Comment 75 for bug 952556

Thanks Steve. The problem, as you said, might be coming from a combination of causes. I have tried all the numbers that are mentioned here and elsewhere but in vain. The only magic number that has worked so far while switching to battery mode, as I said earlier is:

hdparm -B 128 -S 242 /dev/sda

There seems to be confusion about the -B and -S options. There also seems another tool (may be laptop mode?) that changes these settings by overriding the hdparm settings. I got some hint about the above -S option from an old Fedora forum, which means the issue isn't that recent. It has been there for several years. It is a bit of a shame that a tool adopted universally by all Linux disros is causing such an issue for so long. Apparently, hdparm has lots of options, some of which very naughty if not cared for, but one important option seems faulty or messed up by something else. According to Google, this behavior has been reported in every distro forum since 2000-. Its behavior seems to change with kernel. Does acpid has a role here? This really needs further digging and shall not be left at this stage 'as solved'.