/**
* write_leb - write update data.
* @ubi: UBI device description object
* @vol: volume description object
* @lnum: logical eraseblock number
* @buf: data to write
* @len: data size
* @used_ebs: how many logical eraseblocks will this volume contain (static
* volumes only)
*
* This function writes update data to corresponding logical eraseblock. In
* case of dynamic volume, this function checks if the data contains 0xFF bytes
* at the end. If yes, the 0xFF bytes are cut and not written. So if the whole
* buffer contains only 0xFF bytes, the LEB is left unmapped.
*
* The reason why we skip the trailing 0xFF bytes in case of dynamic volume is
* that we want to make sure that more data may be appended to the logical
* eraseblock in future. Indeed, writing 0xFF bytes may have side effects and
* this PEB won't be writable anymore. So if one writes the file-system image
* to the UBI volume where 0xFFs mean free space - UBI makes sure this free
* space is writable after the update.
*
* We do not do this for static volumes because they are read-only. But this
* also cannot be done because we have to store per-LEB CRC and the correct
* data length.
*
* This function returns zero in case of success and a negative error code in
* case of failure.
*/
static int write_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
void *buf, int len, int used_ebs)
{
int err;
if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
int l = ALIGN(len, ubi->min_io_size);
memset(buf + len, 0xFF, l - len);
len = ubi_calc_data_len(ubi, buf, l);
if (len == 0) {
dbg_gen("all %d bytes contain 0xFF - skip", len);
return 0;
}
err = ubi_eba_write_leb(ubi, vol, lnum, buf, 0, len);
} else {
/*
* When writing static volume, and this is the last logical
* eraseblock, the length (@len) does not have to be aligned to
* the minimal flash I/O unit. The 'ubi_eba_write_leb_st()'
* function accepts exact (unaligned) length and stores it in
* the VID header. And it takes care of proper alignment by
* padding the buffer. Here we just make sure the padding will
* contain zeros, not random trash.
*/
memset(buf + len, 0, vol->usable_leb_size - len);
err = ubi_eba_write_leb_st(ubi, vol, lnum, buf, len, used_ebs);
}
return err;
}
static int write_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
void *buf, int len, int used_ebs)
{
int err;
if (vol->vol_type == UBI_DYNAMIC_VOLUME) {
int l = ALIGN(len, ubi->min_io_size);
memset(buf + len, 0xFF, l - len);
len = ubi_calc_data_len(ubi, buf, l);
if (len == 0) {
dbg_gen("all %d bytes contain 0xFF - skip", len);
return 0;
}
err = ubi_eba_write_leb(ubi, vol, lnum, buf, 0, len,
UBI_UNKNOWN);
} else {
memset(buf + len, 0, vol->usable_leb_size - len);
err = ubi_eba_write_leb_st(ubi, vol, lnum, buf, len,
UBI_UNKNOWN, used_ebs);
}
return err;
}
