On Sat, 19 Jun 2010 04:08:02 am Ryan Harper wrote:
> Create a new attribute for virtio-blk devices that will fetch the serial number
> of the block device. This attribute can be used by udev to create disk/by-id
> symlinks for devices that don't have a UUID (filesystem) associated with them.
>
> ATA_IDENTIFY strings are special in that they can be up to 20 chars long
> and aren't required to be NULL-terminated. The buffer is also zero-padded
> meaning that if the serial is 19 chars or less that we get a NULL terminated
> string. When copying this value into a string buffer, we must be careful to
> copy up to the NULL (if it present) and only 20 if it is longer and not to
> attempt to NULL terminate; this isn't needed.
>
> Signed-off-by: Ryan Harper <ryanh@xxxxxxxxxx>
> Signed-off-by: john cooper <john.cooper@xxxxxxxxxx>
> ---
> drivers/block/virtio_blk.c | 32 ++++++++++++++++++++++++++++++++
> 1 files changed, 32 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 258bc2a..f1ef26f 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -281,6 +281,31 @@ static int index_to_minor(int index)
> return index << PART_BITS;
> }
>
> +/* Copy serial number from *s to *d. Copy operation terminates on either
> + * encountering a nul in *s or after n bytes have been copied, whichever
> + * occurs first. *d is not forcibly nul terminated. Return # of bytes copied.
> + */
> +static inline int serial_sysfs(char *d, char *s, int n)
> +{
> + char *di = d;
> +
> + while (*s && n--)
> + *d++ = *s++;
> + return d - di;
> +}
> +
> +static ssize_t virtblk_serial_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct gendisk *disk = dev_to_disk(dev);
> + char id_str[VIRTIO_BLK_ID_BYTES];
> +
> + if (IS_ERR(virtblk_get_id(disk, id_str)))
> + return 0;
0? Really? That doesn't seem very informative.
> + return serial_sysfs(buf, id_str, min(VIRTIO_BLK_ID_BYTES, PAGE_SIZE));
How about something like this:
BUILD_BUG_ON(PAGE_SIZE < VIRTIO_BLK_ID_BYTES + 1);
/* id_str is not necessarily nul-terminated! */
buf[VIRTIO_BLK_ID_BYTES] = '\0';
return virtblk_get_id(disk, buf);
Thanks,
Rusty.
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