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authorDavid Brownell <dbrownell@users.sourceforge.net>2009-04-13 22:35:03 +0000
committerChris Wright <chrisw@sous-sol.org>2009-04-27 10:37:00 -0700
commit68890fb0bae12f076377dd6a9371be0289b98b7b (patch)
tree1ed2e23d94f4431c0f740758e98f2329a3fc2d10
parentd11a29e323dfd141183cdc918e31acdff02ef450 (diff)
spi: spi_write_then_read() bugfixes
upstream commit: bdff549ebeff92b1a6952e5501caf16a6f8898c8 The "simplify spi_write_then_read()" patch included two regressions from the 2.6.27 behaviors: - The data it wrote out during the (full duplex) read side of the transfer was not zeroed. - It fails completely on half duplex hardware, such as Microwire and most "3-wire" SPI variants. So, revert that patch. A revised version should be submitted at some point, which can get the speedup on standard hardware (full duplex) without breaking on less-capable half-duplex stuff. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: <stable@kernel.org> [2.6.28.x, 2.6.29.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Chris Wright <chrisw@sous-sol.org>
-rw-r--r--drivers/spi/spi.c22
1 files changed, 14 insertions, 8 deletions
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 643908b74bc0..8eba98c8ed1e 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -658,7 +658,7 @@ int spi_write_then_read(struct spi_device *spi,
int status;
struct spi_message message;
- struct spi_transfer x;
+ struct spi_transfer x[2];
u8 *local_buf;
/* Use preallocated DMA-safe buffer. We can't avoid copying here,
@@ -669,9 +669,15 @@ int spi_write_then_read(struct spi_device *spi,
return -EINVAL;
spi_message_init(&message);
- memset(&x, 0, sizeof x);
- x.len = n_tx + n_rx;
- spi_message_add_tail(&x, &message);
+ memset(x, 0, sizeof x);
+ if (n_tx) {
+ x[0].len = n_tx;
+ spi_message_add_tail(&x[0], &message);
+ }
+ if (n_rx) {
+ x[1].len = n_rx;
+ spi_message_add_tail(&x[1], &message);
+ }
/* ... unless someone else is using the pre-allocated buffer */
if (!mutex_trylock(&lock)) {
@@ -682,15 +688,15 @@ int spi_write_then_read(struct spi_device *spi,
local_buf = buf;
memcpy(local_buf, txbuf, n_tx);
- x.tx_buf = local_buf;
- x.rx_buf = local_buf;
+ x[0].tx_buf = local_buf;
+ x[1].rx_buf = local_buf + n_tx;
/* do the i/o */
status = spi_sync(spi, &message);
if (status == 0)
- memcpy(rxbuf, x.rx_buf + n_tx, n_rx);
+ memcpy(rxbuf, x[1].rx_buf, n_rx);
- if (x.tx_buf == buf)
+ if (x[0].tx_buf == buf)
mutex_unlock(&lock);
else
kfree(local_buf);