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Upgrading my Chumby 8 kernel part 11: SD/CF card reader
As my Chumby 8 kernel upgrade project neared the finish line (read parts 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 first if you want), I noticed something subtly annoying. The built-in SD/CF card reader was allocating its own dummy block device (/dev/sda) even if no cards were inserted.
When the pins changed, it alerted a program running in userspace so it could reset the port to cause the kernel to redetect, and possibly ignore, the card reader device. It turns out that the usb-storage driver has a useful “quirks” kernel command line parameter that can be used to, among many other things, tell it to ignore devices by their USB vendor and product ID. After the kernel is booted, run a userspace daemon that removes the quirk and manually connects and disconnects the card reader device based on the detection pins.
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