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atmel_spi: support zero length transfer

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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>
This commit is contained in:
Atsushi Nemoto 2008-04-28 02:14:19 -07:00 committed by Linus Torvalds
parent b687d2a8f8
commit 0671981478
1 changed files with 1 additions and 1 deletions
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2
drivers/spi/atmel_spi.c
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@ -616,7 +616,7 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg)
return -ESHUTDOWN; return -ESHUTDOWN;
list_for_each_entry(xfer, &msg->transfers, transfer_list) { 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"); dev_dbg(&spi->dev, "missing rx or tx buf\n");
return -EINVAL; return -EINVAL;
} }