linux-kernel - Re: [PATCH v2 1/2 RESEND] staging: dgnc: remove dead code in dgnc_tty

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Message-ID: <20150411045144.GA3496@sudip-PC>
Date:	Sat, 11 Apr 2015 10:21:44 +0530
From:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:	Giedrius Statkevičius 
	<giedrius.statkevicius@...il.com>
Cc:	lidza.louina@...il.com, markh@...pro.net,
	gregkh@...uxfoundation.org, driverdev-devel@...uxdriverproject.org,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2 RESEND] staging: dgnc: remove dead code in
 dgnc_tty_write()

On Fri, Apr 10, 2015 at 05:48:54PM +0300, Giedrius Statkevičius wrote:
> Remove the dead code protected by in_user in dgnc_tty_write() because it is set
> to 0 and never changed to 1 thus the code in ifs never gets executed.
dgnc_tty_write() is being called by dgnc_tty_put_char() and it is also
the write callback function of struct tty_operations, so I think the
correct fix will be to use from_user and make it 0 when
dgnc_tty_put_char() calls this function else make it 1 to inform the
function that the data wil be coming from the userspace. Maybe some
thing like this:

diff --git a/drivers/staging/dgnc/dgnc_tty.c b/drivers/staging/dgnc/dgnc_tty.c
index ce4187f..96eaf5b 100644
--- a/drivers/staging/dgnc/dgnc_tty.c
+++ b/drivers/staging/dgnc/dgnc_tty.c
@@ -1682,10 +1682,15 @@ static int dgnc_tty_put_char(struct tty_struct *tty, unsigned char c)
 	/*
 	 * Simply call tty_write.
 	 */
-	dgnc_tty_write(tty, &c, 1);
+	__dgnc_tty_write(tty, &c, 1, 0);
 	return 1;
 }
 
+static int dgnc_tty_write(struct tty_struct *tty,
+		const unsigned char *buf, int count)
+{
+	__dgnc_tty_write(tty, buf, count, 1);
+}
 
 /*
  * dgnc_tty_write()
@@ -1693,8 +1698,8 @@ static int dgnc_tty_put_char(struct tty_struct *tty, unsigned char c)
  * Take data from the user or kernel and send it out to the FEP.
  * In here exists all the Transparent Print magic as well.
  */
-static int dgnc_tty_write(struct tty_struct *tty,
-		const unsigned char *buf, int count)
+static int __dgnc_tty_write(struct tty_struct *tty,
+		const unsigned char *buf, int count, int from_user)
 {
 	struct channel_t *ch = NULL;
 	struct un_t *un = NULL;
@@ -1705,7 +1710,6 @@ static int dgnc_tty_write(struct tty_struct *tty,
 	ushort tail;
 	ushort tmask;
 	uint remain;
-	int from_user = 0;
 
 	if (tty == NULL || dgnc_TmpWriteBuf == NULL)
 		return 0;


regards
sudip
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