On Tue, Apr 24, 2012 at 6:57 AM, Michael Hudson-Doyle
<[email protected]> wrote:
> Part of the whole SD card mux game involves finding the card reader the SD
> card for a particular board is plugged into.
>
> Following a lead provided by Zygmunt, it seems that you can address
> devices by USB topology by looking in /sys/bus/usb/devices/ -- for
> example, the front right USB port on my laptop seems to correspond to a
> directories called "1-1.2" and "1-1.2:1.0" in here, the back left port
> corresponds to "3-1" and "3-1:1.0" and a particular port on a USB hub
> plugged into the front left USB port seems to correspond to "2-1.2.3"
> and "2-1.2.3:1.0". So this seems to be reasonably straightforward
> (although I don't know if the mapping is necessarily stable across
> reboots or kernel upgrades -- seems like it should be though).
I would think it's very risky to hope that we can identify the ports
this way across reboots. I hoped maybe we could identify individual
USB controllers across reboots ... in that sense we could plug in one
controler for each board... but then checking lsbusb -vv on my two PCI
USB controllers I get:
00:1a.0 USB controller: Intel Corporation 6 Series/C200 Series Chipset
Family USB Enhanced H
ost Controller #2 (rev 04) (prog-if 20 [EHCI])
Subsystem: Lenovo Device 21da
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
ParErr- Stepping- SERR-
FastB2B- DisINTx-
Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium
>TAbort- <TAbort- <MAbort- >
SERR- <PERR- INTx-
Latency: 0
Interrupt: pin A routed to IRQ 16
Region 0: Memory at f262a000 (32-bit, non-prefetchable) [size=1K]
Capabilities: <access denied>
Kernel driver in use: ehci_hcd
00:1d.0 USB controller: Intel Corporation 6 Series/C200 Series Chipset
Family USB Enhanced Host Controller #1 (rev 04) (prog-if 20 [EHCI])
Subsystem: Lenovo Device 21da
Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
ParErr- Stepping- SERR- FastB2B- DisINTx-
Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium
>TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
Latency: 0
Interrupt: pin A routed to IRQ 23
Region 0: Memory at f2629000 (32-bit, non-prefetchable) [size=1K]
Capabilities: <access denied>
Kernel driver in use: ehci_hcd
I cannot spot anything that feels safe to assume staying the same
across reboots :/... at best check with the #linaro-kernel friends to
get a negative on this idea quick :).
--
Alexander Sack
Technical Director, Linaro Platform Teams
http://www.linaro.org | Open source software for ARM SoCs
http://twitter.com/#!/linaroorg - http://www.linaro.org/linaro-blog
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