Messages in this thread Patch in this message | | | From | Brian Norris <> | Subject | [PATCH] pwm: cros_ec: add __packed to prevent padding | Date | Tue, 26 Jul 2016 11:22:13 -0700 |
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While the particular usage in question is likely safe (struct cros_ec_command is 32-bit aligned, followed by <=32-bit fields), it's been suggested this is not a great pattern to follow for the general case -- for example, if we follow a 'struct cros_ec_command' (which is 32-bit- but not 64-bit-aligned) with a struct that starts with a 64-bit type (e.g., u64), the compiler may add padding.
Let's add __packed, to inform the compiler of our true intention -- to have no padding between these struct elements -- and to future proof for any refactorings that might occur.
Signed-off-by: Brian Norris <briannorris@chromium.org> --- Hi Thierry,
I don't know of any bugs directly resolved by this patch, so take it for v4.8/v4.9 at your discretion.
drivers/pwm/pwm-cros-ec.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/pwm/pwm-cros-ec.c b/drivers/pwm/pwm-cros-ec.c index 99b9acc1a420..f6ca4e8c6253 100644 --- a/drivers/pwm/pwm-cros-ec.c +++ b/drivers/pwm/pwm-cros-ec.c @@ -38,7 +38,7 @@ static int cros_ec_pwm_set_duty(struct cros_ec_device *ec, u8 index, u16 duty) struct { struct cros_ec_command msg; struct ec_params_pwm_set_duty params; - } buf; + } __packed buf; struct ec_params_pwm_set_duty *params = &buf.params; struct cros_ec_command *msg = &buf.msg; @@ -65,7 +65,7 @@ static int __cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index, struct ec_params_pwm_get_duty params; struct ec_response_pwm_get_duty resp; }; - } buf; + } __packed buf; struct ec_params_pwm_get_duty *params = &buf.params; struct ec_response_pwm_get_duty *resp = &buf.resp; struct cros_ec_command *msg = &buf.msg; -- 2.8.0.rc3.226.g39d4020
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