From: Tony Lindgren <tony@atomide.com>
Date: Tue, 2 Jan 2007 20:25:40 +0000 (-0800)
Subject: I2C: Add back the zero size hack
X-Git-Tag: v2.6.21-omap1~187
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=f690b5406fd6b4094d06ebc9ea9ae07a5bd87f32;p=linux-2.6-omap-h63xx.git

I2C: Add back the zero size hack

This is needed to probe I2C chips until we can get the chips
from board-*.c files.

Signed-off-by: Tony Lindgren <tony@atomide.com>
---

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index da897a48c6a..a059a3adc2e 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -285,12 +285,14 @@ static int omap_i2c_xfer_msg(struct i2c_adapter *adap,
 			     struct i2c_msg *msg, int stop)
 {
 	struct omap_i2c_dev *dev = i2c_get_adapdata(adap);
+	u8 zero_byte = 0;
 	int r;
 	u16 w;
 
 	dev_dbg(dev->dev, "addr: 0x%04x, len: %d, flags: 0x%x, stop: %d\n",
 		msg->addr, msg->len, msg->flags, stop);
 
+#if 0
 	if (msg->len == 0)
 		return -EINVAL;
 
@@ -300,6 +302,27 @@ static int omap_i2c_xfer_msg(struct i2c_adapter *adap,
 	dev->buf = msg->buf;
 	dev->buf_len = msg->len;
 
+#else
+
+	omap_i2c_write_reg(dev, OMAP_I2C_SA_REG, msg->addr);
+	/* REVISIT: Remove this hack when we can get I2C chips from board-*.c
+	 *	    files
+	 * Sigh, seems we can't do zero length transactions. Thus, we
+	 * can't probe for devices w/o actually sending/receiving at least
+	 * a single byte. So we'll set count to 1 for the zero length
+	 * transaction case and hope we don't cause grief for some
+	 * arbitrary device due to random byte write/read during
+	 * probes.
+	 */
+	if (msg->len == 0) {
+		dev->buf = &zero_byte;
+		dev->buf_len = 1;
+	} else {
+		dev->buf = msg->buf;
+		dev->buf_len = msg->len;
+	}
+#endif
+
 	omap_i2c_write_reg(dev, OMAP_I2C_CNT_REG, dev->buf_len);
 
 	init_completion(&dev->cmd_complete);