEM
The problem I tried to point out with my review feedback is that we thus have
both:
CONFIG_EARLY_PRINTK_USB=y
CONFIG_USB_EARLY_PRINTK=y
... which is confusing at the very least.
On a second look, this config switch appears to be unused - is it a leftover from
earlier patches?
The patches don't look too bad otherwise, so we are not far from having something
acceptable, IMHO.
Thanks,
Ingo
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