linux-kernel - Re: [PATCH] Input: i8042 - i8042_flush fix for a full 8042 buffer

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Date:	Wed, 18 Sep 2013 07:44:22 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Andrey Moiseev <o2g.org.ru@...il.com>
Cc:	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: i8042 - i8042_flush fix for a full 8042 buffer

Hi Andrey,

On Wed, Sep 18, 2013 at 04:35:56PM +0400, Andrey Moiseev wrote:
> When 8042 internal data buffer is full, the driver
> erroneously decides that the controller is not present.
> 
> I've already sent this 2 weeks ago, but that message received no comments.
> 

Sorry about the delay. How about we rework it a bit and make flush
return success/error instead of number of bytes read, like in the patch
below?

Thanks.

-- 
Dmitry

Input: i8042 - i8042_flush fix for a full 8042 buffer

From: Andrey Moiseev <o2g.org.ru@...il.com>

When 8042 internal data buffer is full, the driver
erroneously decides that the controller is not present.

i8042_flush returns the number of flushed bytes, which is
in 0 - I8042_BUFFER_SIZE range inclusive. Therefore, i8042_flush
has no way to indicate an error. Moreover i8042_controller_check
takes initially full buffer (i8042_flush returned
I8042_BUFFER_SIZE) as a sign of absence of the controller.

Let's change i8042 to return success/error instead and make sure
we do not return error prematurely.

Signed-off-by: Andrey Moiseev <o2g.org.ru@...il.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---
 drivers/input/serio/i8042.c |   23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/input/serio/i8042.c b/drivers/input/serio/i8042.c
index 78e4de4..52c9ebf 100644
--- a/drivers/input/serio/i8042.c
+++ b/drivers/input/serio/i8042.c
@@ -223,21 +223,26 @@ static int i8042_flush(void)
 {
 	unsigned long flags;
 	unsigned char data, str;
-	int i = 0;
+	int count = 0;
+	int retval = 0;
 
 	spin_lock_irqsave(&i8042_lock, flags);
 
-	while (((str = i8042_read_status()) & I8042_STR_OBF) && (i < I8042_BUFFER_SIZE)) {
-		udelay(50);
-		data = i8042_read_data();
-		i++;
-		dbg("%02x <- i8042 (flush, %s)\n",
-		    data, str & I8042_STR_AUXDATA ? "aux" : "kbd");
+	while ((str = i8042_read_status()) & I8042_STR_OBF) {
+		if (count++ < I8042_BUFFER_SIZE) {
+			udelay(50);
+			data = i8042_read_data();
+			dbg("%02x <- i8042 (flush, %s)\n",
+			    data, str & I8042_STR_AUXDATA ? "aux" : "kbd");
+		} else {
+			retval = -EIO;
+			break;
+		}
 	}
 
 	spin_unlock_irqrestore(&i8042_lock, flags);
 
-	return i;
+	return retval;
 }
 
 /*
@@ -849,7 +854,7 @@ static int __init i8042_check_aux(void)
 
 static int i8042_controller_check(void)
 {
-	if (i8042_flush() == I8042_BUFFER_SIZE) {
+	if (i8042_flush()) {
 		pr_err("No controller found\n");
 		return -ENODEV;
 	}

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