Re: [PATCH] tracing: Add bitmask-list option for human-readable bitmask display

On Mon, 22 Dec 2025 22:56:22 -0500
Aaron Tomlin [off-list ref] wrote:

Add support for displaying bitmasks in human-readable list format (e.g.,
0,2-5,7) in addition to the default hexadecimal bitmap representation.
This is particularly useful when tracing CPU masks and other large
bitmasks where individual bit positions are more meaningful than their
hexadecimal encoding.

When the "bitmask-list" option is enabled, the printk "%*pbl" format
specifier is used to render bitmasks as comma-separated ranges, making
trace output easier to interpret for complex CPU configurations and
large bitmask values.

Hmm, I have a couple of issues with this change. One, this is global. It
affects all instances. The other is that if this is going to be done, then
instead of adding a parameter to trace_seq_bitmask(), another trace_seq_*
API should be created. Perhaps trace_seq_bitmask_cnt()? And have
trace_print_bitmask_seq() call them separately.

I'm still not convinced that this is needed. What examples do you see?
Should it be only for CPU bitmasks?

I think a bit more thought needs to be made on a change like this. There's
other options that were added that I now regret. I don't want to add
another one I wish we didn't have.

-- Steve