On Sat, 5 Dec 2009 15:34:07 -0500 (EST)
Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> > The following patch solves the problem for the BIOS. I am able to load
> > a kernel and an initrd with it correctly. Of course, it breaks everything
> > else but it can be considered as a proof of concept. I can boot from my
> > my g_file_storage cdrom drive with it on that thinkpad X31, on a mainboard with award
> > bios (with an AMD Geode 1700+ on it) and also on an INTEL D945GCLF board.
>
> No, this isn't a good approach. A better fix would be to change the
> byte mask in do_scsi_command()'s SC_READ_TOC case. In the fourth
> argument to check_command(), change (7<<6) to (0xf<<6). It's hard to
> know whether this will fix the incorrect block size, though.
>
The X31 BIOS issues the READ_TOC command several times,
if it failes, no further attempts are made to boot from cd.
> But that's just a workaround. The fact is, the BIOS is sending
> incorrect data. The same is true with the 12-byte READ(10) command,
> although here g_file_storage accepts the bad length with only a
> warning.
>
Of course, it is a workaround.
With my first patch, which should break everything which cares about
the actual sector size (since I'm using 2048 only in the READ(x) command
but not in the READ_CAPACITY) but there seems to be no BIOS
using the sector size from the READ_CAPACITY command. Linux does honor
it and does not work with my patched g_file_storage.
I cleaned up the patch especially the sector size stuff and with that patch
I have installed ubuntu from a g_file_storage_gadget in cdrom mode successfully.
diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
index b10fa31..52815d9 100644
--- a/drivers/usb/gadget/file_storage.c
+++ b/drivers/usb/gadget/file_storage.c
@@ -1599,13 +1599,17 @@ static int do_read(struct fsg_dev *fsg)
curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
return -EINVAL;
}
- file_offset = ((loff_t) lba) << 9;
+ if (mod_data.cdrom)
+ file_offset = ((loff_t) lba) << 11;
+ else
+ file_offset = ((loff_t) lba) << 9;
/* Carry out the file reads */
amount_left = fsg->data_size_from_cmnd;
if (unlikely(amount_left == 0))
return -EIO; // No default reply
-
+ if (mod_data.cdrom)
+ amount_left <<=2;
for (;;) {
/* Figure out how much we need to read:
@@ -2121,7 +2125,7 @@ static int do_read_capacity(struct fsg_dev *fsg, struct fsg_buffhd *bh)
}
put_be32(&buf[0], curlun->num_sectors - 1); // Max logical block
- put_be32(&buf[4], 512); // Block length
+ put_be32(&buf[4], mod_data.cdrom ? 2048 : 512); // Block length
return 8;
}
@@ -2130,7 +2134,6 @@ static void store_cdrom_address(u8 *dest, int msf, u32 addr)
{
if (msf) {
/* Convert to Minutes-Seconds-Frames */
- addr >>= 2; /* Convert to 2048-byte frames */
addr += 2*75; /* Lead-in occupies 2 seconds */
dest[3] = addr % 75; /* Frames */
addr /= 75;
@@ -2357,7 +2360,7 @@ static int do_read_format_capacities(struct fsg_dev *fsg,
buf += 4;
put_be32(&buf[0], curlun->num_sectors); // Number of blocks
- put_be32(&buf[4], 512); // Block length
+ put_be32(&buf[4], mod_data.cdrom ? 2048 : 512); // Block length
buf[4] = 0x02; // Current capacity
return 12;
}
@@ -2817,7 +2820,9 @@ static int check_command(struct fsg_dev *fsg, int cmnd_size,
return -EINVAL;
}
- /* Check that only command bytes listed in the mask are non-zero */
+ /* Check that only command bytes listed in the mask are non-zero
+ * Some BIOSes put some non-zero values in READ_TOC requests in
+ * the last two bytes */
fsg->cmnd[1] &= 0x1f; // Mask away the LUN
for (i = 1; i < cmnd_size; ++i) {
if (fsg->cmnd[i] && !(mask & (1 << i))) {
@@ -2957,7 +2962,7 @@ static int do_scsi_command(struct fsg_dev *fsg)
goto unknown_cmnd;
fsg->data_size_from_cmnd = get_be16(&fsg->cmnd[7]);
if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
- (7<<6) | (1<<1), 1,
+ (0xf<<6) | (1<<1), 1,
"READ TOC")) == 0)
reply = do_read_toc(fsg, bh);
break;
@@ -3660,10 +3665,10 @@ static int open_backing_file(struct lun *curlun, const char *filename)
num_sectors = size >> 9; // File size in 512-byte blocks
min_sectors = 1;
if (mod_data.cdrom) {
- num_sectors &= ~3; // Reduce to a multiple of 2048
- min_sectors = 300*4; // Smallest track is 300 frames
- if (num_sectors >= 256*60*75*4) {
- num_sectors = (256*60*75 - 1) * 4;
+ num_sectors >>= 2; // Reduce to a multiple of 2048
+ min_sectors = 300; // Smallest track is 300 frames
+ if (num_sectors >= 256*60*75) {
+ num_sectors = (256*60*75 - 1);
LINFO(curlun, "file too big: %s\n", filename);
LINFO(curlun, "using only first %d blocks\n",
(int) num_sectors);
Greetings
Andreas Kemnade
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