From: David Brownell Subject: [patch 2.6.27-rc6] spi: simplify spi_write_then_read() Date: Wed, 10 Sep 2008 10:18:01 -0700 Message-ID: <200809101018.01661.david-b@pacbell.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Vernon Sauder , spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Andrew Morton Return-path: Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: spi-devel-general-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: linux-spi.vger.kernel.org From: Vernon Sauder Modify spi_write_then_read() to use one transfer. This speeds up all callers, and is a minor code shrink. Signed-off-by: Vernon Sauder Signed-off-by: David Brownell --- drivers/spi/spi.c | 22 ++++++++-------------- 1 file changed, 8 insertions(+), 14 deletions(-) --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -660,7 +660,7 @@ int spi_write_then_read(struct spi_devic int status; struct spi_message message; - struct spi_transfer x[2]; + struct spi_transfer x; u8 *local_buf; /* Use preallocated DMA-safe buffer. We can't avoid copying here, @@ -671,15 +671,9 @@ int spi_write_then_read(struct spi_devic return -EINVAL; spi_message_init(&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); - } + memset(&x, 0, sizeof x); + x.len = n_tx + n_rx; + spi_message_add_tail(&x, &message); /* ... unless someone else is using the pre-allocated buffer */ if (!mutex_trylock(&lock)) { @@ -690,15 +684,15 @@ int spi_write_then_read(struct spi_devic local_buf = buf; memcpy(local_buf, txbuf, n_tx); - x[0].tx_buf = local_buf; - x[1].rx_buf = local_buf + n_tx; + x.tx_buf = local_buf; + x.rx_buf = local_buf; /* do the i/o */ status = spi_sync(spi, &message); if (status == 0) - memcpy(rxbuf, x[1].rx_buf, n_rx); + memcpy(rxbuf, x.rx_buf + n_tx, n_rx); - if (x[0].tx_buf == buf) + if (x.tx_buf == buf) mutex_unlock(&lock); else kfree(local_buf); ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/