[PATCH] Input: alps - Fix a mismatch between a condition check and its comment

[PATCH] Input: alps - Fix a mismatch between a condition check and its comment

[Hui Wang]

In the function alps_is_cs19_trackpoint(), we check if the param[1] is
in the 0x20~0x2f range, but the code we wrote for this checking is not
correct:
(param[1] & 0x20) does not mean param[1] is in the range of 0x20~0x2f,
it also means the param[1] is in the range of 0x30~0x3f, 0x60~0x6f...

Now fix it with a new condition checking ((param[1] & 0xf0) == 0x20).

Fixes: 7e4935ccc323 ("Input: alps - don't handle ALPS cs19 trackpoint-only device")
Cc: stable@vger.kernel.org
Signed-off-by: Hui Wang <hui.wang@canonical.com>
---
 drivers/input/mouse/alps.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c
index 62ffea00902a..34700eda0429 100644
--- a/drivers/input/mouse/alps.c
+++ b/drivers/input/mouse/alps.c
@@ -2876,7 +2876,7 @@ static bool alps_is_cs19_trackpoint(struct psmouse *psmouse)
 	 * trackpoint-only devices have their variant_ids equal
 	 * TP_VARIANT_ALPS and their firmware_ids are in 0x20~0x2f range.
 	 */
-	return param[0] == TP_VARIANT_ALPS && (param[1] & 0x20);
+	return param[0] == TP_VARIANT_ALPS && ((param[1] & 0xf0) == 0x20);
 }
 
 static int alps_identify(struct psmouse *psmouse, struct alps_data *priv)
-- 
2.17.1

Re: [PATCH] Input: alps - Fix a mismatch between a condition check and its comment

[Dmitry Torokhov]

On Fri, Jul 19, 2019 at 05:01:35PM +0800, Hui Wang wrote:
> In the function alps_is_cs19_trackpoint(), we check if the param[1] is
> in the 0x20~0x2f range, but the code we wrote for this checking is not
> correct:
> (param[1] & 0x20) does not mean param[1] is in the range of 0x20~0x2f,
> it also means the param[1] is in the range of 0x30~0x3f, 0x60~0x6f...
> 
> Now fix it with a new condition checking ((param[1] & 0xf0) == 0x20).
> 
> Fixes: 7e4935ccc323 ("Input: alps - don't handle ALPS cs19 trackpoint-only device")
> Cc: stable@vger.kernel.org
> Signed-off-by: Hui Wang <hui.wang@canonical.com>

Applied, thank you.

> ---
>  drivers/input/mouse/alps.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c
> index 62ffea00902a..34700eda0429 100644
> --- a/drivers/input/mouse/alps.c
> +++ b/drivers/input/mouse/alps.c
> @@ -2876,7 +2876,7 @@ static bool alps_is_cs19_trackpoint(struct psmouse *psmouse)
>  	 * trackpoint-only devices have their variant_ids equal
>  	 * TP_VARIANT_ALPS and their firmware_ids are in 0x20~0x2f range.
>  	 */
> -	return param[0] == TP_VARIANT_ALPS && (param[1] & 0x20);
> +	return param[0] == TP_VARIANT_ALPS && ((param[1] & 0xf0) == 0x20);
>  }
>  
>  static int alps_identify(struct psmouse *psmouse, struct alps_data *priv)
> -- 
> 2.17.1
> 

-- 
Dmitry