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Linux - Embedded & Single-board computer This forum is for the discussion of Linux on both embedded devices and single-board computers (such as the Raspberry Pi, BeagleBoard and PandaBoard). Discussions involving Arduino, plug computers and other micro-controller like devices are also welcome.

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Old 10-03-2014, 08:22 PM   #1
EmmanuelJ
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SD card autodetect and scan


Hi

I am using linux 2.6.39 and a USB-SD card controller (Ultra Fast Media by Generic). I would like to detect and scan SD card upon instertion even. I googled about it and I could not find a complete solution.

I read about enabling in kernel polling etc. I dont know how to use it for sd card autodetection.

Please let me know. Thanks a lot

Emmanuel
 
Old 10-04-2014, 08:56 PM   #2
aus9
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kernel polling howto
http://ignorantguru.github.io/spacef...vices-kernpoll

2) What file manager you use and what settings it has.

eg I use thunar from XFCE and go into preferences (=settings) and enable volume management
then in volume management which is linked to either by thunar preferences or xfce settings....removeable drives and media
I have these settings
--hot-plugging enabled
--auto mount removeable media when inserted
--browser media when inserted

good luck
 
Old 10-06-2014, 08:10 PM   #3
EmmanuelJ
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SD card autodetect and scan

Thanks aus9 for your reply. The link you provided is more clear on how to enable kernel-polling.

I am harding coding the kernel driver block/genhd.c to enable in-kernel-polling.

In disk_add_events()
ev->disk = disk;
spin_lock_init(&ev->lock);
ev->block = 1;
ev->poll_msecs = 2000;
INIT_DELAYED_WORK(&ev->dwork, disk_events_workfn);

Then I added some prints in disk_events_workfn(), which is called every 2 seconds.
disk_events_workfn() checks for events and strobes a KOBJ_CHANGE event if there is media change.
If I reboot my board without SD card inserted and with the above changes in kernel, I see prints in the disk_events_workfn() every two seconds.

Now here is my problem:
If I reboot my board with SD card inserted and with the above changes in kernel, I see the my SD card is scanned and see prints of its size and partition name sda1... But I dont see my prints in disk_events_workfn(), which may mean the polling is stopped.
Is that normal? once the SD card card is scanned there wont be any more polling? I want the polling to be on, so that it should be rescanned even if I replace it with another SD card or inserted it again.


I am working an embedded platform, and not sure about the filesystem manager.

Thanks again
Emmanuel
 
Old 10-13-2014, 08:17 PM   #4
aus9
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sorry I have no experience of embedded devices

for me, if I want to swap something in my usb hub card reader I remove the card reader and swap sdcards and re-insert.
its simple but it works for me
 
  


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