How to detect when sdcard unplugged?

Autonomous Machines Jetson & Embedded Systems Jetson TX2
1

I use sdcard extension cable, so when I physically unplug sdcard, linux thinks, that card still plugged. Dir still mounted, fdisk show mmcblk2 device, I can read files from mount dir.
After several minutes, linux write errors to dmesg and remove sdcard.
But I want immediately know, when sdcard unplugged. Maybe, I can force rescan available sdcards?

2

Hi, what kind of cable are you using? System detects the card by a mechanical signal CARD_DETECT. Does the cable support that?

3

Hi
Cable like this Computer Memory Card Readers & Adapters for Sale - eBay

4

What about other normal SD card plug-in? same as this or not?

5

After some tries and googling, I solve this problem by script:

#!/bin/sh

MOUNT_DIR="/home/ubuntu/sdcard/"
TEST_FILE=".sdcard_test"

TEST_FILE_PATH=$MOUNT_DIR$TEST_FILE

try_mount_sdcard () {
    mkdir $MOUNT_DIR
    mount -o sync /dev/mmcblk2p1 $MOUNT_DIR
    result=$?
    if [ "$result" -eq "0" ]
    then
        echo "SDCard mounted succesfully"
    else
        rmdir $MOUNT_DIR
    fi
}

try_umount_sdcard () {
    umount -l $MOUNT_DIR
    umount -f $MOUNT_DIR
    rmdir $MOUNT_DIR
}

rebind_mmc () {
    echo 3400000.sdhci > /sys/bus/platform/drivers/sdhci-tegra/unbind
    sleep 1
    echo 3400000.sdhci > /sys/bus/platform/drivers/sdhci-tegra/bind
    sleep 1
}

sdcard_available () {
    mountpoint $MOUNT_DIR
    if [ "$?" -eq "1" ]
    then
        echo $MOUNT_DIR is not mount point, remove...
        rmdir $MOUNT_DIR
    fi

    rm $TEST_FILE_PATH
    touch $TEST_FILE_PATH
    if [ "$?" -eq "0" ]
    then
        rm $TEST_FILE_PATH
        echo "SDCard available"
        return 1
    else
        echo "SDCard unavailable"
        return 0
    fi
}

sdcard_available

if [ "$?" -eq "0" ]; then
    try_umount_sdcard
    rebind_mmc
    try_mount_sdcard
fi
6

Good to hear this, so it is driver problem not hardware issue.