bw_report is only needed for selecting the correct value from the
values IMC measured. It is a member in the resctrl_val_param struct and
is always set to "reads". The value is then checked in resctrl_val()
using validate_bw_report_request() that besides validating the input,
assumes it can mutate the string which is questionable programming
practice.
Simplify handling bw_report:
- Convert validate_bw_report_request() into get_bw_report_type() that
inputs and returns const char *. Use NULL to indicate error.
- Validate the report types inside measure_mem_bw(), not in
resctrl_val().
- As resctrl_val() no longer needs bw_report for anything, it can just
be passed to measure_mem_bw() by the ->measure() hooks.
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
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