linux-kernel - [PATCH v2] Staging: comedi: convert while loop to timeout in ni_mio

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Date:	Tue, 14 Jan 2014 13:38:46 -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 v2] Staging: comedi: convert while loop to timeout in ni_mio_common.c.

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

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

I know Mr. Abbott mentioned that he wouldn't expect clean-up patches to have to deal with this sort of thing, but I thought I'd at least give the timeout thing a try.  Feel free to disregard this and take v1 of this patch instead if you would just like the simple clean-up.  That being said, I used 10000 iterations at the suggestion of Mr. Abbott, and a short delay as well.  Let me know if these values seem incorrect.  Also, at some (but not all) locations in this file that currently use timeouts, contain a check for i == timeout, with a call to either printk or comedi_error if the operation actually times out.  Would something like that be required here?

Sorry for all of the questions, but I'm sort of new around here and I'd like to help out with more than just clean-ups and this seemed like a good opportunity to at least try!

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

 drivers/staging/comedi/drivers/ni_mio_common.c | 9 ++++++++-
 1 file changed, 8 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..05cd5ed 100644
--- a/drivers/staging/comedi/drivers/ni_mio_common.c
+++ b/drivers/staging/comedi/drivers/ni_mio_common.c
@@ -687,12 +687,19 @@ 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;
+	static const int timeout = 10000;
+	int i;

 	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 */
+		for (i = 0; i < timeout; i++) {
+			if(!(ni_readl(AIFIFO_Status_6143) & 0x10))
+				break;
+			udelay(1);
+		}
 	} else {
 		devpriv->stc_writew(dev, 1, ADC_FIFO_Clear);
 		if (board->reg_type == ni_reg_625x) {
-- 
1.8.4.2

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