Hi Jonathan,
Thanks once again for the review :)
On 23/11/2024 18:37, Jonathan Cameron wrote:
On Thu, 21 Nov 2024 10:20:07 +0200
Matti Vaittinen <mazziesaccount@xxxxxxxxx> wrote:
The error path in the gain_to_scaletables() uses goto for unwinding an
allocation on failure. This can be slightly simplified by using the
automated free when exiting the scope.
Use __free(kfree) and drop the goto based error handling.
Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
---
Revision history:
v1 => v2:
- patch number changed because a change was added to the series.
- rebased on iio/testing to avoid conflicts with queued fixes
---
drivers/iio/industrialio-gts-helper.c | 19 ++++++++-----------
1 file changed, 8 insertions(+), 11 deletions(-)
diff --git a/drivers/iio/industrialio-gts-helper.c b/drivers/iio/industrialio-gts-helper.c
index 291c0fc332c9..602d3d338e66 100644
--- a/drivers/iio/industrialio-gts-helper.c
+++ b/drivers/iio/industrialio-gts-helper.c
@@ -4,6 +4,7 @@
* Copyright (c) 2023 Matti Vaittinen <mazziesaccount@xxxxxxxxx>
*/
+#include <linux/cleanup.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/export.h>
@@ -167,8 +168,8 @@ static int iio_gts_gain_cmp(const void *a, const void *b)
static int gain_to_scaletables(struct iio_gts *gts, int **gains, int **scales)
{
- int i, j, new_idx, time_idx, ret = 0;
- int *all_gains;
+ int ret, i, j, new_idx, time_idx;
+ int *all_gains __free(kfree) = NULL;
See the docs in cleanup.h (added recently).
Constructor and destructor should go together. Dan wrote good docs on this
(which are now in cleanup.h) so I'll not go into why!
I went through the cleanup.h, and noticed the nice explanation for the
pitfall where we have multiple "scoped operations" with specific
ordering required. I didn't see other reasoning beyond that - I do hope
I didn't miss anything.
I find introducing variables mid-function very confusing. Only exception
for this has been introducing temporary variables at the start of a
block, to reduce the scope. I would still like to avoid this when it
isn't absolutely necessary, as it bleeds my eyes :)
I really don't see why we would have other cleanups which required
specific ordering with the allocated "all_gains".
Anyways, if you think we really have a problem here, would it then
suffice if I moved the:
gain_bytes = array_size(gts->num_hwgain, sizeof(int));
all_gains = kcalloc(gts->num_itime, gain_bytes, GFP_KERNEL);
if (!all_gains)
return -ENOMEM;
to the beginning of the function, and the "int *all_gains __free(kfree)
= NULL;" as last variable declaration?
(This is not optimal as we will then do the allocation even if
converting gains to scales failed - but I don't think this is a real
problem as this should never happen after the driver is proven working
for the first time).
Upshot is this goes where you do the kcalloc, not up here.
*whining* "but, but, but ... it is ugly..." :)
Yours,
-- Matti
