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2011-03-10
, 04:31
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Posts: 1,746 |
Thanked: 2,100 times |
Joined on Sep 2009
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#42
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Originally Posted by Funklord
These platforms that we call smartphones are far from what is considered "embedded" these days. To reach the blurring point between "embedded" and "phone" from the industrial perspective you either step through the looking glass into the realm of the baseband (where vxworks or some other RTOS rules the day,) or drop down under 16MB of RAM into the dumbphone world where they are trying to wring every last cent out of the system.
String parsing interfaces are a big no-no on most embedded platforms since they waste memory and time
At the level we're working at, and with the hardware in these platforms, string parsing is totally trivial and you're better off working on minimizing wake-ups and overall power saving.
and how is it better than just using a shell interface?
Originally Posted by Funklord
It's unlikely you'll ever see raw NAND in that quantity. The eMMC interface simplifies system bring up so much it's ridiculous.
It may be fine for n900 and similar platforms with huge amounts of memory, (once we get rid of MMC and maybe have all that 32G as pure, directly accessible nand chips)
I believe the largest part of the phone market needs a root system measured in a few M not G.
Look at openWRT project, it's easy to configure, comes out tiny, and they developed it out of a need for a better router distro. Now every mfg and their mom is using it in at least a few of the higher end routers since it saves them money and users get a better product.
| The Following User Says Thank You to wmarone For This Useful Post: | ||
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2011-03-10
, 22:39
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Posts: 69 |
Thanked: 41 times |
Joined on Feb 2010
@ Sweden
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#43
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Originally Posted by wmarone
I like the wringing part.
These platforms that we call smartphones are far from what is considered "embedded" these days. To reach the blurring point between "embedded" and "phone" from the industrial perspective you either step through the looking glass into the realm of the baseband (where vxworks or some other RTOS rules the day,) or drop down under 16MB of RAM into the dumbphone world where they are trying to wring every last cent out of the system.
Originally Posted by wmarone
String parsing is also inherently dynamic, along with a higher likelyhood of timeouts, races and security issues.
At the level we're working at, and with the hardware in these platforms, string parsing is totally trivial and you're better off working on minimizing wake-ups and overall power saving.
Originally Posted by wmarone
Yeah, I remember when dbus first came, but I've always linked it in my mind with very high level stuff like gnome and kde. By a shell interface I mean pipes, fifo, stdio or what ever might be appropriate. For example: mplayer slave mode.
dbus is common across Linux platforms, and has its own maintenance team. I'm not quite sure what you mean by a "shell interface" though.
Originally Posted by wmarone
I'm very interested to hear more if you have insight on the issues?
It's unlikely you'll ever see raw NAND in that quantity. The eMMC interface simplifies system bring up so much it's ridiculous.
At what point? bootloader? linux?
I always thought the MTD subsystem was extremely flexible, was thinking of learning how to develop a larger flash memory bus for an arm board.
Do you know why pure nand costs more than nand+ftl?
Originally Posted by wmarone
Stuck a usb sound card and mpd in mine.. but realized I didn't really need it :P
openWRT is awesome, but with only 8MB of storage in my WNDR3700 I can't do a whole. In fact, I only have 1MB free and there's more I'd like for it to do, which will probably involve me performing acrobatics (or contortions) to make it boot from an external 8GB USB stick.
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2011-03-11
, 00:50
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Posts: 1,522 |
Thanked: 392 times |
Joined on Jul 2010
@ São Paulo, Brazil
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#44
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Regarding synchronizing contacts, even when both have been edited between synchs, i can't see the algorithm being all that complicated.
Always store both last modified date and last synch date.
If the number of each type(and subtype) of field is the same, consider changes to be editing them.
If the number is different, look for matches between the two contacts, leave the fields that match alone, the ones that aren't the same on both you treat as being added or removed (for additional advanced functionality, look for similar values between fields of the same type and of similar type (landline, cell and fax numbers, plain, work and home substypes etc) looking for potential changes and optionally ask the user whether they are the same or should be treated as seaparated)
In cases where both contacts have been changed between synchs, consider differences to be conflicts and have the user manually solve the conflicts. In case the synch dates (and times) don't match, ask the user what to do (choose on a case by case basis, use the most recent, oldest, from one source instead of other, the biggest one etc, with an additional option to remember this choice (for this session, forever or no, etc)
Did i miss anything?
Always store both last modified date and last synch date.
If the number of each type(and subtype) of field is the same, consider changes to be editing them.
If the number is different, look for matches between the two contacts, leave the fields that match alone, the ones that aren't the same on both you treat as being added or removed (for additional advanced functionality, look for similar values between fields of the same type and of similar type (landline, cell and fax numbers, plain, work and home substypes etc) looking for potential changes and optionally ask the user whether they are the same or should be treated as seaparated)
In cases where both contacts have been changed between synchs, consider differences to be conflicts and have the user manually solve the conflicts. In case the synch dates (and times) don't match, ask the user what to do (choose on a case by case basis, use the most recent, oldest, from one source instead of other, the biggest one etc, with an additional option to remember this choice (for this session, forever or no, etc)
Did i miss anything?
__________________
NOKIA N900: IT'S OVER NINE THOUSAND
How to use HotspotShield in the N900
Google Voice from outside the US + Free international calls: LEARN HOW HERE!!!
NOKIA N900: IT'S OVER NINE THOUSAND
How to use HotspotShield in the N900
Google Voice from outside the US + Free international calls: LEARN HOW HERE!!!
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2011-03-11
, 01:02
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Posts: 251 |
Thanked: 70 times |
Joined on Nov 2009
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#45
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Having truly open fork, i'd suggest moving to a different hardware. Chinese phones look promising..
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2011-03-11
, 15:43
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Posts: 69 |
Thanked: 41 times |
Joined on Feb 2010
@ Sweden
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#46
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Originally Posted by TiagoTiago
Yes, syncing is not as easy as it first looks, and all approaches have severe down sides.
Regarding synchronizing contacts, even when both have been edited between synchs, i can't see the algorithm being all that complicated.
Always store both last modified date and last synch date.
If the number of each type(and subtype) of field is the same, consider changes to be editing them.
If the number is different, look for matches between the two contacts, leave the fields that match alone, the ones that aren't the same on both you treat as being added or removed (for additional advanced functionality, look for similar values between fields of the same type and of similar type (landline, cell and fax numbers, plain, work and home substypes etc) looking for potential changes and optionally ask the user whether they are the same or should be treated as seaparated)
In cases where both contacts have been changed between synchs, consider differences to be conflicts and have the user manually solve the conflicts. In case the synch dates (and times) don't match, ask the user what to do (choose on a case by case basis, use the most recent, oldest, from one source instead of other, the biggest one etc, with an additional option to remember this choice (for this session, forever or no, etc)
Did i miss anything?
The best automatic syncing mechanisms use a lot of metadata and complicated algorithms to determine what to do when for example a field has changed on two of the directories being synced.
You have to accept that a date field is NOT reliable in a PIM application. If you rely on it solely, then you will eventually mess up users data, important data.
Last sync date metadata is a bad idea, because the sync protocol becomes a 2 dir sync per design, which also needs to be paired at the very start
We know that in the real world, most syncs are 3-5 way, and that many of them will be directories that all already contain data, but have never seen each other before.
So, merging needs to be optimised for partial, N-way syncing, and assume directories have been created separately by different people.
Each field needs to have at least a unique id and a change counter metadata. The change counter + id is the most reliable source of information for merging, it can be combined with a date metadata, so you can at least guess what to do with very complicated merges.
As I said, it's far from easy. And auto-merging that works for most people may still be wrong for a some use cases.
What most solutions are missing, is a good way for the sync protocol to interrupt the user and with a proper GUI prompt the user for a merge solution.
That's why we often lose so much data when using most of the existing sync protocols.
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2011-03-11
, 15:49
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Posts: 69 |
Thanked: 41 times |
Joined on Feb 2010
@ Sweden
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#47
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I almost forgot, a good PIM editor should always include a facility and UI to merge multiple contacts into one.
Then at least it doesn't become too much of a hassle if you accidentally get duplicates, when merging with a new dir.
Then at least it doesn't become too much of a hassle if you accidentally get duplicates, when merging with a new dir.
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2011-03-11
, 17:51
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Posts: 1,746 |
Thanked: 2,100 times |
Joined on Sep 2009
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#48
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Originally Posted by Funklord
Seriously, if they could twist them and have pennies(won,yen,yuan) fall out, they would.
I like the wringing part.
By a shell interface I mean pipes, fifo, stdio or what ever might be appropriate. For example: mplayer slave mode.
I'm very interested to hear more if you have insight on the issues?
At what point? bootloader? linux?
I always thought the MTD subsystem was extremely flexible, was thinking of learning how to develop a larger flash memory bus for an arm board.
Do you know why pure nand costs more than nand+ftl
| The Following 2 Users Say Thank You to wmarone For This Useful Post: | ||
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2011-03-11
, 23:57
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Posts: 69 |
Thanked: 41 times |
Joined on Feb 2010
@ Sweden
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#49
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Originally Posted by wmarone
I suspect they just redirect it somewhere else, probably since Qt does some of it's own argument parsing among other things, they just want you to do it "their way" instead of using printf() directly etc.
Qt applications don't compile with support for that by default IIRC (for instance, printf() will execute but nothing will appear on the console unless you change how it is built.)
Or... came to think of it, isn't your GUI always a child process of main()?
Hmm.. I should know this since I wrote the Qt logging libraries for some companies.
Originally Posted by wmarone
If they needed that level of flexibility (multicast etc), it would've been easier just to use TCP/IP directly.
I'm not sure why dbus appeared, but I'm guessing there are limitations in the methods you describe that necessitated it... can't say for sure.
Originally Posted by wmarone
So, the problem is that the MTD subsystem does not have drivers for a bus that does not yet exist, most drivers maybe assume that you've connected it to GPIOs directly?
For bootloader and kernel you have OneNAND devices (packaged with your RAM and installed on top of the SoC,) which still accept raw NAND commands. Generally, however, this is one or two devices set up in a certain fashion to act like one.
Obviously a new memory bus would need a new driver. But to make things simpler, you could just a have a tiny nor directly connected, to store the bootloader, kernel and a simple root.
Then when the kernel is up, you use the more complicated bus and filesystem, so you don't need to develop drivers for the bootloader as well.
Originally Posted by wmarone
But a block interface does not translate well to flash memory, that's why we lose so much performance and suddenly the thing may crash when there are too many faulty flash blocks.
It is quite flexible, but eMMC lets you hide all the NAND + FTL complexity behind a standard block interface and share a driver with your SD card. It also dodges the issue that a lot of filesystems geared towards raw NOR/NAND devices don't behave well on larger devices (more CPU, more RAM.)
So, is performance an issue when you scale ubifs to gigabyte sizes?
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2011-03-12
, 03:58
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Posts: 1,746 |
Thanked: 2,100 times |
Joined on Sep 2009
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#50
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Originally Posted by Funklord
I'm not quite sure what you're getting at. In any case, you can boot from NAND directly, pretty much every smartphone does it and an increasing number of basebands are. NOR, IIRC is being dumped due to its price, lack of density, and decreasing support for it in SoCs.
So, the problem is that the MTD subsystem does not have drivers for a bus that does not yet exist, most drivers maybe assume that you've connected it to GPIOs directly?
Obviously a new memory bus would need a new driver. But to make things simpler, you could just a have a tiny nor directly connected, to store the bootloader, kernel and a simple root.
Then when the kernel is up, you use the more complicated bus and filesystem, so you don't need to develop drivers for the bootloader as well.
But a block interface does not translate well to flash memory, that's why we lose so much performance and suddenly the thing may crash when there are too many faulty flash blocks.
So, is performance an issue when you scale ubifs to gigabyte sizes?
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You could have the contacts in a sqlite database with any structure provided there was an interface that produced a vcard in response to a query.
Personally, I'd like to see that interface be groupdav provided it can be made efficient enough. That way we can make synchronisation a simple affair for tasks, contacts, calendar, etc.
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