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atmel_spi: support zero length transfer
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>
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@ -616,7 +616,7 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg)
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return -ESHUTDOWN;
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list_for_each_entry(xfer, &msg->transfers, transfer_list) {
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if (!(xfer->tx_buf || xfer->rx_buf)) {
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if (!(xfer->tx_buf || xfer->rx_buf) && xfer->len) {
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dev_dbg(&spi->dev, "missing rx or tx buf\n");
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return -EINVAL;
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}
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