rtlwifi: remove redundant assignment to variable k
diff mbox series

Message ID 20190531141412.18632-1-colin.king@canonical.com
State Accepted
Commit f0822dfc5887a2f93ac2b72cd21ab307cee4226a
Delegated to: Kalle Valo
Headers show
Series
  • rtlwifi: remove redundant assignment to variable k
Related show

Commit Message

Colin King May 31, 2019, 2:14 p.m. UTC
From: Colin Ian King <colin.king@canonical.com>

The assignment of 0 to variable k is never read once we break out of
the loop, so the assignment is redundant and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/net/wireless/realtek/rtlwifi/efuse.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

Comments

Larry Finger May 31, 2019, 5:29 p.m. UTC | #1
On 5/31/19 9:14 AM, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> The assignment of 0 to variable k is never read once we break out of
> the loop, so the assignment is redundant and can be removed.
> 
> Addresses-Coverity: ("Unused value")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>   drivers/net/wireless/realtek/rtlwifi/efuse.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtlwifi/efuse.c b/drivers/net/wireless/realtek/rtlwifi/efuse.c
> index e68340dfd980..83e5318ca04f 100644
> --- a/drivers/net/wireless/realtek/rtlwifi/efuse.c
> +++ b/drivers/net/wireless/realtek/rtlwifi/efuse.c
> @@ -117,10 +117,8 @@ u8 efuse_read_1byte(struct ieee80211_hw *hw, u16 address)
>   						 rtlpriv->cfg->
>   						 maps[EFUSE_CTRL] + 3);
>   			k++;
> -			if (k == 1000) {
> -				k = 0;
> +			if (k == 1000)
>   				break;
> -			}
>   		}
>   		data = rtl_read_byte(rtlpriv, rtlpriv->cfg->maps[EFUSE_CTRL]);
>   		return data;

Colin,

Your patch is not wrong, but it fails to address a basic deficiency of this code 
snippet - when an error is detected, there is no attempt to either fix the 
problem or report it upstream. As the data returned will be garbage if this 
condition happens, we might as well replace the "break" with "return 0xFF", as 
well as deleting the "k = 0" line. Most of the callers of efuse_read_1byte() 
ignore the returned result when bits 0 and 4 are set, thus returning all 8 bits 
is not a bad fixup.

My suspicion is that this test is in the code merely to prevent an potential 
unterminated "while" loop, and that this condition is extremely unlikely to happen.

Larry
Joe Perches May 31, 2019, 7:41 p.m. UTC | #2
On Fri, 2019-05-31 at 12:29 -0500, Larry Finger wrote:
> On 5/31/19 9:14 AM, Colin King wrote:
> > From: Colin Ian King <colin.king@canonical.com>
> > 
> > The assignment of 0 to variable k is never read once we break out of
> > the loop, so the assignment is redundant and can be removed.
> > 
> > Addresses-Coverity: ("Unused value")
> > Signed-off-by: Colin Ian King <colin.king@canonical.com>
> > ---
> >   drivers/net/wireless/realtek/rtlwifi/efuse.c | 4 +---
> >   1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/drivers/net/wireless/realtek/rtlwifi/efuse.c b/drivers/net/wireless/realtek/rtlwifi/efuse.c
> > index e68340dfd980..83e5318ca04f 100644
> > --- a/drivers/net/wireless/realtek/rtlwifi/efuse.c
> > +++ b/drivers/net/wireless/realtek/rtlwifi/efuse.c
> > @@ -117,10 +117,8 @@ u8 efuse_read_1byte(struct ieee80211_hw *hw, u16 address)
> >   						 rtlpriv->cfg->
> >   						 maps[EFUSE_CTRL] + 3);
> >   			k++;
> > -			if (k == 1000) {
> > -				k = 0;
> > +			if (k == 1000)
> >   				break;
> > -			}
> >   		}
> >   		data = rtl_read_byte(rtlpriv, rtlpriv->cfg->maps[EFUSE_CTRL]);
> >   		return data;
> 
> Colin,
> 
> Your patch is not wrong, but it fails to address a basic deficiency of this code 
> snippet - when an error is detected, there is no attempt to either fix the 
> problem or report it upstream. As the data returned will be garbage if this 
> condition happens, we might as well replace the "break" with "return 0xFF", as 
> well as deleting the "k = 0" line. Most of the callers of efuse_read_1byte() 
> ignore the returned result when bits 0 and 4 are set, thus returning all 8 bits 
> is not a bad fixup.
> 
> My suspicion is that this test is in the code merely to prevent an potential 
> unterminated "while" loop, and that this condition is extremely unlikely to happen.
> 
> Larry

The function is also overly verbose with many
unnecessary rtlpriv->cfg->maps dereferences.

I'd've written it more like:
---
 drivers/net/wireless/realtek/rtlwifi/efuse.c | 57 +++++++++++-----------------
 1 file changed, 22 insertions(+), 35 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtlwifi/efuse.c b/drivers/net/wireless/realtek/rtlwifi/efuse.c
index e68340dfd980..db253f45e87d 100644
--- a/drivers/net/wireless/realtek/rtlwifi/efuse.c
+++ b/drivers/net/wireless/realtek/rtlwifi/efuse.c
@@ -87,46 +87,33 @@ void efuse_initialize(struct ieee80211_hw *hw)
 u8 efuse_read_1byte(struct ieee80211_hw *hw, u16 address)
 {
 	struct rtl_priv *rtlpriv = rtl_priv(hw);
-	u8 data;
 	u8 bytetemp;
 	u8 temp;
-	u32 k = 0;
-	const u32 efuse_len =
-		rtlpriv->cfg->maps[EFUSE_REAL_CONTENT_SIZE];
-
-	if (address < efuse_len) {
-		temp = address & 0xFF;
-		rtl_write_byte(rtlpriv, rtlpriv->cfg->maps[EFUSE_CTRL] + 1,
-			       temp);
-		bytetemp = rtl_read_byte(rtlpriv,
-					 rtlpriv->cfg->maps[EFUSE_CTRL] + 2);
-		temp = ((address >> 8) & 0x03) | (bytetemp & 0xFC);
-		rtl_write_byte(rtlpriv, rtlpriv->cfg->maps[EFUSE_CTRL] + 2,
-			       temp);
-
-		bytetemp = rtl_read_byte(rtlpriv,
-					 rtlpriv->cfg->maps[EFUSE_CTRL] + 3);
-		temp = bytetemp & 0x7F;
-		rtl_write_byte(rtlpriv, rtlpriv->cfg->maps[EFUSE_CTRL] + 3,
-			       temp);
+	int k = 0;
+	u32 *maps = rtlpriv->cfg->maps;
+	const u32 efuse_len = maps[EFUSE_REAL_CONTENT_SIZE];
 
-		bytetemp = rtl_read_byte(rtlpriv,
-					 rtlpriv->cfg->maps[EFUSE_CTRL] + 3);
-		while (!(bytetemp & 0x80)) {
-			bytetemp = rtl_read_byte(rtlpriv,
-						 rtlpriv->cfg->
-						 maps[EFUSE_CTRL] + 3);
-			k++;
-			if (k == 1000) {
-				k = 0;
-				break;
-			}
-		}
-		data = rtl_read_byte(rtlpriv, rtlpriv->cfg->maps[EFUSE_CTRL]);
-		return data;
-	} else
+	if (address >= efuse_len)
 		return 0xFF;
 
+	temp = address & 0xFF;
+	rtl_write_byte(rtlpriv, maps[EFUSE_CTRL] + 1, temp);
+	bytetemp = rtl_read_byte(rtlpriv, maps[EFUSE_CTRL] + 2);
+	temp = ((address >> 8) & 0x03) | (bytetemp & 0xFC);
+	rtl_write_byte(rtlpriv, maps[EFUSE_CTRL] + 2, temp);
+
+	bytetemp = rtl_read_byte(rtlpriv, maps[EFUSE_CTRL] + 3);
+	temp = bytetemp & 0x7F;
+	rtl_write_byte(rtlpriv, maps[EFUSE_CTRL] + 3, temp);
+
+	bytetemp = rtl_read_byte(rtlpriv, maps[EFUSE_CTRL] + 3);
+	while (!(bytetemp & 0x80)) {
+		bytetemp = rtl_read_byte(rtlpriv, maps[EFUSE_CTRL] + 3);
+		if (++k >= 1000)
+			return 0xFF;	/* Likely defect */
+	}
+
+	return rtl_read_byte(rtlpriv, maps[EFUSE_CTRL]);
 }
 EXPORT_SYMBOL(efuse_read_1byte);
Kalle Valo June 25, 2019, 5 a.m. UTC | #3
Colin King <colin.king@canonical.com> wrote:

> From: Colin Ian King <colin.king@canonical.com>
> 
> The assignment of 0 to variable k is never read once we break out of
> the loop, so the assignment is redundant and can be removed.
> 
> Addresses-Coverity: ("Unused value")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>

Patch applied to wireless-drivers-next.git, thanks.

f0822dfc5887 rtlwifi: remove redundant assignment to variable k

Patch
diff mbox series

diff --git a/drivers/net/wireless/realtek/rtlwifi/efuse.c b/drivers/net/wireless/realtek/rtlwifi/efuse.c
index e68340dfd980..83e5318ca04f 100644
--- a/drivers/net/wireless/realtek/rtlwifi/efuse.c
+++ b/drivers/net/wireless/realtek/rtlwifi/efuse.c
@@ -117,10 +117,8 @@  u8 efuse_read_1byte(struct ieee80211_hw *hw, u16 address)
 						 rtlpriv->cfg->
 						 maps[EFUSE_CTRL] + 3);
 			k++;
-			if (k == 1000) {
-				k = 0;
+			if (k == 1000)
 				break;
-			}
 		}
 		data = rtl_read_byte(rtlpriv, rtlpriv->cfg->maps[EFUSE_CTRL]);
 		return data;