[PATCH] firewire: fix function type cast warning

From: Arnd Bergmann
Date: Mon Oct 26 2020 - 17:51:45 EST


From: Arnd Bergmann <arnd@xxxxxxxx>

gcc -Wextra complains about a suspicious cast:

rivers/firewire/core-cdev.c:985:8: warning: cast between incompatible function types from ‘void (*)(struct fw_iso_context *, dma_addr_t, void *)’ {aka ‘void (*)(struct fw_iso_context *, long long unsigned int, void *)’} to ‘void (*)(struct fw_iso_context *, u32, size_t, void *, void *)’ {aka ‘void (*)(struct fw_iso_context *, unsigned int, long unsigned int, void *, void *)’} [-Wcast-function-type]

The behavior is correct in the end, but this is more clearly
expressed using a transparent union.

Fixes: 872e330e3880 ("firewire: add isochronous multichannel reception")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
drivers/firewire/core-cdev.c | 6 +++---
drivers/firewire/core-iso.c | 2 +-
include/linux/firewire.h | 17 ++++++++---------
3 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index fb6c651214f3..8d85d52b02ca 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -970,7 +970,7 @@ static int ioctl_create_iso_context(struct client *client, union ioctl_arg *arg)
if (a->speed > SCODE_3200 || a->channel > 63)
return -EINVAL;

- cb = iso_callback;
+ cb.sc = iso_callback;
break;

case FW_ISO_CONTEXT_RECEIVE:
@@ -978,11 +978,11 @@ static int ioctl_create_iso_context(struct client *client, union ioctl_arg *arg)
a->channel > 63)
return -EINVAL;

- cb = iso_callback;
+ cb.sc = iso_callback;
break;

case FW_ISO_CONTEXT_RECEIVE_MULTICHANNEL:
- cb = (fw_iso_callback_t)iso_mc_callback;
+ cb.mc = iso_mc_callback;
break;

default:
diff --git a/drivers/firewire/core-iso.c b/drivers/firewire/core-iso.c
index af70e74f9a7e..ddada648775a 100644
--- a/drivers/firewire/core-iso.c
+++ b/drivers/firewire/core-iso.c
@@ -145,7 +145,7 @@ struct fw_iso_context *fw_iso_context_create(struct fw_card *card,
ctx->channel = channel;
ctx->speed = speed;
ctx->header_size = header_size;
- ctx->callback.sc = callback;
+ ctx->callback = callback;
ctx->callback_data = callback_data;

return ctx;
diff --git a/include/linux/firewire.h b/include/linux/firewire.h
index aec8f30ab200..59b5e02a6d42 100644
--- a/include/linux/firewire.h
+++ b/include/linux/firewire.h
@@ -431,11 +431,13 @@ void fw_iso_buffer_destroy(struct fw_iso_buffer *buffer, struct fw_card *card);
size_t fw_iso_buffer_lookup(struct fw_iso_buffer *buffer, dma_addr_t completed);

struct fw_iso_context;
-typedef void (*fw_iso_callback_t)(struct fw_iso_context *context,
- u32 cycle, size_t header_length,
- void *header, void *data);
-typedef void (*fw_iso_mc_callback_t)(struct fw_iso_context *context,
- dma_addr_t completed, void *data);
+typedef union {
+ void (*sc)(struct fw_iso_context *context, u32 cycle,
+ size_t header_length, void *header, void *data);
+ void (*mc)(struct fw_iso_context *context, dma_addr_t completed,
+ void *data);
+} __attribute__ ((__transparent_union__)) fw_iso_callback_t;
+
struct fw_iso_context {
struct fw_card *card;
int type;
@@ -443,10 +445,7 @@ struct fw_iso_context {
int speed;
bool drop_overflow_headers;
size_t header_size;
- union {
- fw_iso_callback_t sc;
- fw_iso_mc_callback_t mc;
- } callback;
+ fw_iso_callback_t callback;
void *callback_data;
};

--
2.27.0