We have a macro that takes a right-justified contiguous set of bits and shifts
it left to create a bitmask:
#define FOO(m, s) (m) << (s)
where m is in hex and s is an integer. I'd like to transform occurrences of it
to the Linux kernel's GENMASK(high, low) macro (which creates a contiguous
bitmask starting at bit position low and ending at position high), but am
having problems trying to figure out how to do that.
For example, I'd like to transform:
#define BITMASK_A FOO(0x3F, 4) /*
0x3F0 */
to
#define BITMASK_A GENMASK(9, 4) /* 0x3F0
*/
The value s in FOO() is the same as the value low in GENMASK(), but the value
high in GENMASK() must be calculated from the values m and s in FOO(). One
calculation would be to use the hamming weight (hweight) such as hweight(m) + s
- 1. My Python-foo is non-existent but I have found online an example for
calculating the hamming weight with the Python script 'def hweight(n): return
bin(n).count("1")'. Is it possible to use this (or another) Python script in a
Coccinelle script to do this transform, and if so, what would that look like?
If the transform cannot use Python, is there another suggestion?
Thanks,
Bruce.
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