i've tested bios usb support, so i've checked how fine different OSes boot from USB mass-storage divices. here is my linux test:
kernel 2.4.21, with compiled-in usb support (core, HID and mass-storage devices) and scsi generic support
USB-HDD device supports bulk-only & scsi commands
PC with BIOS that supports USB-booting
i've executed "rdev" to point kernel that root file system will be on /dev/sda1 (cause USB-HDD uses scsi commands, it's seen as an SCSI drive)
but when i tried to boot it i've found that kernel tries to mount root file system before is scans usb-bus for devices so it falls to panic :(
when i checked sources i've found that there is no way to delay this like it's doing when mounting floppy RAMDISK.
here is my system:
Linux version 2.4.21 ([EMAIL PROTECTED]) (gcc version 2.95.3 20010315 (release)) #4 Thu Jun 19 19:41:08 MSD 2003
Linux ejik 2.4.21 #4 Thu Jun 19 19:41:08 MSD 2003 i686 unknown
Gnu C 2.95.3 Gnu make 3.79.1 binutils 2.11.90.0.19 util-linux 2.11f mount 2.11b modutils 2.4.6 e2fsprogs 1.22 reiserfsprogs 3.x.0j pcmcia-cs 3.1.26 PPP 2.4.1 Linux C Library 2.2.3 Dynamic linker (ldd) 2.2.3 Procps 2.0.7 Net-tools 1.60 Kbd 1.06 Sh-utils 2.0 Modules Loaded nvidia vmnet vmmon 3c59x
bash-2.05# cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 1
model name : Intel(R) Pentium(R) 4 CPU 1.70GHz
stepping : 2
cpu MHz : 1716.958
cache size : 256 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
bogomips : 3420.97
bash-2.05# cat /proc/modules nvidia 1540272 10 (autoclean) vmnet 21120 9 vmmon 20000 0 (unused) 3c59x 25120 1
bash-2.05# cat /proc/ioports 0000-001f : dma1 0020-003f : pic1 0040-005f : timer 0060-006f : keyboard 0070-007f : rtc 0080-008f : dma page reg 00a0-00bf : pic2 00c0-00df : dma2 00f0-00ff : fpu 0170-0177 : ide1 01f0-01f7 : ide0 02f8-02ff : serial(auto) 0376-0376 : ide1 03c0-03df : vesafb 03f6-03f6 : ide0 03f8-03ff : serial(auto) 0cf8-0cff : PCI conf1 5000-500f : Intel Corp. 82801BA/BAM SMBus c000-c07f : 3Com Corporation 3c905C-TX/TX-M [Tornado] c000-c07f : 02:03.0 d000-d01f : Intel Corp. 82801BA/BAM USB (Hub #1) d000-d01f : usb-uhci d800-d81f : Intel Corp. 82801BA/BAM USB (Hub #2) d800-d81f : usb-uhci dc00-dcff : Intel Corp. 82801BA/BAM AC'97 Audio dc00-dcff : Intel ICH2 e000-e03f : Intel Corp. 82801BA/BAM AC'97 Audio e000-e03f : Intel ICH2 f000-f00f : Intel Corp. 82801BA IDE U100 f000-f007 : ide0 f008-f00f : ide1
bash-2.05# cat /proc/iomem
00000000-0009fbff : System RAM
0009fc00-0009ffff : reserved
000a0000-000bffff : Video RAM area
000c0000-000c7fff : Video ROM
000d0000-000d07ff : Extension ROM
000f0000-000fffff : System ROM
00100000-0ffeffff : System RAM
00100000-002df321 : Kernel code
002df322-0039c1b7 : Kernel data
0fff0000-0fff2fff : ACPI Non-volatile Storage
0fff3000-0fffffff : ACPI Tables
e0000000-e7ffffff : PCI Bus #01
e0000000-e7ffffff : nVidia Corporation NV11 [GeForce2 MX]
e0000000-e0bfffff : vesafb
e8000000-ebffffff : Intel Corp. 82845 845 (Brookdale) Chipset Host Bridge
ec000000-edffffff : PCI Bus #01
ec000000-ecffffff : nVidia Corporation NV11 [GeForce2 MX]
ef000000-ef00007f : 3Com Corporation 3c905C-TX/TX-M [Tornado]
fec00000-ffffffff : reservedbash-2.05# cat /proc/scsi/scsi Attached devices: Host: scsi0 Channel: 00 Id: 00 Lun: 00 Vendor: IC25N020 Model: ATCS04-0 Rev: CA2O Type: Direct-Access ANSI SCSI revision: 02
i've made a temporary solution- just copied a code that prints "insert floppy with ramdisk and press enter" a waits for keypress:
from function "change_floppy" in init/do_mounts.c:
struct termios termios;
char c;
int fd;
printk(KERN_NOTICE "VFS: Insert %s and press ENTER\n", buf);
fd = open("/dev/console", O_RDWR, 0);
if (fd >= 0) {
sys_ioctl(fd, TCGETS, (long)&termios);
termios.c_lflag &= ~ICANON;
sys_ioctl(fd, TCSETSF, (long)&termios);
read(fd, &c, 1);
termios.c_lflag |= ICANON;
sys_ioctl(fd, TCSETSF, (long)&termios);
close(fd);
}to function "mount_block_root" in init/do_mounts.c before "get_fs_names(fs_names)" call.
it works fine: i wait for message that kernel found USB mass-storage device and then press enter, but i think it isn't a best solution.
first u always need press a key to boot
second - if pc has only usb-keyboard connected and no pc\2 or com- user couldn't mount root fs because it waits input in /dev/console
so i think it's better to add some kind of delay before mounting root, or, imho better way, - when completing init of usb bus, first scans it and connect all devices and only after all devices were connected returns to main kernel code.
regards,
Ilia Petrov
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