On 8/7/07, Neil Brown <[EMAIL PROTECTED]> wrote: > On Monday August 6, [EMAIL PROTECTED] wrote: > > On Tue, 2007-08-07 at 16:07 +1000, Neil Brown wrote: > > > Suppose that in a program I have an open file descriptor for a device, > > > and I want to find the /sys/block information for this device. > > > There is currently no direct way to do this. I need to read > > > /sys/block/*/dev, /sys/block/*/*/dev > > > and match major/minor numbers with the result from fstat. > > > > > > I would like a more direct mechanism.
$ udevinfo --query=path --name=sda /block/sda > > > The following patch is a proposal for such a mechanism. > > > > > > It provides an 'ioctl' which returns then 'name' of the device, as > > > generated by bdevname. This is the same name that is used to create > > > entries in sysfs. > > > For a partition of a device, it returns 'device/partition'. > > > > > > how about returning the entire path relative to the start of sysfs? That > > way, if things move or something you're tolerant against that.... > > That makes a lot of sense. > So it would return "block/sda/sda1" now, Every devpath always starts with a '/' in the kernel, its kind of weird, but we should not introduce a new variation of it. :) > but one day that might change > to "class/block/sda/sda1" or some-such. It will start with /devices/..., like: /sys/devices/pci0000:00/0000:00:1f.2/host0/target0:0:0/0:0:0:0/sda/sda1 > > (I'd not be against making this a generic IOCTL for every device, a > > SYSFSLOCATION kind of ioctl... it's by no means block specific...) > > > > That too seems very sensible. Only it's harder to choose a 'generic' > ioctl request number than to choose a block-specific one :-) > > We would also need a somewhat longer buffer. The longest > /sys/**/dev > path on my test machine is > /sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1:1.1/usb_endpoint/usbdev2.2_ep82/dev > > So at least 80 chars. Probably 256 would do.... They can be definitely longer than than 256, probably not longer than 512 today, but you can't be sure about that. Thanks, Kay - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
