[PATCH][next] greybus: Use fallthrough pseudo-keyword

[PATCH][next] greybus: Use fallthrough pseudo-keyword

[Gustavo A. R. Silva]

Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1].

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 drivers/greybus/es2.c       | 2 +-
 drivers/greybus/interface.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/greybus/es2.c b/drivers/greybus/es2.c
index 366716f11b1a..1df6ab5d339d 100644
--- a/drivers/greybus/es2.c
+++ b/drivers/greybus/es2.c
@@ -759,7 +759,7 @@ static int check_urb_status(struct urb *urb)
 	case -EOVERFLOW:
 		dev_err(dev, "%s: overflow actual length is %d\n",
 			__func__, urb->actual_length);
-		/* fall through */
+		fallthrough;
 	case -ECONNRESET:
 	case -ENOENT:
 	case -ESHUTDOWN:
diff --git a/drivers/greybus/interface.c b/drivers/greybus/interface.c
index 67dbe6fda9a1..58ea374d8aaa 100644
--- a/drivers/greybus/interface.c
+++ b/drivers/greybus/interface.c
@@ -1233,7 +1233,7 @@ int gb_interface_add(struct gb_interface *intf)
 	case GB_INTERFACE_TYPE_GREYBUS:
 		dev_info(&intf->dev, "GMP VID=0x%08x, PID=0x%08x\n",
 			 intf->vendor_id, intf->product_id);
-		/* fall-through */
+		fallthrough;
 	case GB_INTERFACE_TYPE_UNIPRO:
 		dev_info(&intf->dev, "DDBL1 Manufacturer=0x%08x, Product=0x%08x\n",
 			 intf->ddbl1_manufacturer_id,
-- 
2.27.0

Re: [PATCH][next] greybus: Use fallthrough pseudo-keyword

[Alex Elder]

On 7/27/20 1:32 PM, Gustavo A. R. Silva wrote:
> Replace the existing /* fall through */ comments and its variants with
> the new pseudo-keyword macro fallthrough[1].
> 
> [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Thanks for the patch.  It looks good, but it raises
another question I'd like discussion on.

It seems that Johan likes default (or final) cases in
switch statements without a "break" statement.  Viresh
and Bryan appear to be fond of this too.

It's pedantic, but I don't like that.  Am I wrong?
   --> Johan/Viresh/Bryan would you please comment?

If they aren't convincing (or don't care) I think break
statements should also be added here:
- In gb_interface_read_and_clear_init_status() for the
   default case
- In gb_interface_activate() for the default case.
- In gb_svc_process_deferred_request() for the default
   case

But let's wait to see what Johan (et al) says.  If you
don't want to do that, say so and I'll do it later.

I looked at the code in drivers/staging/greybus/ and saw
no need to add a "fallthrough" anywhere, but:
- In fw_mgmt_backend_fw_version_operation() Viresh
   seems to have skipped the break in the fault statement
- In gb_uart_request_handler() Bryan did this too.

Depending on discussion, these could be fixed in a
separate patch as well.

These cases aren't found by "checkpatch.pl" because it only
looks at case "blocks" that are followed by another case.
So the last case isn't checked.

					-Alex

> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
>   drivers/greybus/es2.c       | 2 +-
>   drivers/greybus/interface.c | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/greybus/es2.c b/drivers/greybus/es2.c
> index 366716f11b1a..1df6ab5d339d 100644
> --- a/drivers/greybus/es2.c
> +++ b/drivers/greybus/es2.c
> @@ -759,7 +759,7 @@ static int check_urb_status(struct urb *urb)
>   	case -EOVERFLOW:
>   		dev_err(dev, "%s: overflow actual length is %d\n",
>   			__func__, urb->actual_length);
> -		/* fall through */
> +		fallthrough;
>   	case -ECONNRESET:
>   	case -ENOENT:
>   	case -ESHUTDOWN:
> diff --git a/drivers/greybus/interface.c b/drivers/greybus/interface.c
> index 67dbe6fda9a1..58ea374d8aaa 100644
> --- a/drivers/greybus/interface.c
> +++ b/drivers/greybus/interface.c
> @@ -1233,7 +1233,7 @@ int gb_interface_add(struct gb_interface *intf)
>   	case GB_INTERFACE_TYPE_GREYBUS:
>   		dev_info(&intf->dev, "GMP VID=0x%08x, PID=0x%08x\n",
>   			 intf->vendor_id, intf->product_id);
> -		/* fall-through */
> +		fallthrough;
>   	case GB_INTERFACE_TYPE_UNIPRO:
>   		dev_info(&intf->dev, "DDBL1 Manufacturer=0x%08x, Product=0x%08x\n",
>   			 intf->ddbl1_manufacturer_id,
> 

Re: [PATCH][next] greybus: Use fallthrough pseudo-keyword

[Joe Perches]

On Tue, 2020-07-28 at 17:37 -0500, Alex Elder wrote:
> On 7/27/20 1:32 PM, Gustavo A. R. Silva wrote:
> > Replace the existing /* fall through */ comments and its variants with
> > the new pseudo-keyword macro fallthrough[1].
> > 
> > [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through
> 
> Thanks for the patch.  It looks good, but it raises
> another question I'd like discussion on.
> 
> It seems that Johan likes default (or final) cases in
> switch statements without a "break" statement.  Viresh
> and Bryan appear to be fond of this too.
> 
> It's pedantic, but I don't like that.  Am I wrong?

No, you are not wrong.

Re: [greybus-dev] [PATCH][next] greybus: Use fallthrough pseudo-keyword

[Viresh Kumar]

On 28-07-20, 17:37, Alex Elder wrote:
> On 7/27/20 1:32 PM, Gustavo A. R. Silva wrote:
> > Replace the existing /* fall through */ comments and its variants with
> > the new pseudo-keyword macro fallthrough[1].
> > 
> > [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through
> 
> Thanks for the patch.  It looks good, but it raises
> another question I'd like discussion on.
> 
> It seems that Johan likes default (or final) cases in
> switch statements without a "break" statement.  Viresh
> and Bryan appear to be fond of this too.
> 
> It's pedantic, but I don't like that.  Am I wrong?
>   --> Johan/Viresh/Bryan would you please comment?

I am not fond of them as they aren't required for the working of the code. It is
a bit like using an empty return statement for a routine with void return type,
though it surely adds some consistency to the switch case.

But if people really feel it must be there, then its fine :)

-- 
viresh

Re: [greybus-dev] [PATCH][next] greybus: Use fallthrough pseudo-keyword

[Alex Elder]

On 7/29/20 5:51 AM, Viresh Kumar wrote:
> On 28-07-20, 17:37, Alex Elder wrote:
>> On 7/27/20 1:32 PM, Gustavo A. R. Silva wrote:
>>> Replace the existing /* fall through */ comments and its variants with
>>> the new pseudo-keyword macro fallthrough[1].
>>>
>>> [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through
>>
>> Thanks for the patch.  It looks good, but it raises
>> another question I'd like discussion on.
>>
>> It seems that Johan likes default (or final) cases in
>> switch statements without a "break" statement.  Viresh
>> and Bryan appear to be fond of this too.
>>
>> It's pedantic, but I don't like that.  Am I wrong?
>>   --> Johan/Viresh/Bryan would you please comment?
> 
> I am not fond of them as they aren't required for the working of the code. It is
> a bit like using an empty return statement for a routine with void return type,
> though it surely adds some consistency to the switch case.

I understand this perspective, and it's exactly why I wanted
to have a conversation about it (rather than just saying it
should be fixed).  As similar example, I don't like unnecessary
parentheses, but sometimes it's a good idea to have them.

Thanks.

					-Alex

> But if people really feel it must be there, then its fine :)
> 

Re: [PATCH][next] greybus: Use fallthrough pseudo-keyword

[Alex Elder]

On 7/28/20 5:37 PM, Alex Elder wrote:
> On 7/27/20 1:32 PM, Gustavo A. R. Silva wrote:
>> Replace the existing /* fall through */ comments and its variants with
>> the new pseudo-keyword macro fallthrough[1].
>>
>> [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through
> 
> Thanks for the patch.  It looks good, but it raises
> another question I'd like discussion on.

It's been a week, and we heard back from Viresh (and Joe) on
this, but no one else.  Viresh left out the break statement on
the last case of the switch statement intentionally, arguing
that it is not needed (much like a return statement at the end
of a void function).  But he doesn't feel strongly enough
insist it should stay that way.  I'm sure the others omitted
the break statement intentionally as well.

Given no strong pushback, I'll ask you (Gustavo) to post a
second patch adding the missing break statements I described
(and look for any others I might have missed).  If you would
prefer not to do that, just say so, and I will send out such
a patch myself.

On your original patch, it looks good to me.  Thank you.

Reviewed-by: Alex Elder <elder@linaro.org>

> It seems that Johan likes default (or final) cases in
> switch statements without a "break" statement.  Viresh
> and Bryan appear to be fond of this too.
> 
> It's pedantic, but I don't like that.  Am I wrong?
>   --> Johan/Viresh/Bryan would you please comment?
> 
> If they aren't convincing (or don't care) I think break
> statements should also be added here:
> - In gb_interface_read_and_clear_init_status() for the
>   default case
> - In gb_interface_activate() for the default case.
> - In gb_svc_process_deferred_request() for the default
>   case
> 
> But let's wait to see what Johan (et al) says.  If you
> don't want to do that, say so and I'll do it later.
> 
> I looked at the code in drivers/staging/greybus/ and saw
> no need to add a "fallthrough" anywhere, but:
> - In fw_mgmt_backend_fw_version_operation() Viresh
>   seems to have skipped the break in the fault statement
> - In gb_uart_request_handler() Bryan did this too.
> 
> Depending on discussion, these could be fixed in a
> separate patch as well.
> 
> These cases aren't found by "checkpatch.pl" because it only
> looks at case "blocks" that are followed by another case.
> So the last case isn't checked.
> 
>                     -Alex
> 
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>> ---
>>   drivers/greybus/es2.c       | 2 +-
>>   drivers/greybus/interface.c | 2 +-
>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/greybus/es2.c b/drivers/greybus/es2.c
>> index 366716f11b1a..1df6ab5d339d 100644
>> --- a/drivers/greybus/es2.c
>> +++ b/drivers/greybus/es2.c
>> @@ -759,7 +759,7 @@ static int check_urb_status(struct urb *urb)
>>       case -EOVERFLOW:
>>           dev_err(dev, "%s: overflow actual length is %d\n",
>>               __func__, urb->actual_length);
>> -        /* fall through */
>> +        fallthrough;
>>       case -ECONNRESET:
>>       case -ENOENT:
>>       case -ESHUTDOWN:
>> diff --git a/drivers/greybus/interface.c b/drivers/greybus/interface.c
>> index 67dbe6fda9a1..58ea374d8aaa 100644
>> --- a/drivers/greybus/interface.c
>> +++ b/drivers/greybus/interface.c
>> @@ -1233,7 +1233,7 @@ int gb_interface_add(struct gb_interface *intf)
>>       case GB_INTERFACE_TYPE_GREYBUS:
>>           dev_info(&intf->dev, "GMP VID=0x%08x, PID=0x%08x\n",
>>                intf->vendor_id, intf->product_id);
>> -        /* fall-through */
>> +        fallthrough;
>>       case GB_INTERFACE_TYPE_UNIPRO:
>>           dev_info(&intf->dev, "DDBL1 Manufacturer=0x%08x, Product=0x%08x\n",
>>                intf->ddbl1_manufacturer_id,
>>
> 

Re: [PATCH][next] greybus: Use fallthrough pseudo-keyword

[Johan Hovold]

On Wed, Aug 05, 2020 at 08:14:47AM -0500, Alex Elder wrote:
> On 7/28/20 5:37 PM, Alex Elder wrote:
> > On 7/27/20 1:32 PM, Gustavo A. R. Silva wrote:
> >> Replace the existing /* fall through */ comments and its variants with
> >> the new pseudo-keyword macro fallthrough[1].
> >>
> >> [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through
> > 
> > Thanks for the patch.  It looks good, but it raises
> > another question I'd like discussion on.

Sorry about the late reply on this.

> It's been a week, and we heard back from Viresh (and Joe) on
> this, but no one else.  Viresh left out the break statement on
> the last case of the switch statement intentionally, arguing
> that it is not needed (much like a return statement at the end
> of a void function).  But he doesn't feel strongly enough
> insist it should stay that way.  I'm sure the others omitted
> the break statement intentionally as well.

I really don't mind break statements in the final case and often do add
them, but I'm a bit reluctant to suggest that this is something that
need "fixing". There are a ton of these all over the kernel, and I think
we have too many opportunities for people to do mechanical clean ups
already.

Especially after Gustavo's work, the only real argument for adding them
is mostly moot as the compiler would catch it if anyone adds a new case
and forgets about the break statement.

> Given no strong pushback, I'll ask you (Gustavo) to post a
> second patch adding the missing break statements I described
> (and look for any others I might have missed).  If you would
> prefer not to do that, just say so, and I will send out such
> a patch myself.

I'd probably just leave it as is, if only to not inspire others to send
copy-cat "fixes".

Johan