Re: [GIT PULL] Selection API and fixes for v3.2

[Mauro Carvalho Chehab <mchehab@redhat.com>]

Em 26-09-2011 08:21, Marek Szyprowski escreveu:
> Hello,
> 
> On Monday, September 26, 2011 1:14 PM Mauro Carvalho Chehab wrote:
> 
>>> Scott Jiang (1):
>>>       vb2: add vb2_get_unmapped_area in vb2 core
>>
>>> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
>>> index ea55c08..977410b 100644
>>> --- a/include/media/videobuf2-core.h
>>> +++ b/include/media/videobuf2-core.h
>>> @@ -309,6 +309,13 @@ int vb2_streamon(struct vb2_queue *q, enum v4l2_buf_type type);
>>>  int vb2_streamoff(struct vb2_queue *q, enum v4l2_buf_type type);
>>>
>>>  int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma);
>>> +#ifndef CONFIG_MMU
>>> +unsigned long vb2_get_unmapped_area(struct vb2_queue *q,
>>> +				    unsigned long addr,
>>> +				    unsigned long len,
>>> +				    unsigned long pgoff,
>>> +				    unsigned long flags);
>>> +#endif
>>>  unsigned int vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait);
>>>  size_t vb2_read(struct vb2_queue *q, char __user *data, size_t count,
>>>  		loff_t *ppos, int nonblock);
>>
>> This sounds me like a hack, as it is passing the problem of working with a non-mmu
>> capable hardware to the driver, inserting architecture-dependent bits on them.
>>
>> The proper way to do it is to provide a vb2 core support to handle the non-mmu case
>> inside it.
> 
> This is exactly what this patch does - it provides generic vb2 implementation for 
> fops->get_unmapped_area callback which any vb2 ready driver can use. This operation
> is used only on NON-MMU systems. Please check drivers/media/video/v4l2-dev.c file and
> the implementation of get_unmapped_area there. Similar code is used by uvc driver.

At least there, there is a:
#ifdef CONFIG_MMU
#define v4l2_get_unmapped_area NULL
#else
...
#endif

block, so, in thesis, a driver can be written to support both cases without inserting
#ifdefs inside it.

Ideally, I would prefer if all those iommu-specific calls would be inside the core.
A driver should not need to do anything special in order to support a different
(sub)architecture.


> 
> Best regards