Smartdevice usecase [LWN.net]

Smartdevice usecase

Posted Aug 24, 2012 8:55 UTC (Fri) by Aissen (subscriber, #59976)
Parent article: On the need for a new removable device filesystem

The article talks about how MTP is used to sidestep the "other OS not supporting filesystem X" issue. But it's not its only use.

MTP's nature allows the "gadget" (smartphone or any linux device) to still have access to the filesystem while it's being shared. The USB Mass storage model is "all or nothing": it forces the gadget to abandon everything it's doing with the partition/fs as soon as it's plugged; and then rescan everything (for safety, database updates, etc.) when unpluggued.

That is a problem that cannot be adressed with a new filesystem.

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Smartdevice usecase

Posted Aug 24, 2012 17:25 UTC (Fri) by jimparis (subscriber, #38647) [Link]

> The USB Mass storage model is "all or nothing": it forces the gadget to abandon everything it's doing with the partition/fs as soon as it's plugged; and then rescan everything (for safety, database updates, etc.) when unpluggued.

> That is a problem that cannot be adressed with a new filesystem.

Why not? The reason the gadget needs to "abandon everything" is because none of the currently-used filesystems can handle concurrent access to the underlying device at the block level. But there are filesystems that are supposed to allow that, like http://en.wikipedia.org/wiki/Global_File_System

Smartdevice usecase

Posted Aug 27, 2012 8:02 UTC (Mon) by Aissen (subscriber, #59976) [Link]

Thanks ! I didn't know about GFS2. It still has some hardware requirements that are nowhere to be found on a mobile phone.
It would be interesting to see how this tech would apply to embedded devices.

Smartdevice usecase

Posted Aug 25, 2012 14:03 UTC (Sat) by rvfh (subscriber, #31018) [Link]

The Nexus S already did not have a µSD port, because Google find them issue-prone. The Galaxy Nexus comes with 16 GB of internal flash though (and a broken GPS FWIW.)

Smartdevice usecase

Posted Aug 27, 2012 16:51 UTC (Mon) by mathstuf (subscriber, #69389) [Link]

How is the GPS broken? I use mine just fine…

Smartdevice usecase

Posted Aug 27, 2012 19:30 UTC (Mon) by dag- (subscriber, #30207) [Link]

I have found that the HSDPA/3G connection is not very reliable. I often find myself disabling and enabling "Mobile Data" because the device tells me I have an HSDPA connection but all apps/browsers consistently fail to connect. Either because the connection broke or it could not connect to the proxy (sic). And if my connection deteriorates from HSDPA to 3G, Edge or GPRS it does not make a difference. Once it fails, it will not recover.

Disabling and enabling sometimes helps. I have to say that I use the device mostly on the train and this is suboptimal at best, but my HTC Desire S nor my Nokia E71 had this issue so I do suspect the Google Nexus phone or this firmware (Jelly Bean 4.1.1) :-(

Smartdevice usecase

Posted Aug 28, 2012 15:34 UTC (Tue) by mathstuf (subscriber, #69389) [Link]

I've not seen this either. Service can degrade to 3G, but it goes back to 4G just fine. Of course, I still have ICS, so maybe JB changed something.

Smartdevice usecase

Posted Aug 28, 2012 15:52 UTC (Tue) by dag- (subscriber, #30207) [Link]

Well, to make things more interesting. Only yesterday-evening I powered down the phone to make sure I could test again today with a clean state. And today the signal icon gives _no signal_ at work the whole day, however most (if not all) apps do have Internet access. But I cannot call out, instead I get the message: "Mobile network not available."

3G or HSDPA (I don't know what it is using right now) works flawlessly ! So apparently you don't need a Mobile network for having 3G :) They should call it Networkless WAN :-D

Switching Airplain mode ON and OFF solved this weird situation.

I need to blog about this.

Smartdevice usecase

Posted Aug 28, 2012 15:57 UTC (Tue) by mathstuf (subscriber, #69389) [Link]

I also noticed that airplane mode had some weird behavior today as well (the charging cable is loose and gets knocked out and hasn't charged overnight twice now). Toggling wireless while in airplane mode still enabled wireless. ISTR that my Incredible had airplane mode as a "keep everything off" rather than "turn it off, but toggling overrides it" behavior.