Re: [PATCH] pwm: cros_ec: add __packed to prevent padding

[Thierry Reding]

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 
> ---
> 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


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Re: [PATCH] pwm: cros_ec: add __packed to prevent padding

[Thierry Reding]

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 
> ---
> 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


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Re: [PATCH] pwm: cros_ec: add __packed to prevent padding

[Thierry Reding]

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 
> ---
> 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


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Re: [PATCH] pwm: cros_ec: add __packed to prevent padding

[Thierry Reding]

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 
> ---
> 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


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Re: [PATCH] pwm: cros_ec: add __packed to prevent padding

[Guenter Roeck]

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 

Reviewed-by: Guenter Roeck 

> ---
> 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 = 
>   struct cros_ec_command *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 = 
>   struct ec_response_pwm_get_duty *resp = 
>   struct cros_ec_command *msg = 
> -- 
> 2.8.0.rc3.226.g39d4020
> 

Re: [PATCH] pwm: cros_ec: add __packed to prevent padding

[Guenter Roeck]

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 

Reviewed-by: Guenter Roeck 

> ---
> 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 = 
>   struct cros_ec_command *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 = 
>   struct ec_response_pwm_get_duty *resp = 
>   struct cros_ec_command *msg = 
> -- 
> 2.8.0.rc3.226.g39d4020
> 

Re: [PATCH] pwm: cros_ec: add __packed to prevent padding

[Dmitry Torokhov]

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 

Reviewed-by: Dmitry Torokhov 

> ---
> 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 = 
>   struct cros_ec_command *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 = 
>   struct ec_response_pwm_get_duty *resp = 
>   struct cros_ec_command *msg = 
> -- 
> 2.8.0.rc3.226.g39d4020
> 

-- 
Dmitry

Re: [PATCH] pwm: cros_ec: add __packed to prevent padding

[Dmitry Torokhov]

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 

Reviewed-by: Dmitry Torokhov 

> ---
> 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 = 
>   struct cros_ec_command *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 = 
>   struct ec_response_pwm_get_duty *resp = 
>   struct cros_ec_command *msg = 
> -- 
> 2.8.0.rc3.226.g39d4020
> 

-- 
Dmitry