Re: [PATCH V3 0/3] OMAPDSS: Enable dynamic debug printing

On Fri, Sep 28, 2012 at 5:04 PM, Tomi Valkeinen [off-list ref] wrote:

On Fri, 2012-09-28 at 15:53 +0530, Chandrabhanu Mahapatra wrote:

quoted

Hi everyone,
this patch series aims at cleaning up of DSS of printk()'s enabled with
dss_debug and replace them with generic dynamic debug printing.

The 1st patch
 * moved DEBUG flag definition to Makefile
The 2nd patch
 * replaces printk() in DSSDBG definition with pr_debug()
 * removes DSSDBGF definition and replaces its instances with DSSDBG()
The 3rd patch
 * cleans up printk()'s in omap_dispc_unregister_isr() and
   _dsi_print_reset_status() with pr_debug()
 * removes dss_debug variable

Changes from V1 to V2:
 * added debug messages to DSSDBG calls
 * added patch "OMAPDSS: Remove dss_debug variable"

Changes from V2 to V3
 * added patch "OMAPDSS: Move definition of DEBUG flag to Makefile"

All your comments and suggestions are welcome.

There's one thing that's not quite nice about omapdss's debug print
behavior after this series.

CONFIG_OMAP2_DSS_DEBUG_SUPPORT is marked "default y", and it's also been
safe to enable earlier as we had the dss_debug variable to prevent the
debug prints. But after this series, the debug prints are enabled, and
will spam the kernel log quite heavily.

And that happens with both dynamic debugging enabled and disabled.

Yes, I had noticed that but I thought a better way to disable debug
prints is to disable both dynamic debugging (CONFIG_DYNAMIC_DEBUG) and
CONFIG_OMAP2_DSS_DEBUG_SUPPORT. May be CONFIG_OMAP2_DSS_DEBUG_SUPPORT
should have been false by default.

How things should work:

For kernels with dynamic debugging disabled: by default the dss debugs
are not compiled, and the user needs to explicitly enable them in the
kernel config.

For kernels with dynamic debugging enabled: by default the dss debugs
are compiled in, but not enabled. A Kconfig option can be set to make
the debugs enabled by default.

In addition to those, we have the debugfs files. Those should be usable
regardless of the debug prints.

So I suggest the following:

- Remove CONFIG_OMAP2_DSS_DEBUG_SUPPORT. We can't re-use it, because it
may be enabled in user's kernel configs.
- Add new Kconfig option: CONFIG_OMAP2_DSS_DEBUG. This will set DEBUG in
the makefile. This is off by default.
- Add new Kconfig option: CONFIG_OMAP2_DSS_DEBUGFS. This will be use to
decide if debugfs functionality is compiled in or not. This is off by
default.

 Tomi

Well, I had a different perception. If one needs to debug then both
debugfs and debug prints should be enabled. If one needs only debug
prints then CONFIG_DEBUG_FS can be disabled.
But above approach seems to provide more flexibilty.

-- 
Chandrabhanu Mahapatra
Texas Instruments India Pvt. Ltd.