USB: serial: io_edgeport: mark expected switch fall-throughs

USB: serial: io_edgeport: mark expected switch fall-throughs

[Gustavo A. R. Silva]

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/usb/serial/io_edgeport.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
index 97c69d3..441dab6 100644
--- a/drivers/usb/serial/io_edgeport.c
+++ b/drivers/usb/serial/io_edgeport.c
@@ -1760,7 +1760,7 @@ static void process_rcvd_data(struct edgeport_serial *edge_serial,
 				edge_serial->rxState = EXPECT_HDR2;
 				break;
 			}
-			/* otherwise, drop on through */
+			/* else: fall through */
 		case EXPECT_HDR2:
 			edge_serial->rxHeader2 = *buffer;
 			++buffer;
@@ -1820,7 +1820,7 @@ static void process_rcvd_data(struct edgeport_serial *edge_serial,
 					edge_serial->rxState = EXPECT_DATA;
 					break;
 				}
-				/* Else, drop through */
+				/* else: fall through */
 			}
 		case EXPECT_DATA: /* Expect data */
 			if (bufferLength < edge_serial->rxBytesRemaining) {

USB: serial: io_edgeport: mark expected switch fall-throughs

[Johan Hovold]

On Thu, Jun 28, 2018 at 01:40:30PM -0500, Gustavo A. R. Silva wrote:
> In preparation to enabling -Wimplicit-fallthrough, mark switch cases
> where we are expecting to fall through.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  drivers/usb/serial/io_edgeport.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
> index 97c69d3..441dab6 100644
> --- a/drivers/usb/serial/io_edgeport.c
> +++ b/drivers/usb/serial/io_edgeport.c
> @@ -1760,7 +1760,7 @@ static void process_rcvd_data(struct edgeport_serial *edge_serial,
>  				edge_serial->rxState = EXPECT_HDR2;
>  				break;
>  			}
> -			/* otherwise, drop on through */
> +			/* else: fall through */

This doesn't silence the compiler warning with gcc 7.2.0 as the "else: "
pattern isn't recognised.

>  		case EXPECT_HDR2:
>  			edge_serial->rxHeader2 = *buffer;
>  			++buffer;
> @@ -1820,7 +1820,7 @@ static void process_rcvd_data(struct edgeport_serial *edge_serial,
>  					edge_serial->rxState = EXPECT_DATA;
>  					break;
>  				}
> -				/* Else, drop through */
> +				/* else: fall through */
>  			}

And this doesn't work either due to the "else: " as well as the fact
that the compiler expects the fallthrough comment to precede the case
statement directly (e.g. it would need to be moved out of the else
block, but that isn't necessarily desirable as we discussed last year: 

	lkml.kernel.org/r/20171027203906.GA7054@embeddedor.com

)

>  		case EXPECT_DATA: /* Expect data */
>  			if (bufferLength < edge_serial->rxBytesRemaining) {

How do you compile test these these patches?

Thanks,
Johan
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USB: serial: io_edgeport: mark expected switch fall-throughs

[Gustavo A. R. Silva]

Hi Johan,

On 07/02/2018 03:51 AM, Johan Hovold wrote:
> On Thu, Jun 28, 2018 at 01:40:30PM -0500, Gustavo A. R. Silva wrote:
>> In preparation to enabling -Wimplicit-fallthrough, mark switch cases
>> where we are expecting to fall through.
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
>> ---
>>  drivers/usb/serial/io_edgeport.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
>> index 97c69d3..441dab6 100644
>> --- a/drivers/usb/serial/io_edgeport.c
>> +++ b/drivers/usb/serial/io_edgeport.c
>> @@ -1760,7 +1760,7 @@ static void process_rcvd_data(struct edgeport_serial *edge_serial,
>>  				edge_serial->rxState = EXPECT_HDR2;
>>  				break;
>>  			}
>> -			/* otherwise, drop on through */
>> +			/* else: fall through */
> 
> This doesn't silence the compiler warning with gcc 7.2.0 as the "else: "
> pattern isn't recognised.
> 

I'm using level 2:

-Wimplicit-fallthrough=2

The thing here is that some people have pointed out that it can be misleading to
place a plain fall-through comment after an if-else code block containing a "break".
So, the solution above has proved to be a good one.

>>  		case EXPECT_HDR2:
>>  			edge_serial->rxHeader2 = *buffer;
>>  			++buffer;
>> @@ -1820,7 +1820,7 @@ static void process_rcvd_data(struct edgeport_serial *edge_serial,
>>  					edge_serial->rxState = EXPECT_DATA;
>>  					break;
>>  				}
>> -				/* Else, drop through */
>> +				/* else: fall through */
>>  			}
> 
> And this doesn't work either due to the "else: " as well as the fact
> that the compiler expects the fallthrough comment to precede the case
> statement directly (e.g. it would need to be moved out of the else
> block, but that isn't necessarily desirable as we discussed last year: 
> 
> 	lkml.kernel.org/r/20171027203906.GA7054@embeddedor.com
> 

Yes. I'm aware of that. This certainly is still triggering a warning, so I just consider this
as a temporal approach. I still need to define how are we going to manage cases like this.

> )
> 
>>  		case EXPECT_DATA: /* Expect data */
>>  			if (bufferLength < edge_serial->rxBytesRemaining) {
> 
> How do you compile test these these patches?
>

I already explained this above.

Thanks for your comments.
---
Gustavo
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USB: serial: io_edgeport: mark expected switch fall-throughs

[Johan Hovold]

On Mon, Jul 02, 2018 at 08:00:43AM -0500, Gustavo A. R. Silva wrote:
> Hi Johan,
> 
> On 07/02/2018 03:51 AM, Johan Hovold wrote:
> > On Thu, Jun 28, 2018 at 01:40:30PM -0500, Gustavo A. R. Silva wrote:
> >> In preparation to enabling -Wimplicit-fallthrough, mark switch cases
> >> where we are expecting to fall through.
> >>
> >> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> >> ---
> >>  drivers/usb/serial/io_edgeport.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/usb/serial/io_edgeport.c b/drivers/usb/serial/io_edgeport.c
> >> index 97c69d3..441dab6 100644
> >> --- a/drivers/usb/serial/io_edgeport.c
> >> +++ b/drivers/usb/serial/io_edgeport.c
> >> @@ -1760,7 +1760,7 @@ static void process_rcvd_data(struct edgeport_serial *edge_serial,
> >>  				edge_serial->rxState = EXPECT_HDR2;
> >>  				break;
> >>  			}
> >> -			/* otherwise, drop on through */
> >> +			/* else: fall through */
> > 
> > This doesn't silence the compiler warning with gcc 7.2.0 as the "else: "
> > pattern isn't recognised.
> > 
> 
> I'm using level 2:
> 
> -Wimplicit-fallthrough=2
> 
> The thing here is that some people have pointed out that it can be misleading to
> place a plain fall-through comment after an if-else code block containing a "break".
> So, the solution above has proved to be a good one.

I don't mind the "else", but I would expect you to mention in the commit
message that you're now relying on the non-default warning level (2).

> >>  		case EXPECT_HDR2:
> >>  			edge_serial->rxHeader2 = *buffer;
> >>  			++buffer;
> >> @@ -1820,7 +1820,7 @@ static void process_rcvd_data(struct edgeport_serial *edge_serial,
> >>  					edge_serial->rxState = EXPECT_DATA;
> >>  					break;
> >>  				}
> >> -				/* Else, drop through */
> >> +				/* else: fall through */
> >>  			}
> > 
> > And this doesn't work either due to the "else: " as well as the fact
> > that the compiler expects the fallthrough comment to precede the case
> > statement directly (e.g. it would need to be moved out of the else
> > block, but that isn't necessarily desirable as we discussed last year: 
> > 
> > 	lkml.kernel.org/r/20171027203906.GA7054@embeddedor.com
> > 
> 
> Yes. I'm aware of that. This certainly is still triggering a warning,
> so I just consider this
> as a temporal approach. I still need to define how are we going to
> manage cases like this.

Ok, so why did you not mention that in the commit message?

If this isn't even addressing the warning you get with the non-default
-Wimplicit-fallthrough=2, I don't see this as much of an improvement.

Might as well leave this unchanged, until all warnings in that switch
statement are addressed.

Johan
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