On Tue, Oct 10, 2023 at 03:22:56PM +0200, Thierry Reding wrote: > On Mon, Jun 26, 2023 at 10:33:30PM +0800, Sui Jingfeng wrote: > > Return -ENOMEM if tegra_bo_mmap() fails. > > > > Signed-off-by: Sui Jingfeng <suijingfeng@xxxxxxxxxxx> > > --- > > drivers/gpu/drm/tegra/gem.c | 2 ++ > > 1 file changed, 2 insertions(+) > > Sorry, this fell through the cracks. I think it'd be better if > tegra_bo_mmap() were to be improved to always return either an ERR_PTR() > encoded error code or a valid pointer. Throwing NULL into the mix isn't > useful because it typically means something like -ENOMEM anyway. Error > codes are more explicit, so since we're already using them for some > cases, might as well return them for all. > > Actually, looks like tegra_bo_mmap() never actually returns an ERR_PTR() > encoded error code. It's either obj->vaddr, the return value of vmap() > (which is either NULL or the address of the mapping), or the address > obtained from dma_buf_vmap_unlocked() (i.e. map.vaddr) or NULL on > failure. So I think it would equally make sense to keep your patch and > to remove the IS_ERR() check below it. > > I would slightly prefer the first option, but either is fine. How about the attached patch? Thierry
From b34a09efcf7b1d2c25d3baf8c6d91c5ca09b4e0f Mon Sep 17 00:00:00 2001
From: Thierry Reding <treding@xxxxxxxxxx>
Date: Tue, 10 Oct 2023 17:26:14 +0200
Subject: [PATCH] drm/tegra: gem: Do not return NULL in tegra_bo_mmap()
It's confusing for a function to return NULL and ERR_PTR()-encoded error
codes on failure. Make sure we only ever return the latter since that's
what callers already expect.
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
drivers/gpu/drm/tegra/gem.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
index 11296de59c5a..679460e05c05 100644
--- a/drivers/gpu/drm/tegra/gem.c
+++ b/drivers/gpu/drm/tegra/gem.c
@@ -178,6 +178,7 @@ static void *tegra_bo_mmap(struct host1x_bo *bo)
{
struct tegra_bo *obj = host1x_to_tegra_bo(bo);
struct iosys_map map;
+ void *vaddr;
int ret;
if (obj->vaddr)
@@ -185,10 +186,18 @@ static void *tegra_bo_mmap(struct host1x_bo *bo)
if (obj->gem.import_attach) {
ret = dma_buf_vmap_unlocked(obj->gem.import_attach->dmabuf, &map);
- return ret ? NULL : map.vaddr;
+ if (ret < 0)
+ return ERR_PTR(ret);
+
+ return map.vaddr;
}
- return vmap(obj->pages, obj->num_pages, VM_MAP, pgprot_writecombine(PAGE_KERNEL));
+ vaddr = vmap(obj->pages, obj->num_pages, VM_MAP,
+ pgprot_writecombine(PAGE_KERNEL));
+ if (!vaddr)
+ return -ENOMEM;
+
+ return vaddr;
}
static void tegra_bo_munmap(struct host1x_bo *bo, void *addr)
--
2.42.0
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