Filesystem in RTEMS

Sun Oct 22 10:00:03 UTC 2017

I have mounted JFFS2 successfully, according to the return value. 
Yes, it takes some time to do the mounting work.

But, when I downloaded a file like "test.txt" into flash via FTP and restarted the system, error came up.

<5>JFFS2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x01FC0028: 0xE5DF instead
<5>JFFS2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x01FC002C: 0xE5DF instead
<5>JFFS2: Further such events for this erase block will not be printed
<5>JFFS2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x01FD0000: 0x000C instead
<5>JFFS2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x01FD0004: 0xB0B1 instead
<5>JFFS2: jffs2_scan_eraseblock(): Magic bitmask 0x1985 not found at 0x01FD0008: 0x0054 instead
<5>JFFS2: Cowardly refusing to erase blocks on filesystem with no valid JFFS2 nodes
<5>JFFS2: empty_blocks 0, bad_blocks 0, c->nr_blocks 510
mount failed.

Everything worked well, after erasing the whole flash. But errors came up without erasing it. 

Best wishes,
xuelin.tian at qkmtech.com

From: xuelin.tian
Date: 2017-10-21 22:07
To: Sebastian Huber
CC: users
Subject: Re: Filesystem in RTEMS
> There is no general purpose flash framework in RTEMS (like MTD on Linux). The JFFS2 uses therefore a framework independent interface.  You have to provide functions for the basic flash operations read, program and erase > yourself.  You should test these operations separately.
>
> The first mount of JFFS2 on a completely erased flash may take a while since it is erased block by block and then the clean markers are programmed.
> 
> http://www.linux-mtd.infradead.org/faq/jffs2.html#L_clmarker

I have already tested my flash operations, they all worked well. Now, I use the same handle (an instance based on Xilinx BSP) to access to the hardware. And I just have one little question here, what is the appropriate block size for the JFFS2? The size of page is 256B, and size of segment is either 4KB or 64KB. 

> We have a filesystem guide:
> 
> https://docs.rtems.org/branches/master/filesystem/index.html
>
> Unfortunately it is out dated and incomplete. Maybe you can help to improve it.

Sure, I am willing to do that, after fully understanding the file system in RTEMS.

------------------ Original ------------------
From:  "Sebastian Huber"<sebastian.huber at embedded-brains.de>;
Date:  Sat, Oct 21, 2017 06:52 PM
To:  "xuelin tian"<xuelin.tian at qkmtech.com>; 
Cc:  "users"<users at rtems.org>; 
Subject:  Re: Filesystem in RTEMS

----- Am 21. Okt 2017 um 2:17 schrieb xuelin tian xuelin.tian at qkmtech.com:

> I followed the example (testsuites/fstests/jffs2_support/fs_support.c), and some
> error came up, like
> "undefined reference to rtems_jffs2_initialize",
> "undefined reference to rtems_jffs2_compressor_zlib_compress", and
> "undefined reference to rtems_jffs2_compressor_zlib_decompress"
> I have no clue here. Do I have to give my own implementation of these functions
> here? I can exploit the default functions for jffs2 entry table and compress, I
> think.

In order to use JFFS2 with compression you have to add "-ljffs2 -lz" to your linker command line.

> 
> And I have a little confused about the model of device driver in rtems, since I
> get stuck for a few days.
> First, a deivce descriptor (rtems_fdisk_device_desc) should be given, including
> some handlers defined in rtems_fdisk_driver_handlers,  and device configuration
> (rtems_flashdisk_config).
> Then, I need to register (or initialize) my flash device into rtems dynamically
> or statically, with my own initialize, open, close functions.
> Last, the JFFS2 should be set up based on the registered device driver. The
> block size need to be equal to the page size of flash, and the read, write,
> erase operations should invoke the corresponding functions defined in
> rtems_fdisk_driver_handlers.
> 
> Am I correct in this whoe process?

There is no general purpose flash framework in RTEMS (like MTD on Linux). The JFFS2 uses therefore a framework independent interface.  You have to provide functions for the basic flash operations read, program and erase yourself.  You should test these operations separately.

The first mount of JFFS2 on a completely erased flash may take a while since it is erased block by block and then the clean markers are programmed.

http://www.linux-mtd.infradead.org/faq/jffs2.html#L_clmarker

We have a filesystem guide:

https://docs.rtems.org/branches/master/filesystem/index.html

Unfortunately it is out dated and incomplete. Maybe you can help to improve it.
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