Date: Wed, 13 May 2015 08:43:51 +0200 From: Polytropon <freebsd@edvax.de> To: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Using SD cards with automount / GUI notification Message-ID: <20150513084351.2be8f6fa.freebsd@edvax.de>
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What is the recommended use of built-in card readers in combination with device (and media) autodetection, followed by notification services (such as employed by desktop environments to make icons pop up)? This is essential for automount functionality that users (in single-user single-PC contexts) usually rely on. Think of how Gnome (as a "simple" example) handles removable devices. I'm asking because of the required "re-tasting" of the devices and how it fits into that concept. Initially, the device files corresponding to the different card slots are present: /dev/da[0-2] in this example. # camcontrol devlist <HL-DT-ST DVDRAM GSA-H42N RL00> at scbus0 target 0 lun 0 (pass0,cd0) <Generic Flash HS-CF 4.55> at scbus3 target 0 lun 0 (da0,pass1) <Generic Flash HS-MS/SD 4.55> at scbus3 target 0 lun 1 (da1,pass2) <- <Generic Flash HS-SM 4.55> at scbus3 target 0 lun 2 (da2,pass3) And therefore: # ls /dev/da* /dev/da0 /dev/da1 /dev/da2 After inserting a SD card into the SD card reader (which is /dev/da1 here), nothing happens. That's why: # true > /dev/da1 And suddenly: # ls /dev/da* /dev/da0 /dev/da1 /dev/da1s1 /dev/da2 Now possible: # mount /media/sd The SD card can be accessed (due to the entry in /etc/fstab which specifies the required options); in this case /dev/da1s1 will be mounted at /media/sd as msdosfs with the options set of rw,noauto,noatime,-m=644,-M=755. When done: # umount /media/sd The card is then removed. But the device file shown above (/dev/da1s1) isn't removed, even after "re-tasting" it keeps being present: # ls /dev/da* /dev/da0 /dev/da1 /dev/da1s1 /dev/da2 # true > /dev/da1 /dev/da1: Device not configured. # ls /dev/da* /dev/da0 /dev/da1 /dev/da1s1 /dev/da2 My questions so far: 1. In order to get the notification mechanism working for card readers, is it acceptable to do "true > true > /dev/da[0-2]" in a repeated manner, let's say, every 10 seconds (because users don't want to waste time waiting)? Is this better being done with a /etc/rc.local "hack" or via cron? 2. How to deal with the notification when the card disappears? 3. Does using the presence of labels (not tested here) offer a better approach? I will be thankful for any insight in this strange topic. :-) -- Polytropon Magdeburg, Germany Happy FreeBSD user since 4.0 Andra moi ennepe, Mousa, ...
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