| Message ID | 20170526154029.9405-1-nick.desaulniers@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, May 26, 2017 at 08:40:28AM -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. > > Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com> > --- > * Additionally change function signature for the lone function dealing > with ps2 data. > > drivers/input/mousedev.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/input/mousedev.c b/drivers/input/mousedev.c > index 0e0ff84088fd..0e31a109b1b4 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; > @@ -577,7 +577,7 @@ static inline int mousedev_limit_delta(int delta, int limit) > } > > static void mousedev_packet(struct mousedev_client *client, > - signed char *ps2_data) > + unsigned char *ps2_data) > { > struct mousedev_motion *p = &client->packets[client->tail]; If you look at the code of this fucntion we really use ps2_data as signed in calculations, and this change would break that. While making ps2_data u8 might be beneficial we'd need to rework mousedev_packet() to use signed temporaries for dx, dy and dz before stufifng them into ps2_data. Thanks.
On Fri, May 26, 2017 at 10:07:46AM -0700, Dmitry Torokhov wrote: > If you look at the code of this fucntion we really use ps2_data as > signed in calculations, and this change would break that. While making > ps2_data u8 might be beneficial we'd need to rework mousedev_packet() to > use signed temporaries for dx, dy and dz before stufifng them into > ps2_data. Is your recommendation then to stick with the simple cast as in V1 of this patch, or stick with u8 and rework mousedev_packet()? -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, May 29, 2017 at 12:22:52PM -0700, Nick Desaulniers wrote: > On Fri, May 26, 2017 at 10:07:46AM -0700, Dmitry Torokhov wrote: > > If you look at the code of this fucntion we really use ps2_data as > > signed in calculations, and this change would break that. While making > > ps2_data u8 might be beneficial we'd need to rework mousedev_packet() to > > use signed temporaries for dx, dy and dz before stufifng them into > > ps2_data. > > Is your recommendation then to stick with the simple cast as in V1 of > this patch, or stick with u8 and rework mousedev_packet()? I think casts are often mysterious, so, unless we'll end up with worse object code, I'd switch to u8 and temps.
diff --git a/drivers/input/mousedev.c b/drivers/input/mousedev.c index 0e0ff84088fd..0e31a109b1b4 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; @@ -577,7 +577,7 @@ static inline int mousedev_limit_delta(int delta, int limit) } static void mousedev_packet(struct mousedev_client *client, - signed char *ps2_data) + unsigned char *ps2_data) { struct mousedev_motion *p = &client->packets[client->tail];
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. Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com> --- * Additionally change function signature for the lone function dealing with ps2 data. drivers/input/mousedev.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)