[GTALUG] War story: OpenWRT USB access

Giles Orr gilesorr at gmail.com
Tue Jan 6 17:18:10 UTC 2015

I WAS going to point out it can be read in the original at
http://www.gilesorr.com/blog/archerc7-openwrt.html (with all
formatting), but a finger went astray and sent the message on its way.
Sorry about that.

On 6 January 2015 at 12:15, Giles Orr <gilesorr at gmail.com> wrote:
> In honour of Hugh's "war stories," which I enjoy and think/hope I'm
> learning from, here's one of my own about trying to get USB access on
> an OpenWRT router ... and the dangers of thinking you know what you're
> doing.  This is cut and pasted from my blog, so it'
> I've just purchased a TP-Link wireless access point. Despite owning
> the thing, the model of the item remains somewhat unclear: it's
> variously known as the "TL-WDR7500," "AC1750," and the "Archer C7."
> Fortunately, what was clear is that it has good specs (including
> immensely more memory than the WRT54Gs I've been playing with, and two
> USB2 ports), it's very well supported by OpenWRT (mine is the one with
> three antennas). This is a version 2, which is also good as that has
> more memory than version 1.x. And installing OpenWRT was literally as
> easy as downloading
> barrier_breaker/14.07/ar71xx/generic/openwrt-ar71xx-generic-archer-c7-v2-squashfs-factory.bin,
> logging in to the router's admin interface and then to "Firmware
> Upgrade," pointing to the downloaded file, and pressing the "Upgrade"
> button. It doesn't get much simpler than that.
> Getting OpenWRT to talk to the two USB ports on the device was
> unpleasantly difficult. With the default install, dmesgmade it clear
> that the insertion of a USB device was duly noted with a log entry
> like this:
> usb 2-1: new high-speed USB device number 3 using ehci-platform
> but there was no further information - perhaps noting whether or not
> it was a drive rather than a mouse? Or what device number it was. I
> started to work through the information at
> http://wiki.openwrt.org/doc/howto/usb.storage . So I installed:
> kmod-usb-storage
> kmod-scsi-core
> which you'd think would be in the default squashfs file for this
> specific device as they'd already included kmod-usb-core. I kind of
> understand why they didn't include the filesystem types (who knows
> which you're going to need?) so I installed:
> kmod-fs-msdos
> kmod-fs-vfat
> It was possible to do insmod kmod-usb-storage and insmod kmod-fs-vfat
> after these installs, but I found behaviour was better after a reboot:
> I have to assume there's scripts and autodetection that set these up
> better than a naked insmodcommand. Still, it's a bit annoying to have
> to reboot a Linux device as if it were Windows ...
> And finally I installed:
> block-mount
> which is apparently required to mount any device. Again, shouldn't
> that be in the default image?
> At this point, dmesg was acknowledging that we have genuine USB
> storage devices attached:
> usb 1-1: new high-speed USB device number 2 using ehci-platform
> usb-storage 1-1:1.0: USB Mass Storage device detected
> scsi0 : usb-storage 1-1:1.0
> scsi 0:0:0:0: Direct-Access     USB 3.0  USB Flash Drive 1.00 PQ: 0 ANSI: 6
> sd 0:0:0:0: [sda] 30883840 512-byte logical blocks: (15.8 GB/14.7 GiB)
> sd 0:0:0:0: [sda] Write Protect is off
> sd 0:0:0:0: [sda] Mode Sense: 23 00 00 00
> sd 0:0:0:0: [sda] Write cache: disabled, read cache: disabled, doesn't
> support DPO or FUA
>  sda: sda1
> sd 0:0:0:0: [sda] Attached SCSI removable disk
> But attempting to run mount /dev/sda1 /mnt/ fails with mount: mounting
> /dev/sda1 on /mnt/ failed: Invalid argument, although we do now have a
> /dev/sda1 device in the /dev/ folder and /mnt/ is a valid folder.
> After hours of tests and googling, I finally stumbled across an
> obscure hint from someone who was asking another question but had
> "solved the USB problem" ... they had installed the appropriate NLS
> ("Native Language Support") packages for their area. Seriously? But
> I'm willing to try anything by this point, so I installed:
> kmod-nls-iso8859-1
> kmod-nls-cp437
> Test again, and ... I can mount USB storage devices! At least ones
> with a filesystem that I've installed, so I guess I need to install
> NTFS and/or ext3/4 support if I want to use hard drives.
> This solution is both non-obvious and not well documented. I see in
> looking back at the OpenWRT documentation that they DO mention the NLS
> packages. But I didn't notice at the time and they weren't
> dependencies enforced by the package manager, so they got lost. <sigh>
> --
> Giles
> http://www.gilesorr.com/
> gilesorr at gmail.com

gilesorr at gmail.com

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