[bug report] drm/prime: replace NULL with error value in drm_prime_pages_to_sg

[Oleksandr Andrushchenko]

On 06/15/2018 12:08 PM, Dan Carpenter wrote:
> On Fri, Jun 15, 2018 at 08:39:17AM +0300, Oleksandr Andrushchenko wrote:
>> On 06/15/2018 06:22 AM, YoungJun Cho wrote:
>>> 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 at oracle.com
>>> <mailto:dan.carpenter at oracle.com>> 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.
>>>
>> I believe it is safe to change the return value to error pointer:
>> the code below (which is the only caller of .gem_prime_get_sg_table
>> callback) does not check for NULL anyways
>>
>> Dan, do you want me to send the patch for Xen or you prefer to post both
>> Xen and CMA helpers fix yourself?
> Can you do it and give me a Reported-by tag?
Sure
> regards,
> dan carpenter
>