rtems_ramdisk_config on leon2

Aitor Viana aitor.viana.sanchez at esa.int
Mon Jan 28 09:53:13 CST 2008


Hi all,

I am trying to set up the filesystem capabilities under the OSAL layer over
RTEMS. Basically implementing mount, unmount and mkfs routines.
I want to have capabilities to mount external RAM disk filesystems, mapped
out from the kernel space, in an SDRAM memory placed from 0x60000000 on for
instance.

The OSAL layer gets this volume table structure:

OS_VolumeInfo_t OS_VolumeTable [NUM_TABLE_ENTRIES] =
{
    /* Dev Name  Phys Dev  Vol Type        Volatile?  Free?     IsMounted?
Volname  MountPt BlockSz */
    {"unused",   "unused", FS_BASED,        TRUE,      TRUE,     FALSE,
" ",      " ",     0        },
    {"unused",   "unused", FS_BASED,        TRUE,      TRUE,     FALSE,
" ",      " ",     0        },
    {"unused",   "unused", FS_BASED,        TRUE,      TRUE,     FALSE,
" ",      " ",     0        },
    {"unused",   "unused", FS_BASED,        TRUE,      TRUE,     FALSE,
" ",      " ",     0        }
};


and I already performed a sort of translation to RTEMS declaring this
structure hereafter:
fstab_t OS_MountTable[NUM_TABLE_ENTRIES] =
{
    {OS_VolumeTable[0].DeviceName, OS_VolumeTable[0].MountPoint, &msdos_ops,
RTEMS_FILESYSTEM_READ_WRITE, FSMOUNT_MNT_OK | FSMOUNT_MNTPNT_CRTERR |
FSMOUNT_MNT_FAILED, 0 },
    {OS_VolumeTable[1].DeviceName, OS_VolumeTable[1].MountPoint, &msdos_ops,
RTEMS_FILESYSTEM_READ_WRITE, FSMOUNT_MNT_OK | FSMOUNT_MNTPNT_CRTERR |
FSMOUNT_MNT_FAILED, 0 },
    {OS_VolumeTable[2].DeviceName, OS_VolumeTable[2].MountPoint, &msdos_ops,
RTEMS_FILESYSTEM_READ_WRITE, FSMOUNT_MNT_OK | FSMOUNT_MNTPNT_CRTERR |
FSMOUNT_MNT_FAILED, 0 },
    {OS_VolumeTable[3].DeviceName, OS_VolumeTable[3].MountPoint, &msdos_ops,
RTEMS_FILESYSTEM_READ_WRITE, FSMOUNT_MNT_OK | FSMOUNT_MNTPNT_CRTERR |
FSMOUNT_MNT_FAILED, 0 }
};


The other thing we need is the rtems_bdbuf_configure structure, is defined
as:
rtems_bdbuf_config rtems_bdbuf_configuration[] = {
    //  BlockSize BlockNum    Address
    {512,         1024,          NULL}
};

and the rtems_ramdisk_configuration structure, this is the funny one. Later
I'll detail the definition of this structure. But I would to define it like:

rtems_ramdisk_config rtems_ramdisk_configuration[NUM_TABLE_ENTRIES] = {
    //  BlockSize BlockNum    Address
    {0,         0,          0x0},
    {0,         0,          0x0},
    {0,         0,          0x0},
    {0,         0,          0x0},
};


The functions to perform the mkfs and mount actions are:

int32 OS_mkfs (char *address, char *devname,char * volname, uint32
blocksize,
               uint32 numblocks)
{
    msdos_format_request_param_t rqdata;
    int i = 0;


    // find a FREE entry in the OS_VolumeTable structure
    for ( i = 0; i < NUM_TABLE_ENTRIES; i++)
    {
        if ( OS_VolumeTable[i].FreeFlag == TRUE )
            break;
    }

    // There is no entry available in the OS_VolumeTable structure
    if ( i >= NUM_TABLE_ENTRIES )
        return OS_FS_ERROR;

    // Fill up the OS_VolumeTable entry
    strcpy(OS_VolumeTable[i].DeviceName, devname);
    strcpy(OS_VolumeTable[i].VolumeName, volname);
    strcpy(OS_VolumeTable[i].PhysDevName, "");
    rtems_ramdisk_configuration[i].block_size = blocksize;
    rtems_ramdisk_configuration[i].block_num = numblocks;
    rtems_ramdisk_configuration[i].location = (void*)address;

    // We need to format the filesystem as well
    memset(&rqdata, 0, sizeof(rqdata));
    rqdata.OEMName = "RTEMS";
    rqdata.VolLabel = volname;
    rqdata.fattype = MSDOS_FMT_FATANY;
    rqdata.quick_format = TRUE;
    if( msdos_format(OS_VolumeTable[i].DeviceName, &rqdata) < 0 )
    {
        OS_MSG_DBG("Error formating the new filesystem %s(%d) at 0x%x",
OS_VolumeTable[i].DeviceName, i, rtems_ramdisk_configuration[i].location);
        return OS_FS_ERROR;
    }

    // Modify the Free flag in order to avoid future problems
    OS_VolumeTable[i].FreeFlag = FALSE;

    OS_MSG_DBG("New filesystem %s(%d) created at 0x%x",
OS_VolumeTable[i].DeviceName, i, rtems_ramdisk_configuration[i].location);
    return OS_FS_SUCCESS;

}

int32 OS_mount (const char *devname, char* mountpoint)
{
    rtems_status_code rtems_status;
    int i;

    for ( i = 0; i < NUM_TABLE_ENTRIES; ++i)
    {
        if ( (strcmp(devname, OS_VolumeTable[i].DeviceName) == 0) &&
             (OS_VolumeTable[i].FreeFlag == FALSE) )
            break;
    }

    if ( i >= NUM_TABLE_ENTRIES )
        return OS_FS_ERROR;

    // Fill up the mount point
    strcpy(OS_VolumeTable[i].MountPoint, mountpoint);

    // now we need to create a mount point. The hook to the ramdis
filesystem.
    rtems_status = (rtems_status_code)rtems_fsmount(OS_MountTable,
            sizeof(OS_MountTable)/sizeof(OS_MountTable[i]), NULL );

    if ( rtems_status == RTEMS_SUCCESSFUL )
        return OS_FS_SUCCESS;
    else
        return OS_FS_ERROR;
}

In the OS_mkfs function, everything is filled and set up correctly, just to
leave the file-system ready to get mounted. The mount function, performs the
mounting of the file-system.

The problem is that, if I define the rtems_ramdisk_configuration like is
stated before (all the fields to 0 value), I got an error trying to format
the filesystem (in the msdos_format function), but, if I define the
rtems_ramdisk_configuration like this:

    //  BlockSize BlockNum    Address
    {512,       2048,       0x62000000},
    {0,         0,          0x0},
    {0,         0,          0x0},
    {0,         0,          0x0},

with the first entry already filled, everything goes perfect. For me looks
like RTEMS assumes that this rtems_ramdisk_configuration structure is
statically configured, and no dynamic modification can be performed. Am I
doing something wrong, or it is true that it is not possible to modify the
rtems_ramdisk_configuration structure at execution time.


I don't know whether my explanation was clear enough...

Thanks in advance,

cheers,

Aitor
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