Re: [PATCH v4 1/4] can: dev: Add support for limiting configured bitrate

2017-08-17 Thread Sergei Shtylyov 

Hello!

On 08/17/2017 08:54 PM, Franklin S Cooper Jr wrote:


Various CAN or CAN-FD IP may be able to run at a faster rate than
what the transceiver the CAN node is connected to. This can lead to
unexpected errors. However, CAN transceivers typically have fixed
limitations and provide no means to discover these limitations at
runtime. Therefore, add support for a can-transceiver node that
can be reused by other CAN peripheral drivers to determine for both
CAN and CAN-FD what the max bitrate that can be used. If the user
tries to configure CAN to pass these maximum bitrates it will throw
an error.

Signed-off-by: Franklin S Cooper Jr 
---
Version 4 changes:
Used can-transceiver instead of fixed-transceiver.

   drivers/net/can/dev.c   | 50
+
   include/linux/can/dev.h |  5 +
   2 files changed, 55 insertions(+)

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 365a8cc..372108f 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c

[...]

@@ -814,6 +815,39 @@ int open_candev(struct net_device *dev)
   }
   EXPORT_SYMBOL_GPL(open_candev);
   +#ifdef CONFIG_OF
+/*
+ * Common function that can be used to understand the limitation of
+ * a transceiver when it provides no means to determine these
limitations
+ * at runtime.
+ */
+void of_can_transceiver(struct net_device *dev)
+{
+struct device_node *dn;
+struct can_priv *priv = netdev_priv(dev);
+struct device_node *np;
+unsigned int max_bitrate;
+int ret;
+
+np = dev->dev.parent->of_node;


I'd do that as an initializer.


Ok



+
+dn = of_get_child_by_name(np, "can-transceiver");
+if (!dn)
+return;
+
+max_bitrate = 0;
+ret = of_property_read_u32(dn, "max-bitrate", _bitrate);


I'd initialize max_bitrate to 0 as iff of_property_read_u32() fails,
it'll leave the variable unset...>

+
+if (max_bitrate > 0) {


You risk checking unset variable here.


Four lines up I am already setting max_bitrate to a default value of 0.


   Oops, sorry. Don't know how I missed that. Better done as initializer too 
though...


MBR, Sergei

Re: [PATCH v4 1/4] can: dev: Add support for limiting configured bitrate

2017-08-17 Thread Franklin S Cooper Jr 

Hi,
On 08/10/2017 10:29 AM, Marc Kleine-Budde wrote:
> Hello,
> 
> sorry for stepping in late
> 
> On 08/10/2017 02:59 AM, Franklin S Cooper Jr wrote:
>> Various CAN or CAN-FD IP may be able to run at a faster rate than
>> what the transceiver the CAN node is connected to. This can lead to
>> unexpected errors. However, CAN transceivers typically have fixed
>> limitations and provide no means to discover these limitations at
>> runtime. Therefore, add support for a can-transceiver node that
>> can be reused by other CAN peripheral drivers to determine for both
>> CAN and CAN-FD what the max bitrate that can be used. If the user
>> tries to configure CAN to pass these maximum bitrates it will throw
>> an error.
>>
>> Signed-off-by: Franklin S Cooper Jr 
>> ---
>> Version 4 changes:
>> Used can-transceiver instead of fixed-transceiver.
>>
>>  drivers/net/can/dev.c   | 50 
>> +
>>  include/linux/can/dev.h |  5 +
>>  2 files changed, 55 insertions(+)
>>
>> diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
>> index 365a8cc..372108f 100644
>> --- a/drivers/net/can/dev.c
>> +++ b/drivers/net/can/dev.c
>> @@ -27,6 +27,7 @@
>>  #include 
>>  #include 
>>  #include 
>> +#include 
>>  #include 
>>  
>>  #define MOD_DESC "CAN device driver interface"
>> @@ -814,6 +815,39 @@ int open_candev(struct net_device *dev)
>>  }
>>  EXPORT_SYMBOL_GPL(open_candev);
>>  
>> +#ifdef CONFIG_OF
>> +/*
>> + * Common function that can be used to understand the limitation of
>> + * a transceiver when it provides no means to determine these limitations
>> + * at runtime.
>> + */
>> +void of_can_transceiver(struct net_device *dev)
>> +{
>> +struct device_node *dn;
>> +struct can_priv *priv = netdev_priv(dev);
>> +struct device_node *np;
>> +unsigned int max_bitrate;
>> +int ret;
>> +
>> +np = dev->dev.parent->of_node;
>> +
>> +dn = of_get_child_by_name(np, "can-transceiver");
>> +if (!dn)
>> +return;
>> +
>> +max_bitrate = 0;
>> +ret = of_property_read_u32(dn, "max-bitrate", _bitrate);
> 
> IIRC the last argument is only modified in case of no error, so what about:
>   ret = of_property_read_u32(dn, "max-bitrate",
>   >max_bitrate);

That works
> 
>> +
>> +if (max_bitrate > 0) {
>> +priv->max_bitrate = max_bitrate;
>> +priv->is_bitrate_limited = true;
> 
> Do we need is_bitrate_limited...

No.
> 
>> +} else if (ret != -EINVAL) {
>> +netdev_warn(dev, "Invalid value for transceiver max bitrate\n");
>> +}
>> +}
>> +EXPORT_SYMBOL(of_can_transceiver);
>> +#endif
>> +
>>  /*
>>   * Common close function for cleanup before the device gets closed.
>>   *
>> @@ -913,6 +947,14 @@ static int can_changelink(struct net_device *dev, 
>> struct nlattr *tb[],
>>  priv->bitrate_const_cnt);
>>  if (err)
>>  return err;
>> +
>> +if (priv->is_bitrate_limited &&
>> +bt.bitrate > priv->max_bitrate) {
> 
> ...can we just use priv->max_bitrate?

Yes

Thanks for reviewing and for your feedback.
> 
>   if (priv->max_bitrate && bt.bitrate > priv->max_bitrate)
> 
>> +netdev_err(dev, "arbitration bitrate surpasses 
>> transceiver capabilities of %d bps\n",
>> +   priv->max_bitrate);
>> +return -EINVAL;
>> +}
>> +
>>  memcpy(>bittiming, , sizeof(bt));
>>  
>>  if (priv->do_set_bittiming) {
>> @@ -997,6 +1039,14 @@ static int can_changelink(struct net_device *dev, 
>> struct nlattr *tb[],
>>  priv->data_bitrate_const_cnt);
>>  if (err)
>>  return err;
>> +
>> +if (priv->is_bitrate_limited &&
>> +dbt.bitrate > priv->max_bitrate) {
>> +netdev_err(dev, "canfd data bitrate surpasses 
>> transceiver capabilities of %d bps\n",
>> +   priv->max_bitrate);
>> +return -EINVAL;
>> +}
>> +
>>  memcpy(>data_bittiming, , sizeof(dbt));
>>  
>>  if (priv->do_set_data_bittiming) {
>> diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
>> index 141b05a..5519f59 100644
>> --- a/include/linux/can/dev.h
>> +++ b/include/linux/can/dev.h
>> @@ -47,6 +47,9 @@ struct can_priv {
>>  unsigned int data_bitrate_const_cnt;
>>  struct can_clock clock;
>>  
>> +unsigned int max_bitrate;
>> +bool is_bitrate_limited;
>> +
>>  enum can_state state;
>>  
>>  /* CAN controller features - see include/uapi/linux/can/netlink.h */
>> @@ -165,6 +168,8 @@ void can_put_echo_skb(struct sk_buff *skb, struct 
>> net_device *dev,
>>  unsigned int can_get_echo_skb(struct net_device *dev, unsigned int idx);
>>  void can_free_echo_skb(struct net_device *dev, unsigned int idx);
>>  
>>

Re: [PATCH v4 1/4] can: dev: Add support for limiting configured bitrate

2017-08-17 Thread Franklin S Cooper Jr 


On 08/10/2017 05:05 AM, Sergei Shtylyov wrote:
> Hello!
> 
> On 8/10/2017 3:59 AM, Franklin S Cooper Jr wrote:
> 
>> Various CAN or CAN-FD IP may be able to run at a faster rate than
>> what the transceiver the CAN node is connected to. This can lead to
>> unexpected errors. However, CAN transceivers typically have fixed
>> limitations and provide no means to discover these limitations at
>> runtime. Therefore, add support for a can-transceiver node that
>> can be reused by other CAN peripheral drivers to determine for both
>> CAN and CAN-FD what the max bitrate that can be used. If the user
>> tries to configure CAN to pass these maximum bitrates it will throw
>> an error.
>>
>> Signed-off-by: Franklin S Cooper Jr 
>> ---
>> Version 4 changes:
>> Used can-transceiver instead of fixed-transceiver.
>>
>>   drivers/net/can/dev.c   | 50
>> +
>>   include/linux/can/dev.h |  5 +
>>   2 files changed, 55 insertions(+)
>>
>> diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
>> index 365a8cc..372108f 100644
>> --- a/drivers/net/can/dev.c
>> +++ b/drivers/net/can/dev.c
> [...]
>> @@ -814,6 +815,39 @@ int open_candev(struct net_device *dev)
>>   }
>>   EXPORT_SYMBOL_GPL(open_candev);
>>   +#ifdef CONFIG_OF
>> +/*
>> + * Common function that can be used to understand the limitation of
>> + * a transceiver when it provides no means to determine these
>> limitations
>> + * at runtime.
>> + */
>> +void of_can_transceiver(struct net_device *dev)
>> +{
>> +struct device_node *dn;
>> +struct can_priv *priv = netdev_priv(dev);
>> +struct device_node *np;
>> +unsigned int max_bitrate;
>> +int ret;
>> +
>> +np = dev->dev.parent->of_node;
> 
>I'd do that as an initializer.

Ok
> 
>> +
>> +dn = of_get_child_by_name(np, "can-transceiver");
>> +if (!dn)
>> +return;
>> +
>> +max_bitrate = 0;
>> +ret = of_property_read_u32(dn, "max-bitrate", _bitrate);
> 
>I'd initialize max_bitrate to 0 as iff of_property_read_u32() fails,
> it'll leave the variable unset...>
>> +
>> +if (max_bitrate > 0) {
> 
>You risk checking unset variable here.

Four lines up I am already setting max_bitrate to a default value of 0.

> 
>> +priv->max_bitrate = max_bitrate;
>> +priv->is_bitrate_limited = true;
>> +} else if (ret != -EINVAL) {
>> +netdev_warn(dev, "Invalid value for transceiver max bitrate\n");
>> +}
>> +}
>> +EXPORT_SYMBOL(of_can_transceiver);
>> +#endif
>> +
>>   /*
>>* Common close function for cleanup before the device gets closed.
>>*
> [...]
> 
> MBR, Sergei

Re: [PATCH v4 1/4] can: dev: Add support for limiting configured bitrate

2017-08-10 Thread Marc Kleine-Budde 
Hello,

sorry for stepping in late

On 08/10/2017 02:59 AM, Franklin S Cooper Jr wrote:
> Various CAN or CAN-FD IP may be able to run at a faster rate than
> what the transceiver the CAN node is connected to. This can lead to
> unexpected errors. However, CAN transceivers typically have fixed
> limitations and provide no means to discover these limitations at
> runtime. Therefore, add support for a can-transceiver node that
> can be reused by other CAN peripheral drivers to determine for both
> CAN and CAN-FD what the max bitrate that can be used. If the user
> tries to configure CAN to pass these maximum bitrates it will throw
> an error.
> 
> Signed-off-by: Franklin S Cooper Jr 
> ---
> Version 4 changes:
> Used can-transceiver instead of fixed-transceiver.
> 
>  drivers/net/can/dev.c   | 50 
> +
>  include/linux/can/dev.h |  5 +
>  2 files changed, 55 insertions(+)
> 
> diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
> index 365a8cc..372108f 100644
> --- a/drivers/net/can/dev.c
> +++ b/drivers/net/can/dev.c
> @@ -27,6 +27,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  #include 
>  
>  #define MOD_DESC "CAN device driver interface"
> @@ -814,6 +815,39 @@ int open_candev(struct net_device *dev)
>  }
>  EXPORT_SYMBOL_GPL(open_candev);
>  
> +#ifdef CONFIG_OF
> +/*
> + * Common function that can be used to understand the limitation of
> + * a transceiver when it provides no means to determine these limitations
> + * at runtime.
> + */
> +void of_can_transceiver(struct net_device *dev)
> +{
> + struct device_node *dn;
> + struct can_priv *priv = netdev_priv(dev);
> + struct device_node *np;
> + unsigned int max_bitrate;
> + int ret;
> +
> + np = dev->dev.parent->of_node;
> +
> + dn = of_get_child_by_name(np, "can-transceiver");
> + if (!dn)
> + return;
> +
> + max_bitrate = 0;
> + ret = of_property_read_u32(dn, "max-bitrate", _bitrate);

IIRC the last argument is only modified in case of no error, so what about:
ret = of_property_read_u32(dn, "max-bitrate",
>max_bitrate);

> +
> + if (max_bitrate > 0) {
> + priv->max_bitrate = max_bitrate;
> + priv->is_bitrate_limited = true;

Do we need is_bitrate_limited...

> + } else if (ret != -EINVAL) {
> + netdev_warn(dev, "Invalid value for transceiver max bitrate\n");
> + }
> +}
> +EXPORT_SYMBOL(of_can_transceiver);
> +#endif
> +
>  /*
>   * Common close function for cleanup before the device gets closed.
>   *
> @@ -913,6 +947,14 @@ static int can_changelink(struct net_device *dev, struct 
> nlattr *tb[],
>   priv->bitrate_const_cnt);
>   if (err)
>   return err;
> +
> + if (priv->is_bitrate_limited &&
> + bt.bitrate > priv->max_bitrate) {

...can we just use priv->max_bitrate?

if (priv->max_bitrate && bt.bitrate > priv->max_bitrate)

> + netdev_err(dev, "arbitration bitrate surpasses 
> transceiver capabilities of %d bps\n",
> +priv->max_bitrate);
> + return -EINVAL;
> + }
> +
>   memcpy(>bittiming, , sizeof(bt));
>  
>   if (priv->do_set_bittiming) {
> @@ -997,6 +1039,14 @@ static int can_changelink(struct net_device *dev, 
> struct nlattr *tb[],
>   priv->data_bitrate_const_cnt);
>   if (err)
>   return err;
> +
> + if (priv->is_bitrate_limited &&
> + dbt.bitrate > priv->max_bitrate) {
> + netdev_err(dev, "canfd data bitrate surpasses 
> transceiver capabilities of %d bps\n",
> +priv->max_bitrate);
> + return -EINVAL;
> + }
> +
>   memcpy(>data_bittiming, , sizeof(dbt));
>  
>   if (priv->do_set_data_bittiming) {
> diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
> index 141b05a..5519f59 100644
> --- a/include/linux/can/dev.h
> +++ b/include/linux/can/dev.h
> @@ -47,6 +47,9 @@ struct can_priv {
>   unsigned int data_bitrate_const_cnt;
>   struct can_clock clock;
>  
> + unsigned int max_bitrate;
> + bool is_bitrate_limited;
> +
>   enum can_state state;
>  
>   /* CAN controller features - see include/uapi/linux/can/netlink.h */
> @@ -165,6 +168,8 @@ void can_put_echo_skb(struct sk_buff *skb, struct 
> net_device *dev,
>  unsigned int can_get_echo_skb(struct net_device *dev, unsigned int idx);
>  void can_free_echo_skb(struct net_device *dev, unsigned int idx);
>  
> +void of_can_transceiver(struct net_device *dev);
> +
>  struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf);
>  struct sk_buff *alloc_canfd_skb(struct net_device *dev,
>

Re: [PATCH v4 1/4] can: dev: Add support for limiting configured bitrate

2017-08-10 Thread Sergei Shtylyov 

Hello!

On 8/10/2017 3:59 AM, Franklin S Cooper Jr wrote:


Various CAN or CAN-FD IP may be able to run at a faster rate than
what the transceiver the CAN node is connected to. This can lead to
unexpected errors. However, CAN transceivers typically have fixed
limitations and provide no means to discover these limitations at
runtime. Therefore, add support for a can-transceiver node that
can be reused by other CAN peripheral drivers to determine for both
CAN and CAN-FD what the max bitrate that can be used. If the user
tries to configure CAN to pass these maximum bitrates it will throw
an error.

Signed-off-by: Franklin S Cooper Jr 
---
Version 4 changes:
Used can-transceiver instead of fixed-transceiver.

  drivers/net/can/dev.c   | 50 +
  include/linux/can/dev.h |  5 +
  2 files changed, 55 insertions(+)

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 365a8cc..372108f 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c

[...]

@@ -814,6 +815,39 @@ int open_candev(struct net_device *dev)
  }
  EXPORT_SYMBOL_GPL(open_candev);
  
+#ifdef CONFIG_OF

+/*
+ * Common function that can be used to understand the limitation of
+ * a transceiver when it provides no means to determine these limitations
+ * at runtime.
+ */
+void of_can_transceiver(struct net_device *dev)
+{
+   struct device_node *dn;
+   struct can_priv *priv = netdev_priv(dev);
+   struct device_node *np;
+   unsigned int max_bitrate;
+   int ret;
+
+   np = dev->dev.parent->of_node;


   I'd do that as an initializer.


+
+   dn = of_get_child_by_name(np, "can-transceiver");
+   if (!dn)
+   return;
+
+   max_bitrate = 0;
+   ret = of_property_read_u32(dn, "max-bitrate", _bitrate);


   I'd initialize max_bitrate to 0 as iff of_property_read_u32() fails, it'll 
leave the variable unset...



+
+   if (max_bitrate > 0) {


   You risk checking unset variable here.


+   priv->max_bitrate = max_bitrate;
+   priv->is_bitrate_limited = true;
+   } else if (ret != -EINVAL) {
+   netdev_warn(dev, "Invalid value for transceiver max bitrate\n");
+   }
+}
+EXPORT_SYMBOL(of_can_transceiver);
+#endif
+
  /*
   * Common close function for cleanup before the device gets closed.
   *

[...]

MBR, Sergei

[PATCH v4 1/4] can: dev: Add support for limiting configured bitrate

2017-08-09 Thread Franklin S Cooper Jr 
Various CAN or CAN-FD IP may be able to run at a faster rate than
what the transceiver the CAN node is connected to. This can lead to
unexpected errors. However, CAN transceivers typically have fixed
limitations and provide no means to discover these limitations at
runtime. Therefore, add support for a can-transceiver node that
can be reused by other CAN peripheral drivers to determine for both
CAN and CAN-FD what the max bitrate that can be used. If the user
tries to configure CAN to pass these maximum bitrates it will throw
an error.

Signed-off-by: Franklin S Cooper Jr 
---
Version 4 changes:
Used can-transceiver instead of fixed-transceiver.

 drivers/net/can/dev.c   | 50 +
 include/linux/can/dev.h |  5 +
 2 files changed, 55 insertions(+)

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 365a8cc..372108f 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -27,6 +27,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 
 #define MOD_DESC "CAN device driver interface"
@@ -814,6 +815,39 @@ int open_candev(struct net_device *dev)
 }
 EXPORT_SYMBOL_GPL(open_candev);
 
+#ifdef CONFIG_OF
+/*
+ * Common function that can be used to understand the limitation of
+ * a transceiver when it provides no means to determine these limitations
+ * at runtime.
+ */
+void of_can_transceiver(struct net_device *dev)
+{
+   struct device_node *dn;
+   struct can_priv *priv = netdev_priv(dev);
+   struct device_node *np;
+   unsigned int max_bitrate;
+   int ret;
+
+   np = dev->dev.parent->of_node;
+
+   dn = of_get_child_by_name(np, "can-transceiver");
+   if (!dn)
+   return;
+
+   max_bitrate = 0;
+   ret = of_property_read_u32(dn, "max-bitrate", _bitrate);
+
+   if (max_bitrate > 0) {
+   priv->max_bitrate = max_bitrate;
+   priv->is_bitrate_limited = true;
+   } else if (ret != -EINVAL) {
+   netdev_warn(dev, "Invalid value for transceiver max bitrate\n");
+   }
+}
+EXPORT_SYMBOL(of_can_transceiver);
+#endif
+
 /*
  * Common close function for cleanup before the device gets closed.
  *
@@ -913,6 +947,14 @@ static int can_changelink(struct net_device *dev, struct 
nlattr *tb[],
priv->bitrate_const_cnt);
if (err)
return err;
+
+   if (priv->is_bitrate_limited &&
+   bt.bitrate > priv->max_bitrate) {
+   netdev_err(dev, "arbitration bitrate surpasses 
transceiver capabilities of %d bps\n",
+  priv->max_bitrate);
+   return -EINVAL;
+   }
+
memcpy(>bittiming, , sizeof(bt));
 
if (priv->do_set_bittiming) {
@@ -997,6 +1039,14 @@ static int can_changelink(struct net_device *dev, struct 
nlattr *tb[],
priv->data_bitrate_const_cnt);
if (err)
return err;
+
+   if (priv->is_bitrate_limited &&
+   dbt.bitrate > priv->max_bitrate) {
+   netdev_err(dev, "canfd data bitrate surpasses 
transceiver capabilities of %d bps\n",
+  priv->max_bitrate);
+   return -EINVAL;
+   }
+
memcpy(>data_bittiming, , sizeof(dbt));
 
if (priv->do_set_data_bittiming) {
diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
index 141b05a..5519f59 100644
--- a/include/linux/can/dev.h
+++ b/include/linux/can/dev.h
@@ -47,6 +47,9 @@ struct can_priv {
unsigned int data_bitrate_const_cnt;
struct can_clock clock;
 
+   unsigned int max_bitrate;
+   bool is_bitrate_limited;
+
enum can_state state;
 
/* CAN controller features - see include/uapi/linux/can/netlink.h */
@@ -165,6 +168,8 @@ void can_put_echo_skb(struct sk_buff *skb, struct 
net_device *dev,
 unsigned int can_get_echo_skb(struct net_device *dev, unsigned int idx);
 void can_free_echo_skb(struct net_device *dev, unsigned int idx);
 
+void of_can_transceiver(struct net_device *dev);
+
 struct sk_buff *alloc_can_skb(struct net_device *dev, struct can_frame **cf);
 struct sk_buff *alloc_canfd_skb(struct net_device *dev,
struct canfd_frame **cfd);
-- 
2.9.4.dirty