On Tue, 2008-03-25 at 13:31 -0400, Mark Lord wrote: > James Bottomley wrote: > > On Tue, 2008-03-25 at 00:02 -0400, Mark Lord wrote: > >.. > >> Practically all utilities that care about it, > >> use ioctl(fd, HDIO_GETGEO) to determine the starting > >> sector offset of a hard disk partition. > .. > > Perhaps I've missed something, but surely geometry doesn't make sense on > > a >2TB drive does it? The only reason we use it on modern disks (which > > usually make it up specially for us) is that the DOS partition scheme > > requires it. Once we're over 2TB, isn't it impossible to use DOS > > partitions (well, OK, unless you increase the sector size, but that's > > only delaying the inevitable), so we can just go with a proper disk > > labelling scheme and use BLKGETSIZE64 all the time. > .. > > I haven't thought much about problems with the virtual geometry, > because, as you say, we really don't care about it for the most part. > We use LBA values from the partition tables rather than CHS. > I suppose those also likely to be 32-bit limited. > > The "partition offset", or "starting sector" is the important > bit of information for most things. And that's currently available > from HDIO_GETGEO, and from /sys/block/XXX/XXXn/start, if sysfs is mounted. > > We just need an easy way to get it, given a dev_t from stat(2). > Currently there isn't an easy way, and HDIO_GETGEO returns > only 32-bits on a 32-bit system. But I think where this is leading is that you've been using the geometry call, but all you really want to know is the actual partition start in sector units, so a new BLKGETPARTSTART (or something) ioctl that was designed to return a u64 would work for you? That sounds reasonable to me; so not a HDIO_GETGEO64 which gets us into trouble with geometries, but a simple ioctl that gives you exactly what you're looking for. James -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
