On Sun, 8 Mar 2015, Dave Young wrote: > I used usb cdrom emulation to play video dvd for my daughter, but I got below > error: > > [dave@darkstar tmp]$ cat /mnt/sr1/VIDEO_TS/VTS_01_5.VOB >/dev/null > cat: /mnt/sr1/VIDEO_TS/VTS_01_5.VOB: Input/output error > [dave@darkstar tmp]$ dmesg|tail -1 > [ 3349.371857] sr1: rw=0, want=8028824, limit=4607996 > > The assumption of cdrom size is not right, we can create data dvd large then > 4G, also mkisofs can create an iso with only one blank directory, the size is > less than 300 sectors. The size limit does not make sense, thus remove them. > > Signed-off-by: Dave Young <dyoung@xxxxxxxxxx> > --- > drivers/usb/gadget/function/storage_common.c | 9 --------- > 1 file changed, 9 deletions(-) > > --- linux.orig/drivers/usb/gadget/function/storage_common.c > +++ linux/drivers/usb/gadget/function/storage_common.c > @@ -247,15 +247,6 @@ int fsg_lun_open(struct fsg_lun *curlun, > > num_sectors = size >> blkbits; /* File size in logic-block-size blocks */ > min_sectors = 1; > - if (curlun->cdrom) { > - 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); > - } > - } > if (num_sectors < min_sectors) { > LINFO(curlun, "file too small: %s\n", filename); > rc = -ETOOSMALL; NAK. This patch is wrong, for a very simple reason. You wrote: > I used usb cdrom emulation to play video dvd for my daughter and this demonstrates the error quite plainly. You can't use _CD_ emulation to imitate a _DVD_ -- they are different sorts of media. Just think of what happens when you try playing a DVD on a CD player. A more suitable approach would be to add DVD emulation to the driver. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html