Re: [PATCH v3] Input: mousedev - fix implicit conversion warning
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Date: 2017-05-26 17:08:36
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On Fri, May 26, 2017 at 08:40:28AM -0700, Nick Desaulniers wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- * 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. -- Dmitry