diff options
| author | David Brownell <dbrownell@users.sourceforge.net> | 2009-04-13 14:39:57 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-04-13 15:04:30 -0700 |
| commit | bdff549ebeff92b1a6952e5501caf16a6f8898c8 (patch) | |
| tree | 3cebe8c0f7b26433e42832a6feb50fd6e4de75b7 /drivers/spi | |
| parent | 0769c2981495c3d05429840d6fc7a1b5e26accaa (diff) | |
spi: spi_write_then_read() bugfixes
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>
Diffstat (limited to 'drivers/spi')
| -rw-r--r-- | drivers/spi/spi.c | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 643908b74bc..8eba98c8ed1 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); |