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External RAM filesystem



Hi,


Aitor.Viana.Sanchez at esa.int schrieb:
> 
> Based on the example i made (see bellow) i got questions.
> 
> Basically this example allows to read/write information in the RAMDISK
> area (which is an array in the example) by means of the filesystem API
> but does not allow to create files because the open/f_open routine shall
> open the "/dev/ramdisk0" device.

what you see is that you can access the raw device. This is good, but
not sufficent :-)


> Is it possible to "mount" somehow the /dev/ramdisk0 and then, using the
> open/f_open, etc. calls to create file inside this RAMDISK?

Sure this is the overall goal!

I have search my old software dungeon and found some bits and pieces
which should lead the further way.

Obviously your raw device worls, so you now need to:
- format it to contain a proper DOSFS disk structure.

You can do this with the following call:

{
  msdos_format_request_param_t rqdata;

  memset(&rqdata,0,sizeof(rqdata);
  rqdata.OEMName="Rtems";
  rqdata.VolLabel="MyRTEMSDIsk";
  rqdata.fattype=MSDOS_FMT_FATANY;
  rqdata.quick_format=TRUE;

  msdos_format("/dev/ramdisk0",&rqdata);
}

Now the ramdisk should have a proper data format in its sectors.

The next steps are to:
- create a mount point (a directory in the IMFS that will be used as a
"hook" to the DOSFS).
- mount the ramdisk at this mount point.

You can do this either with the corresponding classic calls or use the
table-based "rtems_fsmount" function for this:
fstab_t fs_mnt_table[] = {
  {
     "/dev/ramdisk0","/mnt/ramdisk",
     &msdos_ops, RTEMS_FILESYSTEM_READ_WRITE,
     FSMOUNT_MNT_OK | FSMOUNT_MNT_CRTERR | FSMOUNT_MNT_FAILED,
     0
  }
};

rtems_fsmount(fs_mnt_table,
              sizeof(fs_mnt_table)/sizeof(fs_mnt_table[0]),
              NULL);

Then your ramdisk is accessible starting at "/mnt/ramdisk".

Please give some feedback if things work right. And don't forget the
Wiki (hint,hint!)

good luck,
Thomas.

> 
> Cheers,
> 
> Sitor
> 
> 
> Here is the example I made.
> 
> *rtems-config.h file --------------->*
> 
> #ifndef RTEMSCONFIG_H_
> #define RTEMSCONFIG_H_
> 
> /* configuration information */
> 
> rtems_task Init( rtems_task_argument argument);
> extern char ramdisk[];
> 
> #define CONFIGURE_NEEDS_CONSOLE_DRIVER
> 
> #define CONFIGURE_RTEMS_INIT_TASKS_TABLE
> 
> #define CONFIGURE_MAXIMUM_TASKS 10
> #define CONFIGURE_MAXIMUM_SEMAPHORES 10
> #define CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS 4
> 
> rtems_bdbuf_config rtems_bdbuf_configuration[] = {
>   { 512, 40, (void *) ramdisk }
> };
> int rtems_bdbuf_configuration_size = 1;
> 
> rtems_ramdisk_config rtems_ramdisk_configuration[] = {
>   {
>      512, 40, (void *) ramdisk
>   }
> };
> 
> // The sparc-rtems-gcc version 4 changes the location of the confdefs.h
> file.
> #if (__GNUC__ > 3)
> size_t rtems_ramdisk_configuration_size = 1;
> rtems_task_priority swapout_task_priority = 100;
> #else
> int rtems_ramdisk_configuration_size = 1;
> #endif
> 
> 
> #define CONFIGURE_HAS_OWN_DEVICE_DRIVER_TABLE
> rtems_driver_address_table Device_drivers[] = {
>   CONSOLE_DRIVER_TABLE_ENTRY,
>   CLOCK_DRIVER_TABLE_ENTRY,
>   RAMDISK_DRIVER_TABLE_ENTRY
> };
> #define CONFIGURE_NUMBER_OF_DRIVERS \
>   ((sizeof(Device_drivers) / sizeof(rtems_driver_address_table)))
> #define CONFIGURE_MAXIMUM_DRIVERS 10
> 
> 
> 
> #define CONFIGURE_INIT
> 
> // The sparc-rtems-gcc version 4 changes the location of the confdefs.h
> file.
> #if (__GNUC__ > 3)
> #include <rtems/confdefs.h>
> #else
> #include <confdefs.h>
> #endif
> 
> #endif /*RTEMSCONFIG_H_*/
> 
> <---------------------------------
> 
> *test.c ----------------->*
> 
> /*
>  *  Simple test program -- simplified version of sample test hello.
>  */
> 
> #include <bsp.h>
> 
> #include <stdlib.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <assert.h>
> #include <errno.h>
> 
> #include <rtems/ramdisk.h>
> #include <rtems/bdbuf.h>
> 
> char ramdisk[30*1024];
> 
> #include "rtems-config.h"
> 
> rtems_task Init(
>   rtems_task_argument ignored
> )
> {
>         FILE *fp;
>           unsigned char buffer[512];
>           unsigned char aux[512];
>           int i;
>           size_t bw;
>          
>           // Open the RAMDISKK
>           fp = fopen( "/dev/ramdisk0", "r+" );
>           assert( fp );
> 
>           for ( i=0 ; i< 512 ; i++  )
>                   buffer[i] = (unsigned char) (i + 1);
> 
>         for (i=0; i < 30 ; i++ )
>           {
>                 bw = fwrite( buffer, 512, 1, fp );
>                 assert(bw);
>           }
> 
>         assert(fseek(fp, 0, SEEK_SET) == 0);
> 
>         for (i=0; i < 20 ; i++ )
>           {
>                   memset( aux, 0, 512 );
>                   bw = fread( aux, 512, 1, fp );
>                   assert( bw == 1 );
>                   printf("%d ", i);
> 
>                   assert( !memcmp( buffer, aux, 512 ) );
>                   assert( !memcmp( (ramdisk + (i*512)), aux, 512 ) );
>           }
> 
>   exit( 0 );
> }
> 
> /* end of file */
> 
> -----------------------------
> Aitor Viana S?nchez
> 
> ESA - European Space Technology Centre (ESTEC)
> TEC-EDD - Computer and Data Systems Section
> ESA/ESTEC P.O. Box 299 / 2200AG Noordwijk ZH, The Netherlands
> Tel (+31) 71 565 6727
> Email: aitor.viana.sanchez at esa.int
> 
> Joel Sherrill <joel.sherrill at oarcorp.com> wrote on 11/14/2007 03:15:07 PM:
> 
>> I don't remember if there is an example in the source
>> tree anywhere of doing this.  If you can put together
>> something, it would be appreciated.  Just declared
>> some large byte array and use it as the RAM for the
>> purposes of an example.
> 
>> --joel
> 
>> Aitor.Viana.Sanchez at esa.int wrote:
>> >
>> > Hi Thomas,
>> >
>> > I managed to configure the RAMDISK, and also accessing it but i got
>> > couple of questions.
>> >
>> >         - I didn't use the msdos_initialize function at all and I
>> > don't know what this function does exactly and why it is needed.
>> >         - I had also to initialize the rtems_bdbuf_configuration
>> > structure and the rtems_bdbuf_configuration_size variable, but i don't
>> > know what is this structure/variable is for.
>> >         - I can access to the RAMDISK by means of
>> > fopen("/dev/ramdisk0") for instance. But this allows me to write/read
>> > in the RAMDISK area using the file API. But apparently does not allow
>> > me to create files in the RAMDISK area (which is my intention). Lets
>> > say, I want to allocate a RAMDISK area, mount it, and then access it
>> > like a filesystem.
>> >
>> > Here is my configuration file:
>> >
>> > #ifndef RTEMSCONFIG_H_
>> > #define RTEMSCONFIG_H_
>> >
>> > /* configuration information */
>> >
>> > rtems_task Init( rtems_task_argument argument);
>> >
>> > #define CONFIGURE_TEST_NEEDS_CONSOLE_DRIVER
>> >
>> > #define CONFIGURE_RTEMS_INIT_TASKS_TABLE
>> >
>> > #define CONFIGURE_MAXIMUM_TASKS 10
>> > #define CONFIGURE_MAXIMUM_SEMAPHORES 10
>> > #define CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS 4
>> >
>> > rtems_bdbuf_config rtems_bdbuf_configuration[] = {
>> >   { 512, 20, (void *) 0 }
>> > };
>> > int rtems_bdbuf_configuration_size = 1;
>> >
>> > rtems_ramdisk_config rtems_ramdisk_configuration[] = {
>> >   {
>> >      512, 20, (void *) 0
>> >   }
>> > };
>> >
>> > int rtems_ramdisk_configuration_size = 1;
>> >
>> > #define CONFIGURE_HAS_OWN_DEVICE_DRIVER_TABLE
>> > rtems_driver_address_table Device_drivers[] = {
>> >   CONSOLE_DRIVER_TABLE_ENTRY,
>> >   CLOCK_DRIVER_TABLE_ENTRY,
>> >   RAMDISK_DRIVER_TABLE_ENTRY
>> > };
>> > #define CONFIGURE_NUMBER_OF_DRIVERS \
>> >   ((sizeof(Device_drivers) / sizeof(rtems_driver_address_table)))
>> > #define CONFIGURE_MAXIMUM_DRIVERS 10
>> >
>> > #define CONFIGURE_INIT
>> >
>> > #include <confdefs.h>
>> >
>> > #endif /*RTEMSCONFIG_H_*/
>> >
>> >
>> > Cheers,
>> >
>> > Aitor
>> >
>> >
>> > -----------------------------
>> > Aitor Viana S?nchez
>> >
>> > ESA - European Space Technology Centre (ESTEC)
>> > TEC-EDD - Computer and Data Systems Section
>> > ESA/ESTEC P.O. Box 299 / 2200AG Noordwijk ZH, The Netherlands
>> > Tel (+31) 71 565 6727
>> > Email: aitor.viana.sanchez at esa.int
>> >
>> >
>> > *Thomas Doerfler <Thomas.Doerfler at embedded-brains.de>*
>> >
>> > 11/13/2007 05:47 PM
>> >
>> >
>> > To
>> >  Aitor.Viana.Sanchez at esa.int
>> > cc
>> >  rtems-users at rtems.org
>> > Subject
>> >  Re: External RAM filesystem
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> > Hi,
>> >
>> > yes, it should be possible. There still exists a ram disk driver, which
>> > performs this function, see:
>> >
>> > cpukit/libblock/src/ramdisk.c
>> >
>> > We used it for our very first tests of the FATFS. If I recall correctly,
>> > these are the steps to work with it:
>> >
>> > - define a rtems_ramdisk_config data structure (e.g. in the init module)
>> > with the fixed name "rtems_ramdisk_configuration".
>> >
>> > - you can/must define the block size, the number of blocks and location
>> > in this structure
>> >
>> > - If you add the RAMDISK_DRIVER_TABLE_ENTRY to your device driver table,
>> > it will initialize automatically when your system comes up
>> >
>> > - Or, you can initialize the ramdisk with "ramdisk_initialize".
>> >
>> > - Next, you must format the ramdisk (use msdos_format function in
>> > cpukit/libfs/src/dosfs/msdos_format.c).
>> >
>> > - Then you can mount the ramdisk as a (unpartitioned) volume with
>> > msdos_initialze().
>> >
>> > I hope I am rather acurate on these steps.
>> >
>> > It would be nice if you could give us feedback, when things work.
>> >
>> > And it would be even nicer, if you could write a wiki entry on this
>> > under www.rtems.com/wiki
>> >
>> > wkr,
>> > Thomas.
>> >
>> >
>> >
>> >
>> >
>> > Aitor.Viana.Sanchez at esa.int schrieb:
>> > >
>> > > Hi all,
>> > >
>> > >
>> > > is it possible to configure RTEMS somehow to access and external RAM
>> > > memory address where a FAT32 (for instance) file system is placed?
> Is it
>> > > possible to configure the address and size?
>> > >
>> > > Thanks in advance.
>> > >
>> > >
>> > > Aitor
>> > >
>> > >
>> > >
> ------------------------------------------------------------------------
>> > >
>> > > _______________________________________________
>> > > rtems-users mailing list
>> > > rtems-users at rtems.com
>> > > http://rtems.rtems.org/mailman/listinfo/rtems-users
>> >
>> >
>> > --
>> > --------------------------------------------
>> > embedded brains GmbH
>> > Thomas Doerfler           Obere Lagerstr. 30
>> > D-82178 Puchheim          Germany
>> > Tel. : +49-89-18 90 80 79-2
>> > Fax  : +49-89-18 90 80 79-9
>> > email: Thomas.Doerfler at embedded-brains.de
>> > PGP public key available on request
>> >
>> > Diese Nachricht ist keine gesch?ftliche Mitteilung im Sinne des EHUG.
>> > ------------------------------------------------------------------------
>> >
>> > _______________________________________________
>> > rtems-users mailing list
>> > rtems-users at rtems.com
>> > http://rtems.rtems.org/mailman/listinfo/rtems-users
>> >


-- 
--------------------------------------------
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