atmel_spi: support zero length transfer
authorAtsushi Nemoto <anemo@mba.ocn.ne.jp>
Mon, 28 Apr 2008 09:14:19 +0000 (02:14 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Mon, 28 Apr 2008 15:58:31 +0000 (08:58 -0700)
A spi transfer with zero length is not invalid.  For example, such
transfer (len == 0 && delay_usecs != 0) can be used to achieve delay
before first CLK edge after chipselect assertion.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drivers/spi/atmel_spi.c

index 1749a27..02c8e30 100644 (file)
@@ -616,7 +616,7 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg)
                return -ESHUTDOWN;
 
        list_for_each_entry(xfer, &msg->transfers, transfer_list) {
-               if (!(xfer->tx_buf || xfer->rx_buf)) {
+               if (!(xfer->tx_buf || xfer->rx_buf) && xfer->len) {
                        dev_dbg(&spi->dev, "missing rx or tx buf\n");
                        return -EINVAL;
                }