Re: [PATCH v4] Input: mousedev - fix implicit conversion warning
From: Dmitry Torokhov
Date: Sun Jun 25 2017 - 14:06:28 EST
Hi Nick,
On Mon, May 29, 2017 at 10:41:51PM -0700, Nick Desaulniers wrote:
> Clang warns:
>
> drivers/input/mousedev.c:653:63: error: implicit conversion from 'int'
> to 'signed char' changes value from 200 to -56
> [-Wconstant-conversion]
> client->ps2[1] = 0x60; client->ps2[2] = 3; client->ps2[3] = 200;
> ~ ^~~
>
> As far as I can tell, from
>
> http://www.computer-engineering.org/ps2mouse/
>
> Under "Command Set" > "0xE9 (Status Request)"
>
> the value 200 is a valid sample rate. Using unsigned char [], rather than
> signed char [], for client->ps2 silences this warning.
>
> Also moves some reused logic into a helper function.
>
> Signed-off-by: Nick Desaulniers <nick.desaulniers@xxxxxxxxx>
> ---
> What's new in v4:
> * replace mousedev_limit_delta() with update_clamped() that also updates
> the ps2_data and delta values. The use of the temporary val should
> avoid integral conversion and promotion issues.
>
> drivers/input/mousedev.c | 23 +++++++++++------------
> 1 file changed, 11 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/input/mousedev.c b/drivers/input/mousedev.c
> index 0e0ff84088fd..e645b8c6f2cb 100644
> --- a/drivers/input/mousedev.c
> +++ b/drivers/input/mousedev.c
> @@ -103,7 +103,7 @@ struct mousedev_client {
> spinlock_t packet_lock;
> int pos_x, pos_y;
>
> - signed char ps2[6];
> + unsigned char ps2[6];
> unsigned char ready, buffer, bufsiz;
> unsigned char imexseq, impsseq;
> enum mousedev_emul mode;
> @@ -571,27 +571,27 @@ static int mousedev_open(struct inode *inode, struct file *file)
> return error;
> }
>
> -static inline int mousedev_limit_delta(int delta, int limit)
> +static inline void
> +update_clamped(unsigned char *ps2_data, int *delta, int limit)
> {
> - return delta > limit ? limit : (delta < -limit ? -limit : delta);
> + int val = *delta > limit ? limit : (*delta < -limit ? -limit : *delta);
> + *ps2_data = (unsigned char) val;
> + *delta -= val;
Since the time the code was written we got nice helpers to clamp the
values. Does the following work for you or it still leaves clang
unhappy?
Thanks.
--
Dmitry
Input: mousedev - fix implicit conversion warning
From: Nick Desaulniers <nick.desaulniers@xxxxxxxxx>
Clang warns:
drivers/input/mousedev.c:653:63: error: implicit conversion from 'int'
to 'signed char' changes value from 200 to -56
[-Wconstant-conversion]
client->ps2[1] = 0x60; client->ps2[2] = 3; client->ps2[3] = 200;
~ ^~~
As the PS2 data is really a stream of bytes, let's switch to using u8 type
for it, which silences this warning.
Signed-off-by: Nick Desaulniers <nick.desaulniers@xxxxxxxxx>
Patchwork-Id: 9753771
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
---
drivers/input/mousedev.c | 60 +++++++++++++++++++++++++---------------------
1 file changed, 32 insertions(+), 28 deletions(-)
diff --git a/drivers/input/mousedev.c b/drivers/input/mousedev.c
index 0e0ff84088fd..6ef0c5314f69 100644
--- a/drivers/input/mousedev.c
+++ b/drivers/input/mousedev.c
@@ -15,6 +15,7 @@
#define MOUSEDEV_MINORS 31
#define MOUSEDEV_MIX 63
+#include <linux/bitops.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/poll.h>
@@ -103,7 +104,7 @@ struct mousedev_client {
spinlock_t packet_lock;
int pos_x, pos_y;
- signed char ps2[6];
+ u8 ps2[6];
unsigned char ready, buffer, bufsiz;
unsigned char imexseq, impsseq;
enum mousedev_emul mode;
@@ -291,11 +292,10 @@ static void mousedev_notify_readers(struct mousedev *mousedev,
}
client->pos_x += packet->dx;
- client->pos_x = client->pos_x < 0 ?
- 0 : (client->pos_x >= xres ? xres : client->pos_x);
+ client->pos_x = clamp_val(client->pos_x, 0, xres);
+
client->pos_y += packet->dy;
- client->pos_y = client->pos_y < 0 ?
- 0 : (client->pos_y >= yres ? yres : client->pos_y);
+ client->pos_y = clamp_val(client->pos_y, 0, yres);
p->dx += packet->dx;
p->dy += packet->dy;
@@ -571,44 +571,48 @@ static int mousedev_open(struct inode *inode, struct file *file)
return error;
}
-static inline int mousedev_limit_delta(int delta, int limit)
-{
- return delta > limit ? limit : (delta < -limit ? -limit : delta);
-}
-
-static void mousedev_packet(struct mousedev_client *client,
- signed char *ps2_data)
+static void mousedev_packet(struct mousedev_client *client, u8 *ps2_data)
{
struct mousedev_motion *p = &client->packets[client->tail];
+ s8 dx, dy, dz;
+
+ dx = clamp_val(p->dx, -127, 127);
+ p->dx -= dx;
+
+ dy = clamp_val(p->dy, -127, 127);
+ p->dy -= dy;
- ps2_data[0] = 0x08 |
- ((p->dx < 0) << 4) | ((p->dy < 0) << 5) | (p->buttons & 0x07);
- ps2_data[1] = mousedev_limit_delta(p->dx, 127);
- ps2_data[2] = mousedev_limit_delta(p->dy, 127);
- p->dx -= ps2_data[1];
- p->dy -= ps2_data[2];
+ ps2_data[0] = BIT(3);
+ ps2_data[0] |= ((dx & BIT(7)) >> 3) | ((dy & BIT(7)) >> 2);
+ ps2_data[0] |= p->buttons & 0x07;
switch (client->mode) {
case MOUSEDEV_EMUL_EXPS:
- ps2_data[3] = mousedev_limit_delta(p->dz, 7);
- p->dz -= ps2_data[3];
- ps2_data[3] = (ps2_data[3] & 0x0f) | ((p->buttons & 0x18) << 1);
+ dz = clamp_val(p->dz, -7, 7);
+ p->dz -= dz;
+
+ ps2_data[3] = (dz & 0x0f) | ((p->buttons & 0x18) << 1);
client->bufsiz = 4;
break;
case MOUSEDEV_EMUL_IMPS:
- ps2_data[0] |=
- ((p->buttons & 0x10) >> 3) | ((p->buttons & 0x08) >> 1);
- ps2_data[3] = mousedev_limit_delta(p->dz, 127);
- p->dz -= ps2_data[3];
+ dz = clamp_val(p->dz, -127, 127);
+ p->dz -= dz;
+
+ ps2_data[0] |= ((p->buttons & 0x10) >> 3) |
+ ((p->buttons & 0x08) >> 1);
+ ps2_data[3] = dz;
+
client->bufsiz = 4;
break;
case MOUSEDEV_EMUL_PS2:
default:
- ps2_data[0] |=
- ((p->buttons & 0x10) >> 3) | ((p->buttons & 0x08) >> 1);
p->dz = 0;
+
+ ps2_data[0] |= ((p->buttons & 0x10) >> 3) |
+ ((p->buttons & 0x08) >> 1);
+
client->bufsiz = 3;
break;
}
@@ -714,7 +718,7 @@ static ssize_t mousedev_read(struct file *file, char __user *buffer,
{
struct mousedev_client *client = file->private_data;
struct mousedev *mousedev = client->mousedev;
- signed char data[sizeof(client->ps2)];
+ u8 data[sizeof(client->ps2)];
int retval = 0;
if (!client->ready && !client->buffer && mousedev->exist &&