linux-kernel - [PATCH v3] Staging: comedi: convert while loop to timeout in ni_mio

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Date:	Tue, 14 Jan 2014 15:31:01 -0600
From:	Chase Southwood <chase.southwood@...oo.com>
To:	gregkh@...uxfoundation.org
Cc:	abbotti@....co.uk, hsweeten@...ionengravers.com,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	Chase Southwood <chase.southwood@...oo.com>
Subject: [PATCH v3] Staging: comedi: convert while loop to timeout in ni_mio_common.c

This patch to ni_mio_common.c changes a simple while loop to a timeout,
which is preferred.

Signed-off-by: Chase Southwood <chase.southwood@...oo.com>
---

I removed the extra counter variable this time.  Greg, you mentioned that I could just look at the time that has expired to far, and exit and error out if that exceeds a limit.  Right now I'm just tracking how many times udelay is called, since that seems to conform more to other timeouts in this file, but did you instead want me to use some time function to keep track of actual real time that expires?

Thanks,
Chase Southwood

2: Changed from simple clean-up to swapping a timeout in for a while loop.

3: Removed extra counter variable, and added error checking.

 drivers/staging/comedi/drivers/ni_mio_common.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/comedi/drivers/ni_mio_common.c b/drivers/staging/comedi/drivers/ni_mio_common.c
index 457b884..143b8b8 100644
--- a/drivers/staging/comedi/drivers/ni_mio_common.c
+++ b/drivers/staging/comedi/drivers/ni_mio_common.c
@@ -687,12 +687,21 @@ static void ni_clear_ai_fifo(struct comedi_device *dev)
 {
 	const struct ni_board_struct *board = comedi_board(dev);
 	struct ni_private *devpriv = dev->private;
+	int timeout = 0;
 
 	if (board->reg_type == ni_reg_6143) {
 		/*  Flush the 6143 data FIFO */
 		ni_writel(0x10, AIFIFO_Control_6143);	/*  Flush fifo */
 		ni_writel(0x00, AIFIFO_Control_6143);	/*  Flush fifo */
-		while (ni_readl(AIFIFO_Status_6143) & 0x10) ;	/*  Wait for complete */
+		/*  Wait for complete */
+		while (timeout < 10000) {
+			if (!(ni_readl(AIFIFO_Status_6143) & 0x10))
+				break;
+			udelay(1);
+			timeout++;
+		}
+		if (timeout == 10000)
+			comedi_error(dev, "FIFO flush timeout.");
 	} else {
 		devpriv->stc_writew(dev, 1, ADC_FIFO_Clear);
 		if (board->reg_type == ni_reg_625x) {
-- 
1.8.4.2

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