On Fri, Feb 05, 2021 at 10:28:32AM -0800, Guenter Roeck wrote:

On Fri, Feb 05, 2021 at 05:44:13PM +0800, Yicong Yang wrote:

quoted

From: Junhao He <redacted>

Use subdir-ccflags-* instead of ccflags-* to inherit the debug
settings from Kconfig when traversing subdirectories.

Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Junhao He <redacted>
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>

What problem does this fix ? Maybe I am missing it, but I don't see
DEBUG being used in a subdirectory of drivers/hwmon.

It's my fault for raising this question [1].  Yicong fixed a real
problem in drivers/pci, where we are currently using

  ccflags-$(CONFIG_PCI_DEBUG) := -DDEBUG

so CONFIG_PCI_DEBUG=y turns on debug in drivers/pci, but not in the
subdirectories.  That's surprising to users.

So my question was whether we should default to using subdir-ccflags
for -DDEBUG in general, and only use ccflags when we have
subdirectories that have their own debug options, e.g.,

  drivers/i2c/Makefile:ccflags-$(CONFIG_I2C_DEBUG_CORE) := -DDEBUG
  drivers/i2c/algos/Makefile:ccflags-$(CONFIG_I2C_DEBUG_ALGO) := -DDEBUG
  drivers/i2c/busses/Makefile:ccflags-$(CONFIG_I2C_DEBUG_BUS) := -DDEBUG
  drivers/i2c/muxes/Makefile:ccflags-$(CONFIG_I2C_DEBUG_BUS) := -DDEBUG

I mentioned drivers/hwmon along with a few others that have
subdirectories, do not have per-subdirectory debug options, and use
ccflags.  I didn't try to determine whether those subdirectories
currently use -DDEBUG.

In the case of drivers/hwmon, several drivers do use pr_debug(),
and CONFIG_HWMON_DEBUG_CHIP=y turns those on.  But if somebody
were to add pr_debug() to drivers/hwmon/occ/common.c, for example,
CONFIG_HWMON_DEBUG_CHIP=y would *not* turn it on.  That sounds
surprising to me, but if that's what you intend, that's totally fine.

[1] https://lore.kernel.org/r/20210204161048.GA68790@bjorn-Precision-5520 (local)

quoted

---
 drivers/hwmon/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 09a86c5..1c0c089 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile

@@ -201,5 +201,5 @@ obj-$(CONFIG_SENSORS_XGENE)	+= xgene-hwmon.o
 obj-$(CONFIG_SENSORS_OCC)	+= occ/
 obj-$(CONFIG_PMBUS)		+= pmbus/
 
-ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
+subdir-ccflags-$(CONFIG_HWMON_DEBUG_CHIP) := -DDEBUG
 

-- 
2.8.1