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UBI: Add initial support for scatter gather

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Adds a new set of functions to deal with scatter gather.
ubi_eba_read_leb_sg() will read from a LEB into a scatter gather list.
The new data structure struct ubi_sgl will be used within UBI to
hold the scatter gather list itself and metadata to have a cursor
within the list.

Signed-off-by: Richard Weinberger <richard@nod.at>
Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
This commit is contained in:
Richard Weinberger
2015-01-10 22:52:13 +01:00
parent 892abde56c
commit 9ff08979e1
4 changed files with 186 additions and 15 deletions
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55
drivers/mtd/ubi/eba.c
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@@ -479,6 +479,61 @@ out_unlock:
return err;
}
/**
* ubi_eba_read_leb_sg - read data into a scatter gather list.
* @ubi: UBI device description object
* @vol: volume description object
* @lnum: logical eraseblock number
* @sgl: UBI scatter gather list to store the read data
* @offset: offset from where to read
* @len: how many bytes to read
* @check: data CRC check flag
*
* This function works exactly like ubi_eba_read_leb(). But instead of
* storing the read data into a buffer it writes to an UBI scatter gather
* list.
*/
int ubi_eba_read_leb_sg(struct ubi_device *ubi, struct ubi_volume *vol,
struct ubi_sgl *sgl, int lnum, int offset, int len,
int check)
{
int to_read;
int ret;
struct scatterlist *sg;
for (;;) {
ubi_assert(sgl->list_pos < UBI_MAX_SG_COUNT);
sg = &sgl->sg[sgl->list_pos];
if (len < sg->length - sgl->page_pos)
to_read = len;
else
to_read = sg->length - sgl->page_pos;
ret = ubi_eba_read_leb(ubi, vol, lnum,
sg_virt(sg) + sgl->page_pos, offset,
to_read, check);
if (ret < 0)
return ret;
offset += to_read;
len -= to_read;
if (!len) {
sgl->page_pos += to_read;
if (sgl->page_pos == sg->length) {
sgl->list_pos++;
sgl->page_pos = 0;
}
break;
}
sgl->list_pos++;
sgl->page_pos = 0;
}
return ret;
}
/**
* recover_peb - recover from write failure.
* @ubi: UBI device description object