Em 13-01-2011 01:05, Pawel Osciak escreveu:
> Hi Mauro,
>
> On Wed, Jan 12, 2011 at 10:49, Mauro Carvalho Chehab <[email protected]>
> wrote:
>> Em 12-01-2011 08:25, Marek Szyprowski escreveu:
>>> Hello Mauro,
>>>
>>> I've rebased our fimc and saa patches onto
>>> http://linuxtv.org/git/mchehab/experimental.git
>>> vb2_test branch.
>>
>> Thanks!
>>
>> As before, I'll be commenting the patches as I'll be seeing any issues.
>>
>>> Pawel Osciak (2):
>>> Fix mmap() example in the V4L2 API DocBook
>>
>> In fact, the check for retval < 0 instead of retval == -1 is not a fix.
>> According with
>> mmap man pages:
>> RETURN VALUE
>> On success, mmap() returns a pointer to the mapped area. On
>> error, the value MAP_FAILED (that is, (void *) -1) is returned, and errno
>> is set appropriately. On success, munmap() returns 0, on
>> failure -1, and errno is set (probably to EINVAL).
>>
>> The change is not wrong, as -1 is lower than 0, but using -1 is more
>> compliant with
>> libc. So, I'll be applying just the CodingStyle fixes on it.
>
> Sorry, but I think you got it wrong. The example is called "mmap()
> example". But I did not change return value checking of mmap() calls.
> I changed return value checking of ioctl() calls. So I believe the
> patch is correct.
>From ioctl man page:
RETURN VALUE
Usually, on success zero is returned. A few ioctl() requests use the
return value as an output parameter and return a non-negative value on
success. On error, -1 is returned, and errno is set appropriately.
So, at least on glibc, it will return -1 for errors, storing the error code at
errno
var, and 0 for OK.
Several V4L2 applications do error checks with -1. So, if some non-glibc
implementation
is returning a different return value, that means that several V4L applications
will
not work properly. Do you know any case where ioctl is implemented on a
different way?
Cheers,
Mauro.
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