Re: [PATCH] firewire: mark expected switch fall-throughs

From: Stefan Richter
Date: Thu Mar 14 2019 - 06:11:31 EST


(added Cc: Mathieu Malaterre, who sent a patch which is a subset of this)

On Feb 11 Gustavo A. R. Silva wrote:
> In preparation to enabling -Wimplicit-fallthrough, mark switch
> cases where we are expecting to fall through.
>
> This patch fixes the following warnings:
>
> drivers/firewire/core-device.c: In function âset_broadcast_channelâ:
> drivers/firewire/core-device.c:969:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
> if (data & cpu_to_be32(1 << 31)) {
> ^
> drivers/firewire/core-device.c:974:3: note: here
> case RCODE_ADDRESS_ERROR:
> ^~~~
> drivers/firewire/core-iso.c: In function âmanage_channelâ:
> drivers/firewire/core-iso.c:308:7: warning: this statement may fall through [-Wimplicit-fallthrough=]
> if ((data[0] & bit) == (data[1] & bit))
> ^
> drivers/firewire/core-iso.c:312:3: note: here
> default:
> ^~~~~~~
> drivers/firewire/core-topology.c: In function âcount_portsâ:
> drivers/firewire/core-topology.c:69:23: warning: this statement may fall through [-Wimplicit-fallthrough=]
> (*child_port_count)++;
> ~~~~~~~~~~~~~~~~~~~^~
> drivers/firewire/core-topology.c:70:3: note: here
> case SELFID_PORT_PARENT:
> ^~~~
>
> Warning level 3 was used: -Wimplicit-fallthrough=3
>
> Notice that in some cases, the code comment is modified in
> accordance with what GCC is expecting to find.

OK, I looked up
https://gcc.gnu.org/onlinedocs/gcc-8.3.0/gcc/Warning-Options.html#index-Wimplicit-fallthrough
now. I am loudly sighing and rolling my eyes... Anyway; the last regex
listed at the Wimplicit-fallthrough=3 bullet point is obviously the one
you are wanting to match.

> This patch is part of the ongoing efforts to enable
> -Wimplicit-fallthrough.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
> ---
> drivers/firewire/core-device.c | 2 +-
> drivers/firewire/core-iso.c | 2 +-
> drivers/firewire/core-topology.c | 1 +
> 3 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c
> index 7c2eed76011e..0c86548fa4a7 100644
> --- a/drivers/firewire/core-device.c
> +++ b/drivers/firewire/core-device.c
> @@ -970,7 +970,7 @@ static void set_broadcast_channel(struct fw_device *device, int generation)
> device->bc_implemented = BC_IMPLEMENTED;
> break;
> }
> - /* else fall through to case address error */
> + /* else, fall through - to case address error */
> case RCODE_ADDRESS_ERROR:
> device->bc_implemented = BC_UNIMPLEMENTED;
> }
> diff --git a/drivers/firewire/core-iso.c b/drivers/firewire/core-iso.c
> index 35e784cffc23..7e5c98840b80 100644
> --- a/drivers/firewire/core-iso.c
> +++ b/drivers/firewire/core-iso.c
> @@ -308,7 +308,7 @@ static int manage_channel(struct fw_card *card, int irm_id, int generation,
> if ((data[0] & bit) == (data[1] & bit))
> continue;
>
> - /* 1394-1995 IRM, fall through to retry. */
> + /* fall through - to retry for 1394-1995 IRM */

If you don't mind, I will apply your patch with a different wording of this
comment:

/* fall through - It's an 1394-1995 IRM, retry. */

I'll mark my modification to your patch in the signed-off-by-tag.

> default:
> if (retry) {
> retry--;
> diff --git a/drivers/firewire/core-topology.c b/drivers/firewire/core-topology.c
> index 7db234d3fbdd..82c67e900aad 100644
> --- a/drivers/firewire/core-topology.c
> +++ b/drivers/firewire/core-topology.c
> @@ -67,6 +67,7 @@ static u32 *count_ports(u32 *sid, int *total_port_count, int *child_port_count)
> switch (port_type) {
> case SELFID_PORT_CHILD:
> (*child_port_count)++;
> + /* fall through */
> case SELFID_PORT_PARENT:
> case SELFID_PORT_NCONN:
> (*total_port_count)++;

--
Stefan Richter
-======---== --== -===-
http://arcgraph.de/sr/