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From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
To: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: David Brownell <david-b@pacbell.net>,
	spi-devel-general@lists.sourceforge.net,
	linux-kernel@vger.kernel.org
Subject: [PATCH] atmel_spi: support zero length transfer
Date: Thu, 21 Feb 2008 00:54:32 +0900 (JST)	[thread overview]
Message-ID: <20080221.005432.07645461.anemo@mba.ocn.ne.jp> (raw)

A spi transfer with zero length is not invalid.  Such transfer can be
used to achieve delay before first CLK edge after chipselect assertion.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
---
diff --git a/drivers/spi/atmel_spi.c b/drivers/spi/atmel_spi.c
index 293b7ca..5dff5e0 100644
--- a/drivers/spi/atmel_spi.c
+++ b/drivers/spi/atmel_spi.c
@@ -606,7 +606,7 @@ 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;
 		}

             reply	other threads:[~2008-02-20 15:54 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-20 15:54 Atsushi Nemoto [this message]
2008-02-20 17:55 ` Marc Pignat
2008-02-21  1:52   ` Atsushi Nemoto
2008-02-21  9:26     ` Marc Pignat
2008-02-21 19:23       ` David Brownell
2008-02-22  9:30         ` Marc Pignat
2008-02-22 14:15           ` Atsushi Nemoto
2008-02-22 14:28             ` [spi-devel-general] " Ned Forrester
2008-02-22 19:06               ` David Brownell
2008-02-22 19:52                 ` Ned Forrester
2008-02-22 18:58             ` David Brownell
2008-02-23  2:55           ` David Brownell
2008-02-25  8:15             ` Marc Pignat
2008-02-22 14:07         ` [spi-devel-general] " Ned Forrester
2008-02-22 19:02           ` David Brownell
2008-02-22 19:36             ` Ned Forrester
2008-02-23  2:37               ` David Brownell
2008-02-25  0:25               ` Atsushi Nemoto

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