[PATCH] scsi: debug: fix type mismatch warning for sg_pcopy_from_buffer

Arnd Bergmann
2015-05-19T21:23:02Z

The recent change to mark the input argument of sg_pcopy_from_buffer
had the unfortunate side-effect to cause a new warning in the
scsi_debug code:

drivers/scsi/scsi_debug.c: In function 'do_device_access':
drivers/scsi/scsi_debug.c:2376:8: warning: assignment from incompatible pointer type [-Wincompatible-pointer-types]
func = sg_pcopy_from_buffer;

This patch attempts to avoid that warning without adding
evil type casts, but unfortunately makes the do_device_access
function a lot uglier in the process.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 5250326459 ("lib/scatterlist: mark input buffer parameters as 'const'")
---

I can't decide if this is actually a good idea, or if we should rather drop
the sg_pcopy_from_buffer() patch. Maybe someone else sees a better solution.

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 1f8e2dc9c616..dd9f0d1574ef 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -2363,17 +2363,13 @@ do_device_access(struct scsi_cmnd *scmd, u64 lba, u32 num, bool do_write)
u64 block, rest = 0;
struct scsi_data_buffer *sdb;
enum dma_data_direction dir;
- size_t (*func)(struct scatterlist *, unsigned int, void *, size_t,
- off_t);

if (do_write) {
sdb = scsi_out(scmd);
dir = DMA_TO_DEVICE;
- func = sg_pcopy_to_buffer;
} else {
sdb = scsi_in(scmd);
dir = DMA_FROM_DEVICE;
- func = sg_pcopy_from_buffer;
}

if (!sdb->length)
@@ -2385,17 +2381,29 @@ do_device_access(struct scsi_cmnd *scmd, u64 lba, u32 num, bool do_write)
if (block + num > sdebug_store_sectors)
rest = block + num - sdebug_store_sectors;

- ret = func(sdb->table.sgl, sdb->table.nents,
- fake_storep + (block * scsi_debug_sector_size),
- (num - rest) * scsi_debug_sector_size, 0);
+ if (do_write)
+ ret = sg_pcopy_to_buffer(sdb->table.sgl, sdb->table.nents,
+ fake_storep + (block * scsi_debug_sector_size),
+ (num - rest) * scsi_debug_sector_size, 0);
+ else
+ ret = sg_pcopy_from_buffer(sdb->table.sgl, sdb->table.nents,
+ fake_storep + (block * scsi_debug_sector_size),
+ (num - rest) * scsi_debug_sector_size, 0);
+
if (ret != (num - rest) * scsi_debug_sector_size)
return ret;

- if (rest) {
- ret += func(sdb->table.sgl, sdb->table.nents,
- fake_storep, rest * scsi_debug_sector_size,
- (num - rest) * scsi_debug_sector_size);
- }
+ if (!rest)
+ return ret;
+
+ if (do_write)
+ ret += sg_pcopy_to_buffer(sdb->table.sgl, sdb->table.nents,
+ fake_storep, rest * scsi_debug_sector_size,
+ (num - rest) * scsi_debug_sector_size);
+ else
+ ret += sg_pcopy_from_buffer(sdb->table.sgl, sdb->table.nents,
+ fake_storep, rest * scsi_debug_sector_size,
+ (num - rest) * scsi_debug_sector_size);

return ret;
}