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H A D | ad7314.c | 984faa1f Thu Jan 22 16:44:13 CST 2015 Rasmus Villemoes <linux@rasmusvillemoes.dk> hwmon: (ad7314) Do proper sign extension
The comment above (data << 2) >> 2 explains what the intention is: To use bit 13 of the 14-bit value data as the sign bit. However, this doesn't work due to C's promotion rules. data has type s16, but data << 2 has type int. To get sign extension, that expression would have to be cast back to an s16 before being shifted (at which point C's promotion rules would then kick in again and promote the left operand to int). As it stands, both expressions are no-ops for any value of data.
Avoid these subtleties by using the existing API for this. sign_extend32 works equally well for 8 and 16 bit types.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Guenter Roeck <linux@roeck-us.net> 984faa1f Thu Jan 22 16:44:13 CST 2015 Rasmus Villemoes <linux@rasmusvillemoes.dk> hwmon: (ad7314) Do proper sign extension The comment above (data << 2) >> 2 explains what the intention is: To use bit 13 of the 14-bit value data as the sign bit. However, this doesn't work due to C's promotion rules. data has type s16, but data << 2 has type int. To get sign extension, that expression would have to be cast back to an s16 before being shifted (at which point C's promotion rules would then kick in again and promote the left operand to int). As it stands, both expressions are no-ops for any value of data. Avoid these subtleties by using the existing API for this. sign_extend32 works equally well for 8 and 16 bit types. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
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