From mboxrd@z Thu Jan  1 00:00:00 1970
From: Kay Sievers <kay.sievers@vrfy.org>
Date: Tue, 20 Jan 2004 02:52:30 +0000
Subject: how to determine physical bus of a device and find it there
Message-Id: <20040120025230.GA26199@vrfy.org>
List-Id: <linux-hotplug.vger.kernel.org>
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To: linux-hotplug@vger.kernel.org


Hi,
I want to collect all possible attributes of a device with the udevinfo
program. This issue is also still unresolved with udev.

We need to determine the device on its physical bus not only the logical.
Here is a example for a usb-storage device with its logical 'scsi' and
physical 'usb' bus:

First I look in the hotplug provided directory and I find:

/sys/block/sda

  SYSFS_dev="8:0"
  SYSFS_range="16"
  SYSFS_size="31360"
  SYSFS_stat="      12        0       96       87        0        0 0        0        0       87       87"

then following the "device" link, I get on the scsi bus
/sys/devices/pci0000:00/0000:00:1d.0/usb1/1-1/1-1:1.0/host5/5:0:0:0

  SYSFS_detach_state="0"
  SYSFS_type="0"
  SYSFS_vendor="SMSC    "
  SYSFS_device_blocked="0"
  SYSFS_queue_depth="1"
  SYSFS_scsi_level="3"
  SYSFS_model="USB 2 HS-CF"
  SYSFS_rev="1.25"
  SYSFS_online="1"

but the really interesting attributes are on the usb bus:
/sys/devices/pci0000:00/0000:00:1d.0/usb1/1-1':

  SYSFS_detach_state="0"
  SYSFS_bNumConfigurations="1"
  SYSFS_bNumInterfaces=" 1"
  SYSFS_bConfigurationValue="1"
  SYSFS_bmAttributes="80"
  SYSFS_bMaxPower=" 48mA"
  SYSFS_idVendor="0424"
  SYSFS_idProduct="20fc"
  SYSFS_bcdDevice="0125"
  SYSFS_bDeviceClass="00"
  SYSFS_bDeviceSubClass="00"
  SYSFS_bDeviceProtocol="00"
  SYSFS_speed="12"
  SYSFS_manufacturer="SMSC"
  SYSFS_product="USB 2 Flash Media Device"
  SYSFS_serial="0305037000C2"


So, how do I reliable get there?
Do I need to extract the information from the path,
but what part of the string I can take out?
Shouldn't the kernel provide a link?
Do we need some magic here :)

thanks,
Kay


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