+linux-usb On Wed, Dec 16, 2009 at 8:51 AM, Clemens Fruhwirth <clemens@xxxxxxxxxxxxx> wrote: > On Thu, Oct 15, 2009 at 1:29 AM, Grant Grundler <grundler@xxxxxxxxxx> wrote: >> On Wed, Oct 14, 2009 at 2:13 PM, Clemens Fruhwirth >> <clemens@xxxxxxxxxxxxx> wrote: >>> Short: Attached is an incomplete patch that allows user space to force >>> the capacity of an scsi device to a specific value. Any not over >>> my-dead-body objections with that? >> >> No major objection - just the usual nits: >> Why not make /sys/block/sdX/size writeable? >> (instead of adding an ioctl()) > > Oh, I like that. Sorry it took me so long to reply. It turned out that > this is a much better idea. The value that is printed when reading the > size attribute is to the value that I set in my patch indirectly > through set_capacity. So, making size writable replaces that totally. > > Patch attached. The code looks fine to me. From a process point of view, you just need to repost the patch according Documentation/SubmittingPatches . James will take attachments if you can't inline, but definitely want a concise commit log entry and Signed-off-by: line. Please also add "Reviewed-by: Grant Grundler <grundler@xxxxxxxxxx>". However, I'm suspect the is problem is really with how the block size is being reported and that bit of this puzzle isn't entirely explained yet. >> After reading the wiki page[1], my impression is that the block size >> gets reported wrong and thus the total capacity is miscalculated for >> 1GB-4GB SD cards with 1024 or 2048 byte blocks. Two questions around this: >> a) Does the host need to know the correct block size for correct operation? > > From experiments it does not look like that's the case. This is > surprising though, as one would suspect the card not to function > properly otherwise. Frankly speaking, I have not looked down the > calling chain, especially how usb-storage treats these blocks, but I'd > say not at all. Seems like the USB reader, I have, just doesn't get > the capacity right, by not considering BLOCK_LEN > 512. Can you run USBMON (see Documentation/usb/usbmon.txt) to capture the initialization sequence and post that to linux-usb? (CC'd already) >> b) Do the devices report which SD Card Association spec they are compliant >> with in the USB headers? >> >> I'm asking (b) to start the conversation about if it's feasible to >> auto-detect this in the kernel and spare all the distro's from having >> to frob the device size. >> >> If we can autodetect this case, *and* the device has a valid FAT >> partition, it should be trivial >> to use the FAT partition info instead of what the USB card reader is >> reporting. Partitioning >> a new card will probably still need "size" to be writable. > > I'm sorry, I can't really answer (b). I can't either. But if you post the usbmon output to linux-usb, I suspect someone else can. > Autofixing this doesn't seem possible to me (except for the partition > trick) as the capacity = BLOCK_LEN * BLOCKS. If BLOCK_LEN isn't > detected correctly, we can't distinguish a 1GB from 2GB card. Agreed. That's why I'm thinking getting BLOCK_LEN right is more important than hacking the resulting partition size. I'd be surprised if this conversation hasn't already occurred on linux-usb mailing list. thanks, grant ps I've cut/pasted the patch you attached below so linux-usb can see it. > Best Regards, > -- > Fruhwirth Clemens http://clemens.endorphin.org > --- linux-2.6.32/block/genhd.c 2009-12-03 04:51:21.000000000 +0100 +++ linux-2.6.32-patched/block/genhd.c 2009-12-15 08:49:31.608959038 +0100 @@ -865,7 +865,7 @@ static DEVICE_ATTR(ext_range, S_IRUGO, disk_ext_range_show, NULL); static DEVICE_ATTR(removable, S_IRUGO, disk_removable_show, NULL); static DEVICE_ATTR(ro, S_IRUGO, disk_ro_show, NULL); -static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL); +static DEVICE_ATTR(size, S_IRUGO | S_IWUSR, part_size_show, part_size_set); static DEVICE_ATTR(alignment_offset, S_IRUGO, disk_alignment_offset_show, NULL); static DEVICE_ATTR(capability, S_IRUGO, disk_capability_show, NULL); static DEVICE_ATTR(stat, S_IRUGO, part_stat_show, NULL); --- linux-2.6.32/fs/partitions/check.c 2009-12-03 04:51:21.000000000 +0100 +++ linux-2.6.32-patched/fs/partitions/check.c 2009-12-15 08:49:01.063465819 +0100 @@ -219,6 +219,19 @@ return sprintf(buf, "%llu\n",(unsigned long long)p->nr_sects); } +ssize_t part_size_set(struct device *dev, + struct device_attribute *attr, char *buf, size_t len) +{ + struct hd_struct *p = dev_to_part(dev); + char *endp; + unsigned long long val = simple_strtoull(buf, &endp, 10); + if (endp == buf) + return -EINVAL; + + p->nr_sects = val; + return len; +} + ssize_t part_alignment_offset_show(struct device *dev, struct device_attribute *attr, char *buf) { --- linux-2.6.32/include/linux/genhd.h 2009-12-03 04:51:21.000000000 +0100 +++ linux-2.6.32-patched/include/linux/genhd.h 2009-12-15 09:18:44.793088778 +0100 @@ -549,6 +549,8 @@ extern ssize_t part_size_show(struct device *dev, struct device_attribute *attr, char *buf); +extern ssize_t part_size_set(struct device *dev, + struct device_attribute *attr, char *buf, size_t len); extern ssize_t part_stat_show(struct device *dev, struct device_attribute *attr, char *buf); extern ssize_t part_inflight_show(struct device *dev, -- 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
