My Multi-Slot USB card reader didnt work exactly how i liked itout the box, so i made a few tweaks.
Here's how and why.

my Card reader is a 21 in 1 Memory card reader, which has 4 slots for cards, and is capable of using upto 4 different cards at once.

All 4 cards run off the SAME single usb connection (without an internal USB hub)

This adds an unseen consiquence.
Bu doing this, we forfeit USB's hot plug abilities.

For example, a single card reader will use its hotplug abbility's to reset the usb drivers when a new card is inserted or removed, causing the kernel to re-scan the device, and detect vital things like the cards size, partiton table read/write etc etc.

Multi slots cannot do this.
Imagine One card is in use, and we insert a second, if the device was to use the normal hot-plug trigger, the in use device would be re-set. possably losing data.

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Question: Ahaaaaa !
But windows seems to be able to detect new cards beeing inserted just fine !
and without upsetting other cards in use... How does windows do this ?
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Answer: Windows does not use the hotplug usb feature either, it polls each of the 4 slots every second or 2, asking them if they have a card inserted, if the answer changes from no to yes, it knows a card was inserted, if the answer changes from yes to no, it knows a card was removed.
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So, a simple solution may be to implement the windows method into a linux script.
The script would be fairly simple, somthing like


replace X with the slot character [a-z]

This script loops round checking the usb card reader for new cards every second.
if a card is in use, the script waits 10 seconds untill it continues checking.

This basically how windows does it.
BUT i hate this method for 3 reasons.

1) The disk activity light constantly flickers, annoying, as my card reader is eye hight, and its distracting.
2) Its a messy solution, and possably slows down performance of the card reader.
3) it fills the messages log will /dev/sdX is busy mesages.

People are always saying how customisable linux is, and how its so easy.. so lets show off, and
make a better solution.

BUT first off, lets make sure your multi slot cad reader is working.

make sure the following modules are loaded (run lsmod as root, and look for the following enteries)



if any of those are missing, run the following comand as root, for each missing module



if the above command ever returns a module not found, dont worry, the module if porbabl in-bult into your kernel by your distro makers, and noesnt need to be loaded speratly.

now, just to make sure your card reader is supported, run the following command.



you should see output similar to the following.
NOTE: you will have extra enteries if you also have SCSI disks as opposed to IDE disks.
If you dont know what SCSI is, you probably dont have SCSI disks



look at the "lun x" enteries, you SHOULD see on lun for each slot in your card reader.
i have lun 0 to lun 3 (4 slots)

If you only see one lun, and have more than 1 slot, your kernel needs a re-compile.
This is very un-likely, but if this is you, reply here, and i wil help you do this.

basically you need to go to
Device Drivers -> SCSI ->
and select "PROBE ALL LUNS ON SCSI DEVICE"

and re-compile.

Each slot will be accessable as a differant /dev/sdX1 device.

Insert your memory cards, then un-plug the reader, and plug it back in.

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QUESTION: why did we have to re-plug it in ?

ANSWER:
Remember what i talked about above ?
because no cards were inserted when you turned the computer on / loaded the drivers, then no cards were detected, linux has not re-scanned the device, so still thinks no cards are inserted, re-plugging it in, caused linux to re-scan the device and find new cards.
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I am NOW going to show you how to make linux re-scan for new cards all by itself, when needed, withoout user interaction.

you will need to install sudo if sudo is not already installed (it probably is !)

edit /etc/sudoers with the following command AS ROOT



and add the following line. to the end of the file.



this will allow normal users to probe the memory cards without the root password
(if you have more than 5 SCSI devices + memory card slots, edit the "[a-e]"
if in doubt [a-z] will allow ou to use all of them.

now make some mount points for your memry cards.



now edit /etc/fstab
add the following lines



AND FINALLY....
we are going to program a *FAKE MOUNT*

The job of this, is to replace the real mount.
it will snoop at what the computer wants mount to do.
if mount is beeing called to mount a memory card, it will probe that card first.
re-scanning its partiton table.

cd into /bin/ and rename the mount program



now add the fake mount.
save the following file as root, to /bin/mount.





now make the script executable


This little script is quite simple, if you call mount with parameter "/mnt/sd[a-d]"
the script will instruct the kernel to re-scan the device you are about to mount.

it then waits upto 3 seconds for the kernel to find a card, and add a /dev/sd[a-d]1 device node.

it then passes control to the real mount.

If you are NOT mounding a usb card reader show, control is passed instantly to the real mount.

Try it out, you should now be ableo to mound your cards like so



or with KDE's graphical mount tools (or gnome / whatever graphical envronment you use)

So, what do you think ??
Better solution that constant probing ? or do you prefere the Windows method ?

 

 

 

Reply

I have only 4 readers, 2 types of cards each, also on a single USB slot.
Do you really know people using multi-slot card reader with several simultaneous media ?
I only have one card in my multi-reader, but I am sure if I had several cards I would have the same behaviour.
I use the cards in my photo camera, in order to cleanup my camera memory card and put it on the disk.

1) I remove the memory card from my photo camera.
2) I insert the card in my multi-reader.
3) Windows XP opens a explorer window.
4) I click on my pictures directory.
5) Edit, select all, edit, cut.
6) Go to my hard disk, my_camera subfolder.
7) Edit, paste.
8) Go to the windows taskbar, "safely disconnect a peripheral", disconnect my card reader.
9) Remove the card from the PC reader.
10) insert the card in my camera.
11) Remove the second memory card from my camera.
12) go to 2.

So, I never had two cards at the same moment, and I cleaned the Windows cache in order not to have things in cache when removing the card.
I guess it's the only safe way, so everybody should do that way, no matter how many how many memory cards you own

 

 

 

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If you actually READ this tutorial, you would have noticed..

1) This tutorial if for making memory cards hot-pluggable for LINUX
2) Windows already does this by default by probing the device on a continuous loop. (which i personally think is messy, and a waste of resources).

By following this tutorial, linux users will be able to use memory cards that were NOT inserted dureing boot up.

Otherwise, i user would need to unplug the usbn card reader, or re load the drivers, OR run hdparm -z /dev/sdX manually.

please read a post before replying, otherwise it just clutters up the thread with nonsens like the second and third reply to this tutorial.

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@qwijibow : you are right when you give a full tutorial for Linux users.
I just wanted to point out how standard Windows users should do if they have the same kind of reader and do not want to loose date. Few hardware knowledge can sometimes avoid big software trouble.
Sorry for having disturbed your nice post, that was my first error and should be my last one.

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Lol, no porblem.
I assumed you didnt notice this was in the linux section.
Your instruction would be better suited to a windows section

Please keep windows specific tutorials out of the linux section.

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Script version 1.1 (to replace script in first post)
Install instructions within the script.

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for me, it's insert memory card into computer, voila!

xboxrulz

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