| Message ID | 1469557333-9497-1-git-send-email-briannorris@chromium.org |
|---|---|
| State | Accepted |
| Headers | show |
On Tue, Jul 26, 2016 at 11:22:13AM -0700, Brian Norris wrote: > 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> Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> > --- > 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 >
On Tue, Jul 26, 2016 at 11:22:13AM -0700, Brian Norris wrote: > 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> Reviewed-by: Guenter Roeck <linux@roeck-us.net> > --- > 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 > -- To unsubscribe from this list: send the line "unsubscribe linux-pwm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Jul 26, 2016 at 11:22:13AM -0700, Brian Norris wrote: > 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(-) Applied, thanks. Thierry
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;
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(-)