Re: [PATCH] media: soc-camera: support deferred probing of clients and OF cameras

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On Mon, Feb 10, 2014 at 10:37 PM, Guennadi Liakhovetski
<g.liakhovetski@xxxxxx> wrote:
> Hi Bryan,
>
> On Mon, 10 Feb 2014, Bryan Wu wrote:
>
>> On Sun, Feb 9, 2014 at 2:20 PM, Guennadi Liakhovetski
>> <g.liakhovetski@xxxxxx> wrote:
>> > Hi Bryan,
>> >
>> > Thanks for reiterating this patch!
>> >
>>
>> Sure, my pleasure. I basically assembled your patches together and
>> change them to use latest V4L2 soc_camera API.
>>
>> > On Fri, 7 Feb 2014, Bryan Wu wrote:
>
> [snip]
>
>> >> @@ -67,6 +81,8 @@ struct soc_camera_async_client {
>> >>
>> >>  static int soc_camera_video_start(struct soc_camera_device *icd);
>> >>  static int video_dev_create(struct soc_camera_device *icd);
>> >> +static void soc_camera_of_i2c_info(struct device_node *node,
>> >> +                               struct soc_camera_of_client *sofc);
>> >
>> > If you have to resubmit this patch, plase, make sure the second line of
>> > the above declaration is aligned af usual - under the first character
>> > _after_ the opening bracket.
>> >
>>
>> No problem, I will update this.
>> Hmmm, something weird on my side. I did put the second line starting
>> under the first character after the opening bracket. But in git show
>> and git format-patch I got this
>> ---
>> static int soc_camera_video_start(struct soc_camera_device *icd);
>>  static int video_dev_create(struct soc_camera_device *icd);
>> +static void soc_camera_of_i2c_info(struct device_node *node,
>> +                                  struct soc_camera_of_client *sofc);
>> ---
>>
>> But I think that's what you want, right?
>
> Don't know - now aöö TABs above are replaced with spaces, so, cannot say.
>
> [snip]
>
>> >> +{
>> >> +     struct soc_camera_of_client *sofc;
>> >> +     struct soc_camera_desc *sdesc;
>> >
>> > I'm really grateful, that you decided to use my original patch and
>> > preserve my authorship! But then, I think, it'd be also better to avoid
>> > unnecessary changes to it. What was wrong with allocation of *sofc in the
>> > definition line?
>> >
>>
>> Oh, this is really I want to bring up. It's a very subtle bug here.
>>
>> If we use local variable sofc instead of zalloc, fields of sofc have
>> undetermined None NULL value.
>
> No. If you initialise some members of a struct in its definition line, the
> rest will be initialised to 0 / NULL. I.e. in
>
>         struct foo y = {.x = 1,};
>
> all other fields of y will be initialised to 0.

I see, but original one is soc_camera_link which is simple in this
case. right now we move to soc_camera_desc. I think following line is
not very straight forward in a local function.

struct soc_camera_desc sdesc = { .host_desc = { .host_wait = true,},};

What about
a) struct soc_camera_desc sdesc and use memset to all 0.
b) use kzalloc() and kfree() in this function.

I think b) is more straight forward and easy to understand.

Thanks,
-Bryan
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