From: Thierry Reding <thierry.reding@gmail.com>
To: Sui Jingfeng <suijingfeng@loongson.cn>
Cc: Mikko Perttunen <mperttunen@nvidia.com>,
David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
Jonathan Hunter <jonathanh@nvidia.com>,
dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] drm/tegra: Return an error code if fails
Date: Tue, 10 Oct 2023 17:31:33 +0200 [thread overview]
Message-ID: <ZSVuVcqdGfGtQIQj@orome.fritz.box> (raw)
In-Reply-To: <ZSVQMPuRnXzC0lgf@orome.fritz.box>
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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@loongson.cn>
> > ---
> > 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
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From b34a09efcf7b1d2c25d3baf8c6d91c5ca09b4e0f Mon Sep 17 00:00:00 2001
From: Thierry Reding <treding@nvidia.com>
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@nvidia.com>
---
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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next prev parent reply other threads:[~2023-10-10 15:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-26 14:33 [PATCH 1/2] drm/tegra: Return an error code if fails Sui Jingfeng
2023-06-26 14:33 ` [PATCH 2/2] drm/tegra: Remove surplus else after return Sui Jingfeng
2023-10-10 15:28 ` Thierry Reding
2023-07-27 10:02 ` [1/2] drm/tegra: Return an error code if fails suijingfeng
2023-10-10 13:22 ` [PATCH 1/2] " Thierry Reding
2023-10-10 15:31 ` Thierry Reding [this message]
2023-10-11 3:06 ` Sui Jingfeng
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