[PATCH] rtlwifi: remove redundant assignment to variable k

[PATCH] rtlwifi: remove redundant assignment to variable k

[Colin King]

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;
-- 
2.20.1

Re: [PATCH] rtlwifi: remove redundant assignment to variable k

[Larry Finger]

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

Re: [PATCH] rtlwifi: remove redundant assignment to variable k

[Joe Perches]

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);
 

Re: [PATCH] rtlwifi: remove redundant assignment to variable k

[Kalle Valo]

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

-- 
https://patchwork.kernel.org/patch/10970261/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches