Dear Dan,
Your mail flashes back to my memory 5 years ago.
Back then, I had cleaned up the exynos driver.
And the replacement IS_ERR was one of items.
IMHO it is still better to modify those two functions, drm_gem_cma_prime_get_sg_table and xen_drm_front_gem_get_sg_table.
Thank you.
Best regards YJ
On Thu, 14 Jun 2018, 23:42 Dan Carpenter, <dan.carpenter@xxxxxxxxxx> wrote:
Hello YoungJun Cho,
The patch 7e3d88f9cce3: "drm/prime: replace NULL with error value in
drm_prime_pages_to_sg" from Jun 24, 2013, leads to the following
static checker warning:
drivers/gpu/drm/drm_prime.c:317 drm_gem_map_dma_buf()
warn: 'sgt' can also be NULL
drivers/gpu/drm/drm_prime.c
307 /*
308 * two mappings with different directions for the same attachment are
309 * not allowed
310 */
311 if (WARN_ON(prime_attach->dir != DMA_NONE))
312 return ERR_PTR(-EBUSY);
313
314 sgt = obj->dev->driver->gem_prime_get_sg_table(obj);
The problematic functions here are drm_gem_cma_prime_get_sg_table() and
xen_drm_front_gem_get_sg_table(). My preference would be to update
those functions to return error pointers, but I'm not familiar with the
code or able to test it.
But this static checker test seems pretty good so I'm likely to publish
it soon and then this sort of bug will normally be caught quickly.
315
316 if (!IS_ERR(sgt)) {
317 if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir,
318 DMA_ATTR_SKIP_CPU_SYNC)) {
319 sg_free_table(sgt);
320 kfree(sgt);
321 sgt = ERR_PTR(-ENOMEM);
322 } else {
323 prime_attach->sgt = sgt;
324 prime_attach->dir = dir;
325 }
326 }
327
328 return sgt;
regards,
dan carpenter
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