Re: [REVIEWv2 PATCH for v3.15 2/4] videobuf2-core: fix sparse errors.

[Hans Verkuil <hverkuil@xs4all.nl>]

On 03/17/2014 01:26 PM, Laurent Pinchart wrote:
> Hi Hans,
> 
> Thank you for the patch.
> 
> On Monday 17 March 2014 11:58:08 Hans Verkuil wrote:
>> (Fixed typo pointed out by Pawel, but more importantly made an additional
>> change to __qbuf_dmabuf. See last paragraph in the commit log)
> 
> [snip]
> 
>> I made one other change: in __qbuf_dmabuf the result of the memop call
>> attach_dmabuf() is checked by IS_ERR() instead of IS_ERR_OR_NULL(). Since
>> the call_ptr_memop macro checks for IS_ERR_OR_NULL and since a NULL pointer
>> makes no sense anyway, I've changed the IS_ERR to IS_ERR_OR_NULL to remain
>> consistent, both with the call_ptr_memop macro, but also with all other
>> cases where a pointer is checked.
> 
> Could you please split this to a separate patch ?
> 
>> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
>> ---
>>  drivers/media/v4l2-core/videobuf2-core.c | 215 +++++++++++++++++-----------
>>  1 file changed, 132 insertions(+), 83 deletions(-)
>>
>> diff --git a/drivers/media/v4l2-core/videobuf2-core.c
>> b/drivers/media/v4l2-core/videobuf2-core.c index f9059bb..fb1ee86 100644
>> --- a/drivers/media/v4l2-core/videobuf2-core.c
>> +++ b/drivers/media/v4l2-core/videobuf2-core.c
> 
> [snip]
> 
>> @@ -1401,12 +1458,11 @@ static int __qbuf_dmabuf(struct vb2_buffer *vb,
>> const struct v4l2_buffer *b) memset(&vb->v4l2_planes[plane], 0,
>> sizeof(struct v4l2_plane));
>>
>>  		/* Acquire each plane's memory */
>> -		mem_priv = call_memop(vb, attach_dmabuf, q->alloc_ctx[plane],
>> +		mem_priv = call_ptr_memop(vb, attach_dmabuf, q->alloc_ctx[plane],
>>  			dbuf, planes[plane].length, write);
>> -		if (IS_ERR(mem_priv)) {
>> +		if (IS_ERR_OR_NULL(mem_priv)) {
>>  			dprintk(1, "qbuf: failed to attach dmabuf\n");
>> -			fail_memop(vb, attach_dmabuf);
>> -			ret = PTR_ERR(mem_priv);
>> +			ret = mem_priv ? PTR_ERR(mem_priv) : -EINVAL;
> 
> That gets confusing. Wouldn't it be better to switch the other memop calls 
> that return pointers to return an ERR_PTR() in error cases instead of NULL ?

I don't see why it is confusing as long as everyone sticks to the same scheme.
I actually prefer this way, since it is more robust as it will catch cases
where the memop unintentionally returned NULL. If I would just check for IS_ERR,
then that would be missed. Especially in a core piece of code like this I'd
like to err on the robust side.

Regards,

	Hans

> 
>>  			dma_buf_put(dbuf);
>>  			goto err;
>>  		}
>