Pen drive with SD/MMC card reader on Linux

Today, I was backing up some old data from a another laptop to a USB pen drive (SD/MMC card reader) using Ubuntu 10.10 LiveCD. This pen drive was no SD card, or else, it had only itself capacity (128 MB =P).

When I tried to mount this pen drive on my Gentoo Linux, I was getting the error:

mount: unknown device

But what ?! dmesg, udevadm and lsusb were showing me that it was there:

lsusb:

Bus 002 Device 004: ID 0bda:0103 Realtek Semiconductor Corp. USB 2.0 Card Reader

dmesg:

usb 2-2: new high speed USB device using ehci_hcd and address 4
scsi4 : usb-storage 2-2:1.0
scsi 4:0:0:0: Direct-Access     Generic  2.0 Reader   -SD 1.00 PQ: 0 ANSI: 0 CCS
sd 4:0:0:0: Attached scsi generic sg1 type 0
sd 4:0:0:0: [sdb] Attached SCSI removable disk

After looking carefully to output messages on Ubuntu 10.10 LiveCD, I realized that only the card reader was being recognized, the internal storage was not.

Well, in order to resolve this problem I had to recompile the kernel and activate the option CONFIG_SCSI_MULTI_LUN:

Device Drivers -> SCSI device support

[*] Probe all LUNs on each SCSI device

After reboot the system with my new kernel I could see the expected output message from dmesg:

usb 2-2: new high speed USB device using ehci_hcd and address 4
scsi4 : usb-storage 2-2:1.0
scsi 4:0:0:0: Direct-Access     Generic  2.0 Reader   -SD 1.00 PQ: 0 ANSI: 0 CCS
scsi 4:0:0:1: Direct-Access     Generic  2.0 Reader   -FD 1.00 PQ: 0 ANSI: 0 CCS
sd 4:0:0:0: Attached scsi generic sg1 type 0
sd 4:0:0:1: Attached scsi generic sg2 type 0
sd 4:0:0:1: [sdc] 256000 512-byte logical blocks: (131 MB/125 MiB)
sd 4:0:0:1: [sdc] Write Protect is off
sd 4:0:0:1: [sdc] Mode Sense: 03 00 00 00
sd 4:0:0:1: [sdc] Assuming drive cache: write through
sd 4:0:0:0: [sdb] Attached SCSI removable disk
sd 4:0:0:1: [sdc] Assuming drive cache: write through
    sdc:
sd 4:0:0:1: [sdc] Assuming drive cache: write through
sd 4:0:0:1: [sdc] Attached SCSI removable disk

Now, I could mount the device /dev/sdc and transfer the whole backup to my homedir.

To the curious the pen drive model with 128MB is showed bellow:

My 2 cents

Boosting your Kernel on Gentoo

Everybody knows that Gentoo is a performance-architeture-oriented Linux. You can optimize your entire system changing the compiler (gcc) flags to attend the hardware specificities.

Example: I have a Sony VAIO with Intel Core 2 Duo processor, then I can use this flags on my make.conf (I unmasked sys-devel/gcc to use gcc-4.3.3 that have native support to core2 technology)

CFLAGS="-O3 -march=core2 -pipe -fomit-frame-pointer -mfpmath=sse -mmmx -msse -msse2 -msse3 -mssse3"

Then, all binaries in your system will be optimized…but and the kernel ???

Well, when you compile the kernel it uses itself compiler flags. And how to optimize it ?

Good news to you…If you have a Intel processor and use Gentoo Linux in your machine you are a lucky man. You must know the LinuxDNA project. The idea of the project is optimize the kernel to Intel architecture using the icc (Intel Compiler).

Currently, I’m working on Gentoo ebuild to linuxdna package. You’ll have more news about it soon…

Listing Shared Memory Segments in C

In this week I had to write a little code to remove all IPC Shared Memory segments that were created by one process.

I had already done it on Linux and *BSD systems, but never on (Open)Solaris. Then, I tried to search (googling) some method to do it but without successful.

Linux and *BSD’s have a syscall named sysctl() to interface it, but sunos kernel has not.

Well, after some minutes breaking my brain, I discover a syscall easiest to use than sysctl…look the code below:

#include <stdlib.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
void show_shm (void)
{
  int i;
  int     *buf;
  uint_t  nids;
  uint_t  pnids;
  for (;;)
  {
    if (shmids(buf, nids, &pnids) != 0)
      exit(1);
    if (pnids <= nids)
      break;
    buf = realloc(buf, (nids = pnids) * sizeof (int));
  }
  for (i = 0; i < pnids; i++)
    printf ("%dn", buf[i]);
}