On 04/17/18 13:55, Mauro Carvalho Chehab wrote:
> Em Tue, 17 Apr 2018 11:59:40 +0200
> Hans Verkuil <hverk...@xs4all.nl> escreveu:
>
>> On 04/16/18 21:41, Hans Verkuil wrote:
>>> On 04/16/2018 08:09 PM, Mauro Carvalho Chehab wrote:
>>>> Em Mon, 16 Apr 2018 15:03:35 -0300
>>>> Mauro Carvalho Chehab <mche...@s-opensource.com> escreveu:
>>>>
>>>>> Em Mon, 16 Apr 2018 15:21:18 +0200
>>>>> Hans Verkuil <hverk...@xs4all.nl> escreveu:
>>>>>
>>>>>> From: Hans Verkuil <hansv...@cisco.com>
>>>>>>
>>>>>> The v2 pad structure never exposed the pad index, which made it
>>>>>> impossible
>>>>>> to call the MEDIA_IOC_SETUP_LINK ioctl, which needs that information.
>>>>>>
>>>>>> It is really trivial to just expose this information, so implement this.
>>>>>>
>>>>>
>>>>> Acked-by: Mauro Carvalho Chehab <mche...@s-opensource.com>
>>>>
>>>> Err... I looked on it too fast... See my comments below.
>>>>
>>>> The same applies to patch 8/9.
>>>>
>>>>>>
>>>>>> Signed-off-by: Hans Verkuil <hansv...@cisco.com>
>>>>>> ---
>>>>>> drivers/media/media-device.c | 1 +
>>>>>> include/uapi/linux/media.h | 7 ++++++-
>>>>>> 2 files changed, 7 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
>>>>>> index dca1e5a3e0f9..73ffea3e81c9 100644
>>>>>> --- a/drivers/media/media-device.c
>>>>>> +++ b/drivers/media/media-device.c
>>>>>> @@ -331,6 +331,7 @@ static long media_device_get_topology(struct
>>>>>> media_device *mdev,
>>>>>> kpad.id = pad->graph_obj.id;
>>>>>> kpad.entity_id = pad->entity->graph_obj.id;
>>>>>> kpad.flags = pad->flags;
>>>>>> + kpad.index = pad->index;
>>>>>>
>>>>>> if (copy_to_user(upad, &kpad, sizeof(kpad)))
>>>>>> ret = -EFAULT;
>>>>>> diff --git a/include/uapi/linux/media.h b/include/uapi/linux/media.h
>>>>>> index ac08acffdb65..15f7f432f808 100644
>>>>>> --- a/include/uapi/linux/media.h
>>>>>> +++ b/include/uapi/linux/media.h
>>>>>> @@ -310,11 +310,16 @@ struct media_v2_interface {
>>>>>> };
>>>>>> } __attribute__ ((packed));
>>>>>>
>>>>>> +/* Appeared in 4.18.0 */
>>>>>> +#define MEDIA_V2_PAD_HAS_INDEX(media_version) \
>>>>>> + ((media_version) >= 0x00041200)
>>>>>> +
>>>>
>>>> I don't like this, for a couple of reasons:
>>>>
>>>> 1) it has a magic number on it, with is actually a parsed
>>>> version of LINUX_VERSION() macro;
>>>
>>> I can/should change that to KERNEL_VERSION().
>
> I don't think so. The macro is not there at include/uapi.
>
>>>
>>>>
>>>> 2) it sounds really weird to ship a header file with a new
>>>> kernel version meant to provide backward compatibility with
>>>> older versions;
>>>>
>>>> 3) this isn't any different than:
>>>>
>>>> #define MEDIA_V2_PAD_HAS_INDEX -1
>>>>
>>>> I think we need to think a little bit more about that.
>>>
>>> What typically happens is that applications (like those in v4l-utils
>>> for example) copy the headers locally. So they are compiled with the headers
>>> of a specific kernel version, but they can run with very different kernels.
>>>
>>> This is normal for distros where you can install different kernel versions
>>> without needing to modify applications.
>>>
>>> In fact, we (Cisco) use the latest v4l-utils code on kernels ranging between
>>> 2.6.39 to 4.10 (I think that's the latest one in use).
>
> Well, if you use a macro, the "compat" code at v4l-utils (or whatever other
> app you use) will be assuming the specific Kernel version you used when you
> built it, with is probably not what you want.
>
> The way of checking if a feature is there or not is, instead, to ask for
> the media version via MEDIA_IOC_DEVICE_INFO. It should provide the
> media API version.
>
> This is already filled with:
> info->media_version = LINUX_VERSION_CODE;
>
> So, all we need to do is to document that the new fields are available only
> for such version or above and add such check at v4l-utils.
Yes, and that's what you stick in the macro argument:
ioctl(fd, MEDIA_IOC_DEVICE_INFO, &info);
if (MEDIA_V2_PAD_HAS_INDEX(info.media_version)) {
// I can use the index field
}
I think I did not document this clearly.
Regards,
Hans
>
>>>
>>> The media version tells you whether or not the kernel supports this feature.
>>> I don't see another way of doing this.
>>>
>>> In most other cases we can just say that if the field value is 0, then it
>>> should not be used. Unfortunately, 0 is a valid value for the pad index, for
>>> the entity flags and for the entity function (some drivers set it to
>>> MEDIA_ENT_F_UNKNOWN, which has value 0). This last one is most unfortunate,
>>> since this should never have happened and would have been detected if we had
>>> proper compliance tools.
>>
>> Actually, I think that if I first ensure that all drivers correctly set
>> function
>> to a non-zero value, then there is no need for a test macro and I can just
>> say
>> that if it is 0, then fall back to 'type'.
>>
>> It requires some analysis, but it's doable.
>
> That is something that we want to do anyway.
>>
>> For the index and flags field there is no alternative that I can think of,
>> though.
>>
>> Regards,
>>
>> Hans
>>
>>>
>>> Regards,
>>>
>>> Hans
>>>
>>>>
>>>>
>>>>>> struct media_v2_pad {
>>>>>> __u32 id;
>>>>>> __u32 entity_id;
>>>>>> __u32 flags;
>>>>>> - __u32 reserved[5];
>>>>>> + __u32 index;
>>>>>> + __u32 reserved[4];
>>>>>> } __attribute__ ((packed));
>>>>>>
>>>>>> struct media_v2_link {
>>>>>
>>>>>
>>>>>
>>>>> Thanks,
>>>>> Mauro
>>>>
>>>>
>>>>
>>>> Thanks,
>>>> Mauro
>>>>
>>>
>>
>
>
>
> Thanks,
> Mauro
>
