dfu: fix some issues with reads/uploads

DFU read support appears to rely upon dfu->read_medium() updating the
passed-by-reference len parameter to indicate the remaining size
available for reading.

dfu_read_medium_mmc() never does this, and the implementation of
dfu_read_medium_nand() will only work if called just once; it hard-codes
the value to the total size of the NAND device irrespective of read
offset.

I believe that overloading dfu->read_medium() is confusing. As such,
this patch introduces a new function dfu->get_medium_size() which can
be used to explicitly find out the medium size, and nothing else.
dfu_read() is modified to use this function to set the initial value for
dfu->r_left, rather than attempting to use the side-effects of
dfu->read_medium() for this purpose.

Due to this change, dfu_read() must initially set dfu->b_left to 0, since
no data has been read.

dfu_read_buffer_fill() must also be modified not to adjust dfu->r_left
when simply copying data from dfu->i_buf_start to the upload request
buffer. r_left represents the amount of data left to be read from HW.
That value is not affected by the memcpy(), but only by calls to
dfu->read_medium().

After this change, I can read from either a 4MB or 1.5MB chunk of a 4MB
eMMC boot partion with CONFIG_SYS_DFU_DATA_BUF_SIZE==1MB. Without this
change, attempting to do that would result in DFU read returning no data
at all due to r_left never being set.

Signed-off-by: Stephen Warren <swarren@nvidia.com>

1 files changed, 14 insertions, 6 deletions

diff --git a/drivers/dfu/dfu.c b/drivers/dfu/dfu.c
index dc09ff6..dab5e70 100644
--- a/drivers/dfu/dfu.c
+++ b/drivers/dfu/dfu.c
@@ -267,7 +267,6 @@ static int dfu_read_buffer_fill(struct dfu_entity *dfu, void *buf, int size)
 
 			dfu->i_buf += chunk;
 			dfu->b_left -= chunk;
-			dfu->r_left -= chunk;
 			size -= chunk;
 			buf += chunk;
 			readn += chunk;
@@ -313,10 +312,19 @@ int dfu_read(struct dfu_entity *dfu, void *buf, int size, int blk_seq_num)
 		if (dfu->i_buf_start == NULL)
 			return -ENOMEM;
 
-		ret = dfu->read_medium(dfu, 0, dfu->i_buf_start, &dfu->r_left);
-		if (ret != 0) {
-			debug("%s: failed to get r_left\n", __func__);
-			return ret;
+		dfu->r_left = dfu->get_medium_size(dfu);
+		if (dfu->r_left < 0)
+			return dfu->r_left;
+		switch (dfu->layout) {
+		case DFU_RAW_ADDR:
+		case DFU_RAM_ADDR:
+			break;
+		default:
+			if (dfu->r_left >= dfu_buf_size) {
+				printf("%s: File too big for buffer\n",
+				       __func__);
+				return -EOVERFLOW;
+			}
 		}
 
 		debug("%s: %s %ld [B]\n", __func__, dfu->name, dfu->r_left);
@@ -326,7 +334,7 @@ int dfu_read(struct dfu_entity *dfu, void *buf, int size, int blk_seq_num)
 		dfu->offset = 0;
 		dfu->i_buf_end = dfu_get_buf() + dfu_buf_size;
 		dfu->i_buf = dfu->i_buf_start;
-		dfu->b_left = min(dfu_buf_size, dfu->r_left);
+		dfu->b_left = 0;
 
 		dfu->bad_skip = 0;