Hi
On 2023/7/17 17:43, Lucas Stach wrote:
Hi Jingfeng,
Am Freitag, dem 23.06.2023 um 18:08 +0800 schrieb Sui Jingfeng:
From: Sui Jingfeng <suijingfeng@xxxxxxxxxxx>
Because the etnaviv_gem_new_private() function receives the size_t argument
for the number of pages. And the number of pages should be unsigned.
Note that Most 32-bit architectures use "unsigned int" size_t,
and all 64-bit architectures use "unsigned long" size_t.
So, let's keep the argument and parameter consistent.
This explanation doesn't add up. npages is just that: a number of
pages. Why would it make sense to use size_t here?
Because the 'size' variable in the etnaviv_gem_prime_import_sg_table()
function is declared
as size_t type. On 64-bit machine, size_t is actually is 64-bit wide and
it is *unsigned*.
While 'int' is actually 32-bit wide(at both 32-bit system and 64-bit
system) and it is *signed*,
So, my point (argument) is that
1) This patch help to avoid the unnecessary 64 bit to 32 bit conversion.
2) The kvmalloc_array() function also accept size_t type (see the
prototype of kvmalloc_array function include/linux/slab.h)
So my patch do helps to keep the code style consistent.
If you want to be consistent I would have expected this change to
switch things to unsigned int,
This may introduce a truncate operation (from a 64-bit to 32-bit), which
is necessary.
And when you pass the 'npages' parameter to kvmalloc_array() function,
The compiler probably has to do the integer promotion (from a 32-bit to
64-bit) for you.
as you did in the second patch of this
series.
Regards,
Lucas
Signed-off-by: Sui Jingfeng <suijingfeng@xxxxxxxxxxx>
---
drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c b/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c
index 3524b5811682..b003481adc2b 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c
@@ -114,7 +114,8 @@ struct drm_gem_object *etnaviv_gem_prime_import_sg_table(struct drm_device *dev,
{
struct etnaviv_gem_object *etnaviv_obj;
size_t size = PAGE_ALIGN(attach->dmabuf->size);
- int ret, npages;
+ size_t npages = size / PAGE_SIZE;
+ int ret;
ret = etnaviv_gem_new_private(dev, size, ETNA_BO_WC,
&etnaviv_gem_prime_ops, &etnaviv_obj);
@@ -123,8 +124,6 @@ struct drm_gem_object *etnaviv_gem_prime_import_sg_table(struct drm_device *dev,
lockdep_set_class(&etnaviv_obj->lock, &etnaviv_prime_lock_class);
- npages = size / PAGE_SIZE;
-
etnaviv_obj->sgt = sgt;
etnaviv_obj->pages = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
if (!etnaviv_obj->pages) {
